Nature-based green infrastructure: A review of African experience and potential

Dupar, Mairi; Henriette, Elvina; Hubbard, Eric Research Report Nature-based green infrastructure: A review of African experience and potential ODI Report Provided in Cooperation with: ODI Global, London Suggested Citation: Dupar, Mairi; Henriette, Elvina; Hubbard, Eric (2023) : Nature-based green infrastructure: A review of African experience and potential, ODI Report, Overseas Development Institute (ODI), London This Version is available at: https://hdl.handle.net/10419/280308 Standard-Nutzungsbedingungen: Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden. Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen. 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If the documents have been made available under an Open Content Licence (especially Creative Commons Licences), you may exercise further usage rights as specified in the indicated licence. https://creativecommons.org/licenses/by-nc-nd/4.0/ Nature-based green infrastructure: A review of African experience and potential Mairi Dupar, Elvina Henriette and Eric Hubbard June 2023 Series Report Readers are encouraged to reproduce material for their own publications, as long as they are not being sold commercially. ODI requests due acknowledgement and a copy of the publication. Foronline use, we ask readers to link to the original resource on the ODI website. The views presented in this paper are those of the author(s) and do not necessarily represent the views of ODI, our funders or our partners. This work is licensed under CC BY-NC-ND 4.0. How to cite: Dupar, M., Henriette, H. and Hubbard, E. (2023) Nature-based green infrastructure: A review of African experience and potential. ODI: London. Photo front cover: UNEP Funded by Acknowledgements The authors are grateful for the support and expert comments of Tremayne Stanton-Kennedy, Ina Porras and Mark Harvey. We also thank Jessy Appavoo, Chris Henderson, Nadia Sitas, Paul Sawyers, Laetitia Pettinotti and Adriana Quevedo for their helpful comments and guidance. Special thanks to Laetitia Pettinotti for integration of the finance text in this volume with the sister publication: Pettinotti, L. and Quevedo, A. (2023) Mapping finance sources for nature-based solutions in Africa. London: ODI. Thanks also to Donald Barclay and Shanice Mohanlal of SouthSouthNorth for coordination, and to Green Ink for editing and design. About the authors Mairi Dupar is a senior researcher at ODI, focusing on climate risk and ecosystem-based adaptation (ORCID: 0000-0001-7383-9251). Elvina Henriette is a conservation biologist who works as Programme Manager at TRASS – Terrestrial Restoration Action Society of Seychelles. Eric Hubbard serves as the Africa Regional Focal Point at the Urban Biodiversity Hub and co-leads the NATURA Network Africa Regional Team for the production of the Global NBS Roadmap. Eric is a Senior Advisor to the Mayor of Freetown and Freetown City Council. Contents Acknowledgements / i Glossary of frequently used terms / v Summary / 1 Why nature-based solutions for green infrastructure? / 1 How can nature-based solutions for green infrastructure be useful in African contexts? / 1 What do we know about the use of nature-based solutions for green infrastructure in Africa? / 2 What do we not yet know about the use of nature-based solutions for green infrastructure in Africa? / 3 Recommendations / 5 Recommendations for national and local governments and regional bodies / 5 Recommendations for donors and development partners / 5 Recommendations for researchers / 6 1 Introduction / 7 About this report / 7 The context: Africa’s infrastructure needs / 7 Structure of this report / 8 2 Global perspectives on understanding and managing ecosystem services / 11 Valuing nature / 11 Assessing infrastructure options: grey versus green / 12 Assessing infrastructure options: governance and processes / 15 When NBS-GI is not sufficient / 18 The critical issue of maintenance / 18 3 African perspectives on understanding and managing ecosystem services / 20 Data and mapping of ecosystem services in Africa to support decision-making: an overview / 20 Valuation and options assessment in Africa / 21 Financing nature-based green infrastructure in Africa / 22 Understanding the cost-effectiveness of NBS-GI in Africa / 23 4 Nature-based green infrastructure in practice: case studies / 25 NBS-GI for riverine flood risk reduction / 25 NBS-GI for water supply and wastewater management / 33 NBS-GI for air quality including localised PM2.5 and PM10 mitigation / 40 NBS-GI for agricultural productivity, including soil fertility / 40 NBS-GI for marine and coastal fisheries productivity / 43 NBS-GI for cooling services and heat reduction in open spaces / 54 NBS-GI for human mobility in the urban environment / 72 Conclusions / 73 How NBS-GI are prioritised and selected / 73 How NBS-GI solutions are financed / 74 The effectiveness of NBS-GI / 75 Areas for further investigation / 77 Annex: Defining nature-based solutions and green infrastructure / 78 Nature-based versus nature-derived and nature-inspired / 78 Other preferred terms apart from ‘nature-based solutions’ / 78 Annex: Methods of the present study / 80 Endnotes / 83 Glossary of frequently used terms Biodiversity – The variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystems and the ecological complexes of which they are part.1 Ecosystem – A dynamic complex of plant, animal and microorganism communities and their nonliving environment interacting as a functional unit.2 Ecosystem services – The benefits and disbenefits people obtain from ecosystems now and in the future. In the Millennium Ecosystem Assessment, ecosystem services were divided into provisioning, regulating, cultural and supporting services. Source: Millennium Ecosystem Assessment (2005). This classification was superseded in assessments by the Intergovernmental Platform for Biodiversity and Ecosystem Services (IPBES), which use ‘Nature’s contributions to people’. This is because IPBES recognises that many ecosystem services fit into more than one of the four categories. For example, food is both a provisioning service and, in many cultures, it provides a significant cultural service.3 Green infrastructure – Infrastructure that uses or harnesses ecological functions for the benefit of societies. This is the meaning of the term ‘nature-based solutions for green infrastructure’ (NBS-GI) in this report, which aligns with United Kingdom government use.4 Grey-green infrastructure – Infrastructure that incorporates both built elements (often involving concrete, steel and other hard-engineered materials and structures) as well as natural elements such as management of wetlands, forest and agricultural land and planted features in urban areas. Provisioning services Products obtained from ecosystems • food • fresh water • fuelwood • fiber • biochemicals • generic resources Supporting services Services necessary for the production of all other ecosystems services • Soil formation • Nutrient cycling • Primary production Regulating services Benefits obtained from regulation of ecosystem processes • climate regulation • disease regulation • water regulation • water purification • pollination Cultural services Nonmaterial benefits obtained from ecosystems • spiritual and religious • recreation and ecotourism • aesthetic • inspirational • educational • sense of place • cultural heritage Nature-based solutions – Nature-based solutions (NBS) are defined by the World Conservation Union (IUCN) as‘actions to protect, sustainably manage, and restore natural or modified ecosystems to address societal challenges, simultaneously providing human well-being and biodiversity benefits’.5 The terms ‘NBS’ and ‘NBS-GI’ are used throughout this report. Please see the Annex for a detailed discussion of the term and alternatives such as ‘ecosystem-based adaptation’. Natural capital – The language of natural capital is based on accountancy. Natural capital assets such as land, oceans or minerals are referred to as ‘stocks’. The services derived from these stocks are called ‘flows’. These flows can be split into ecosystem and abiotic services. Ecosystem services are produced by living systems and include crops, pollination, water filtration and recreation. Abiotic services arise from geological processes and include minerals, oil, wind and tides.6 7ODI Report 1 Introduction About this report This report looks at the existing and potential role of NBS-GI on the African continent. Specifically, this report discusses the use of NBS-GI in Africa for achieving disaster risk management and climate change mitigation and adaptation, alongside wider development objectives in the following sectors anddomains: • climate-related DRR (including e.g. management of both riverine/inland flood risk and coastal flood risk, landslides, and other impacts arising from glacial melt, tropical storms, sea level rise hazards, etc.) • freshwater provision and wastewater management • cooling services • agricultural productivity • coastal fisheries productivity • mitigation of localised air pollution (i.e. particulate matter (PM)2.5, PM10 mitigation) • shelter: optimising building design • human mobility in the urban environment (e.g. including land use planning and management of transport corridors, recreational spaces; provision of quality of life for urban residents, often in combination with the other services mentioned here). The objective of the report is to compile and synthesise evidence on: • What is motivating the selection of NBS-GI investments in Africa? • How are NBS-GI are being applied in various African contexts at present? • Are NBS-GI interventions achieving their objectives? • What intended and unintended consequences are documented? • How are NBS-GI being financed? • What do these lessons suggest for the role of donors in considering their support for NBS-GI in African countries and regionally? The context: Africa’s infrastructure needs President Adesina of the African Development Bank has said that the African continent needs $68–108billion in new financing every year to bridge its critical infrastructure gaps and support the continent’s growth and development.7 The African Group of Negotiators on climate change told the United Nations Framework Convention on Climate Change (UNFCCC) Conference of the Parties (COP)26 that the continent will need a minimum of $100billion peryear, from 2025–2040, for investment in infrastructure that both enhances climate resilience and cuts or avoids greenhouse gas emissions.8 The International Monetary Fund (IMF) calculates that climate change adaptation alone will cost up to $50billion every year for Africa, equivalent to about 3% of regionalGDP.9 NBS-GI are accorded a high political priority by African leaders, as partial solutions to Africa’s intersecting crises of unfulfilled human development and climate change. African Union President Macky Sall of Senegal wrote, on the cusp of UNFCCC COP27, that in Africa: ‘Climate adaptation is… about harnessing nature to restore degraded ecosystems; introducing drought-resistant crops, accessible digital services for smallholder farmers and weather-proofing infrastructure; and creating new green jobs for young people. In short, if climate change mitigation is the only way to keep our planet liveable, climate adaptation is an opportunity to forge a new 8ODI Report climate-resilient development path for Africa – a path that is smarter, more effective, more efficient and more productive.’10 Of the Nationally Determined Contributions (national climate plans) submitted to the UNFCCC in 2020–2022, 85% of sub-Saharan African countries’ plans mention NBS-GI.11 Structure of this report An overarching observation of this study is that nature-based solutions for green infrastructure (NBS-GI), which harness ecological functions for societal benefit, fulfil multiple development, wellbeing and DRR objectives. Their multifunctionality is normally the reason for their selection by African institutions and communities. This introduces a structuring issue for the report: because the NBS-GI interventions described were intentionally designed to be multipurpose, they do not fit neatly into sectoral categories. The report has been organised to reflect this complexity. Chapter 2 provides a brief global overview of current concepts and practice in valuing ecosystem services and integrating the values of nature into decision-making; and on the perceived effectiveness of NBS-GI. Chapter 3 provides a regional overview of how ecosystem services have been understood, valued and integrated into decision-making processes in Africa. Chapter 4 describes how NBS-GI are situated and applied within each of the sectors or infrastructure service areas listed; together with a collection of case studies from diverse African contexts. Each case study is tagged for the relevant sectoral goals and ecosystem services harnessed (and noting that all case studies are multipurpose). The case studies are labelled for their contribution to: Disaster risk reduction: inland flood risk Disaster risk reduction: coastal flood risk Cooling services, heat modification Particulate matter and air quality improvement Disaster risk reduction: erosion, landslide risk Water sector: delivery of freshwater quality and flow regulation Water sector: wastewater filtering Agricultural land productivity Marine and coastal fisheries productivity Shelter: optimising building design Human mobility, safety and well-being in the urban environment 9ODI Report Figure 1 Case studies and documented NBS-GI benefits Disaster risk reduction: inland flood risk Water sector: delivery of freshwater quality and flow regulation Water sector: wastewater filtering ETHEKWINI MUNICIPALITY, SOUTH AFRICA Cooling services, heat modification Shelter: optimising building design CAIRO, EGYPT TAHIRY HONKO, MADAGASCAR Disaster risk reduction: coastal flood risk Marine and coastal fisheries productivity WADI EL KU, NORTH DARFUR, SUDAN Water sector: delivery of freshwater quality and flow regulation Agricultural land productivity DAR ES SALAAM, TANZANIA Disaster risk reduction: inland flood risk Cooling services, heat modification Human mobility, safety and well-being in the urban environment FREETOWN, SIERRA LEONE Disaster risk reduction: erosion, landslide risk Cooling services, heat modification Particulate matter and air quality improvement Disaster risk reduction: inland flood risk PRASLIN ISLAND, SEYCHELLES Disaster risk reduction: erosion, landslide risk Water sector: delivery of freshwater quality and flow regulation Marine and coastal fisheries productivity Disaster risk reduction: erosion, landslide risk Disaster risk reduction: coastal flood risk Agricultural land productivity GAZI BAY, KENYA Marine and coastal fisheries productivity Disaster risk reduction: coastal flood risk Disaster risk reduction: erosion, landslide risk Agricultural land productivity 10 ODI Report The case studies seek to uncover how African institutions and actors have: • evaluated options for infrastructure development at strategic decision-making stages • selected, planned, financed and delivered NBSGI or hybrid grey-green infrastructure solutions, including with the use of private finance • assessed and demonstrated the impact of NBSGI, including intended and unintended benefits and harms. Each case study also describes briefly the climate action context: NBS-GI may be designed for climate change mitigation or adaptation goals, or both, as part of a suite of development and DRR objectives. Indeed, societal responses to climate change in the land-based sectors have high potential to advance both adaptation and mitigation concurrently.12 The case studies exclude NBS-GI without a direct infrastructural element, such as education and literacy programmes, or programmes whose primary intention is for global carbon trading, rather than for providing local and regional infrastructure functions. Chapter 5 synthesises key lessons from the literature and case studies. It draws conclusions on: • when, where and how we observe NBS-GI being selected in African countries and localities • the involvement of public versus private sector actors in the different stages and types of NBS-GI • evidence of which criteria have been used to establish and measure effectiveness • common elements that underpin successful attainment of NBS-GI objectives, and other positive outcomes • observed strategies for addressing common challenges in NBS-GI implementation. 11 ODI Report 2 Global perspectives on understanding and managing ecosystem services Valuing nature At a global level, successive assessments have endeavoured to chart the status and trends in ecosystem services.13 Reviews have scrutinised how the global economic system values natural assets and how economic policy-making could be transformed to drive conservation and restoration of the natural environment.14 Analysis at global scale concludes that nature is far undervalued. The Dasgupta Review found: ‘Nature’s worth to society – the true value of the various goods and services it provides – is not reflected in market prices because much of it is open to all at no monetary charge. These pricing distortions have led us to invest relatively more in other assets, such as produced capital, and underinvest in our natural assets.’15 The Dasgupta Review further laid the blame on ‘deep-rooted, widespread institutional failure’.16 The OECD concludes that politics drives actors’ willingness to carry out valuations of nature and manage the negative environmental externalities of built development.17 The IPBES global assessment of the values of nature for people, approved by governments (July 2022), called for a global shift in values from individual material gains to ‘sustainability-aligned values’. IPBES proposes a five-step process for adequately valuing nature’s benefits in decisionmaking: ‘(i) constructing a legitimate process; (ii) defining the purpose of valuation; (iii) scoping the valuation; (iv) selecting and applying valuation methods; and (v)articulating the values into decision-making.’18 While IPBES identified approximately 50 systems for valuing nature more broadly, there is evidence of such tools being applied only 5% of the time.19 Governments fell far short of achieving the Convention on Biological Diversity’s global targets to 2020, known as the Aichi targets, including the target for integrating biodiversity values into planning.20 In summary, despite significant developments in assessing the status and trends of stocks and flows of ecosystem services and raising awareness of the intrinsic values of biodiversity and the values of nature to people, there is still a long way to go in integrating the valuation of ecosystem services into decision-making. The situation is concisely summarised by the Socio Ecological Research Lab as follows: ‘Since the publication of the Millennium Ecosystem Assessment and The Economics of Ecosystems and Biodiversity (TEEB), interest in ecosystem service assessment has grown exponentially in environmental science and policy. However, despite the academic progress, a key challenge to be addressed is developing a comprehensive assessment framework, in which biophysical, sociocultural, and monetary values can be properly combined. Although various conceptual frameworks integrate both the supply and the demand-sides of ecosystem 12 ODI Report services, few try to empirically operationalize a comprehensive ecosystem service assessment. Most of the ecosystem services literature has focused either on monetary valuation or on biophysical assessments, but there are few studies that empirically assess ecosystem services from an integrative approach.’ 21 Emergent initiatives are taking this integrative approach of biophysical ecosystem stocks and flows assessment together with the sociocultural (non-monetary) and monetary values in Idaho and Oklahoma, USA, and Andalucia, Spain. They require considerable philanthropic and public funding to be sustained.22 This context raises questions for the use of ecosystem valuations and linkages to decisionmaking in Africa, such as: • How much information about ecosystem stocks and flows is ‘enough’ to support decisionmaking that delivers the development and DRR benefits that society values and creates resilience for the future? • How can these processes be resourced? • Can these decision processes be opened for greater stakeholder access and understanding, including the possibility for co-production approaches where communities assert their values and preferences for managing and restoring ecosystems? • Are the benefits and disbenefits of both NBSGI and hard-engineered alternatives being adequately understood at decision stages, monitored and managed in implementation? These are questions that the African case studies in this report explore through empirical experience. Assessing infrastructure options: grey versus green Institutions are in many cases failing to incorporate the multidimensional benefits of NBSGI into options assessments. This is largely due to two tendencies: • decision-making at a narrow sectoral level, rather than at a strategic portfolio level • a reluctance to adopt environmental costbenefit assessment methods, and to rely instead on narrower, more conventional cost-benefit calculations. Infrastructure feasibility studies tend not to fully capture the potential negative environmental externalities of engineered, hard or ‘grey’ infrastructure projects in their cost-benefit analyses; they also tend to be driven by a single primary (often sectoral) infrastructure objective. Infrastructure feasibility studies tend not to evaluate fully all the positive externalities or benefits that interventions may create, beyond the primary intended objectives. They are often approached within a narrow project framework, rather than in a broader strategic, sustainable development framework. By contrast, NBS-GI tend to be evaluated and proposed based on a wider range of intended benefits, beyond a single infrastructural purpose. There is a shortcoming in ‘dominant valuation and accounting methodologies to value and account for benefits created by NBS-GI interventions’.23 In urban areas specifically, IPBES cites the two principal barriers to NBS-GI adoption as: (1) challenges in mobilising financing, particularly from the private sector and (2) challenges in adequate valuation of the multifunctional, multipurpose benefits of NBS-GI.24 13 ODI Report The management of riverine flood risk is an illustrative example. A conventional infrastructure solution could involve canalising a waterway: replacing the natural riverbank with concrete infrastructure, to control the water’s movement. Such measures may disrupt the sedimentation build up and flows and/or create ‘scouring’ (erosion) downstream, with knock-on effects on ecosystem users. If these downstream effects are not adequately evaluated during options assessment (including robust standards of social and environmental impact assessment) then the negative costs may not be well understood or acknowledged. These may include important harms and losses to biodiversity (such as habitat alteration for species) on which it is difficult to place a monetary value; there may also be economic losses (such as livelihood losses) or sociocultural losses (such as loss of recreational uses of ecosystems) implicated in grey infrastructure construction and maintenance, which are undervalued or ignored at options assessment phase. In the example of riverine flood risk management, an illustrative NBS-GI would be planting carefully selected indigenous vegetation species along the riverbank, to stabilise the underlying soil structures and reduce erosion and the transport of sediments. This might even be combined with such features as a ‘managed realignment’ (removal of hard infrastructure) from the bank to permit managed flooding over an area of land, where the use is suited to this purpose. The multiple purposes of such an NBS-GI may include, beyond flood risk management, erosion control, pollination services (based on plant species selected, with links to agricultural productivity) and livelihood benefits. Toxopeus and Polzin (2021)25 propose that strategies to overcome the undervaluation of NBS-GI benefits, in the project development context, should incorporate: improved data, evidence and metrics including through information and communications technologies; new valuation methods; new accounting frameworks that capture NBS-GI benefits; integrating accounting and assessment methods into decision-making. OECD (2018)26 charts the rise of ‘environmental cost-benefit accounting’, noting that the field is developing rapidly and producing more sophisticated methods for documenting the non-market values of various ecosystem services. The field is also making significant advances in valuing the social costs of carbon (i.e. quantifying the social damages incurred from greenhouse gas emissions). These methods reveal more clearly the negative externalities of many hardengineered infrastructure solutions in contrast with emissions-neutral or emissions-negative NBS-GI alternatives. Valuation methods that use people’s ‘stated preferences’ have been helpful in valuing both market and non-market values of nature within options assessment frameworks that precede financing.27 14 ODI Report Figure 2 The multifunctionality of nature-based interventions, across urban and rural areas Source: Place-based restoration approaches, actions and benefits: Figure 3, Global Land Outlook 2022 Efforts to establish common definitions and understandings of green infrastructure highlight their multifunctionality as their defining feature (see Figure 2 above).28 ‘Restoration is a proven and cost-effective solution to help reverse climate change and biodiversity loss caused by the rapid depletion of our finite natural capital stocks. Land restoration is broadly understood as a continuum of sustainable land and water management practices that can be applied to conserve or “rewild” natural areas, “up-scale” nature-positive food production in rural landscapes, and “green” urban areas, infrastructure, and supply chains.’29 An extensive exercise by UK BOND (British Overseas NGOs for Development), on the experience with NBS-GI across lowand middleincome countries concluded that actors should ‘prioritise multi-purpose NBS-GI at landscape scale and with a long-term vision’.30 All the case studies that BOND compiled showed that ‘NBS-GI need landscape/seascape multipurpose planning and management if they are to deliver large-scale and game-changing benefits for people, nature and climate. NBS-GI that have a narrow purpose and focus only on one type of land use can do more harm than good.’ The funding, conclude the authors, should follow these multifunctional landscape-level needs and be particularly targeted at the most vulnerable groups within landscapes. 15 ODI Report Strategic, multi-objective planning of this kind, within a long-term perspective, is known to be more appropriate in enabling communities and countries to adapt appropriately to climate change and avoid so-called ‘maladaptation’.31 The Intergovernmental Panel on Climate Change (IPCC) finds, with high scientific confidence, that actions that focus on single sectors or single risks and prioritise short-term gains often lead to maladaptation for ecosystems and people.32 The case studies identified during this study suggest that the ‘use cases’ for green infrastructure are likely to incorporate multiple social, economic and environmental objectives of this type. Significant budget and human resource is required to implement ecosystem services valuations, as part of a larger decision-making process. Valuation processes must be adequately funded, and often require complex quantitative work. In the context of generating project options for climate change adaptation and mitigation, the UNFCCC’s Paris Committee on Capacity Building has stressed how often developing countries, and particularly Least Developed Countries, lack the funding for feasibility assessments, including cost-benefit valuations and adequate stakeholder consultation.33 We revisit this question of the feasibility of, and modalities for, broader ecosystem services valuations (which ecosystem functions are valued, and how) in this report, through the prism of specific case studies. Assessing infrastructure options: governance and processes The evidence shows the importance of open and participatory modes of governance, including discursive processes to drive options assessment, planning and implementation. The selection of ‘decision support tools’ per se is only a small element of the whole. This finding is borne out by the present study and the many case examples it includes, and by IPCC assessments.34 There is a tendency to use consultants to compile data and produce studies on the status of natural capital, environmental degradation and the potential of nature-based green infrastructure to deliver multiple development and well-being functions, including in urban areas. Research institutes, universities and NGOs are also involved in many multi-stakeholder assessment, visioning and planning processes and are often eager to act as brokers for incorporating ‘invisible’ voices or for previously underacknowledged sources of compounding risk and vulnerability.35 Models are one tool for quantifying and mapping ecosystem stocks and flows. They are most useful when used to inform democratic decision-making processes. That is, they are useful in the context of a broader societal consultation or conversation about valuing the existing natural resources, and potentials for ecosystem service restoration and benefits-sharing among different social/ socioeconomic groups. Open, transparent cooperation among politicians, scientists, natural resource managers and users (in the broadest sense, incorporating farmers, forest users, community members as well as protected area managers, etc.) is essential. This can happen both in the data generation process (i.e. generating and validating data to feed into models) and at the options assessment phase that follows the modelling of present and future scenarios. There is impetus toward such ‘co-production’ processes, especially in densely-populated urban areas, to assess problems and map solutions.36 An in-depth case study is provided from the 16 ODI Report eThekwini Municipality in South Africa (page 26); co-production is also covered, with a lighter touch, in the Dar es Salaam and Freetown case studies (pages 56 and 62). Broadly defined, co-production refers to processes where scientifically produced data on observed and projected climate trends and climate impacts are tailored and targeted for the use of affected stakeholders in options assessment and planning processes. Stakeholders are invited to interrogate and validate scientifically derived data, analysis and recommendations and contribute their own local data and knowledge, before participating in varying degrees in options assessment processes. ‘Whilst co-production is relatively new in the field of climate change, it has a longer history in other fields where producing salient, credible and legitimate information can be improved by the involvement of users in the process.’37 In the case studies that follow, we specifically investigate the ways that options assessments were undertaken, which decision criteria were paramount, which stakeholder engagement processes were used to negotiate options, and the eventual selection, implementation and monitoring and evaluation of NBS-GI. Mangrove restoration site, coastal Kenya . Photo credit: Rob Barnes 23 ODI Report Understanding the cost-effectiveness of NBS-GI in Africa The evidence to date on effectiveness of NBSGI, and particularly urban green infrastructure, suggests that their most effective role in climaterelated DRR is to buffer against the effects of highfrequency, low-intensity events.57 Important facets of nature-based infrastructure planning, with implications for performance and effectiveness, are (1) its maintenance and (2) its dynamism over time, and particularly the response of naturebased infrastructure to climate change itself,58 all of which we explore below. The Africa chapter of the IPCC’s Sixth Assessment Report on Impacts, Adaptation and Vulnerability to Climate Change establishes with high scientific confidence that ‘Ecosystem-based adaptation can reduce climate risk while providing social, economic and environmental benefits (high confidence).’59 It notes that direct human dependence on ecosystem services in Africa is high and that resilience to the impacts of climate change may be fostered via ecosystem protection and restoration, conservation agriculture practices, sustainable land management, and integrated catchment management.60 Of particular relevance to the present report is the IPCC’s finding that the financial case has been made for ecosystem-based adaptation as a disaster risk reduction measure in urban areas of Africa: ‘Ecosystem-based adaptation can cost less than grey infrastructure in human settlements (e.g., using wetlands and mangroves as coastal protection)’.61 The present study was unable to access and identify cast-iron, detailed financial analysis to prove that ecosystem-based approaches to DRR were uncategorically more financially viable than hard-engineered infrastructure for specific risk reduction purposes. This is because the present study relied upon project documents and evaluations in the public domain. It is difficult to find in-depth comparisons of NBS-GI versus grey infrastructure feasibility studies in the publicrecord. However, when viewing infrastructure options from the broadest perspective of ‘what intervention best reduces risks and optimises overall provision of ecosystem services to society’, the multi-donor-funded C40 Cities Finance Facility has been exemplary. It has published transparently the detailed business case documentation of initiatives, including the eThekwini Municipality Transformative Riverine Management Programme, in which it has been involved as technicaladvisors. The eThekwini programme has detailed analysis showing that ‘transformative’ ecosystem-based catchment management approaches both restore vital ecosystem services to the greater municipal area and deliver best value to the taxpayer by avoiding the most damage to built infrastructure, including culvert damage, and to people’s lives (see page 26).62 24 ODI Report Effective vegetation management for healthy ecosystems also yields sustainable materials for livelihood activities, Madagascar Photo credit: UNEP 25 ODI Report 4 Nature-based green infrastructure in practice: case studies This chapter is arranged into categories of infrastructural services: DRR inland flooding, coastal flooding, landslide risk; provision of freshwater (quality and quantity); air quality; agricultural productivity; marine and coastal fisheries productivity; heat modification and cooling; shelter and green building design; and human mobility, safety and well-being in the urbanenvironment. In each category, a short rationale is provided for considering NBS-GI alone or in combination with hard engineering solutions to achieve societal goals, with supporting evidence from the literature on the merits of NBS-GI in each category. This is followed by one or more case studies associated with each category to illustrate the documented objectives, measures taken, intended and unintended outcomes, and sources of information. Where possible, information is provided of the economic instruments used to finance the programme, and analysis of the decision criteria used for prioritising green or grey-green infrastructure choices. It was difficult to obtain transparent information about options assessment or about unintended consequences in some cases. This is an important area for follow-up research. Key informant interviews helped to elaborate the ‘inside story’ in many cases. We have noted instances where information about options assessment and unintended consequences was lacking in the text. NBS-GI for riverine flood risk reduction Africa suffered $6.3 billion in flood risk damages from 2001–2018.63 Floods affect more Africans, continent-wide, than droughts, and this is due to a combination of rapid and often inadequately planned and managed urbanisation, together with more extreme rainfall.64 Green infrastructure is considered highly effective as a measure to reduce disaster risk for riverine and inland flooding.65 In this context, green infrastructure may be defined as planting and maintenance of appropriate native tree species and other vegetation. Green infrastructure activities take place in African landscapes that are often already heavily modified by human use, such as land use change, water abstraction and diversion and damming.66 Some countries have mandated the protection of riparian zones but have not yet adequately implemented these plans.67 Research to understand the land area of African cities that is permeable to rainfall and run-off, acting like a ‘sponge’ to absorb rainwater and reduce flood risk,68 calculates the ‘sponginess’ of several major cities: Cairo, 20% spongy; Durban, 40% spongy; Kigali, 43% spongy; Lagos, 39% spongy; Nairobi: 34% spongy. The ‘Africa Sponge Cities Snapshot’ is meant to inspire city planners and managers to consider whether green (vegetated) and blue (water) assets are being used as natural infrastructure to their best effect, in the context of each city’s specific exposure to changing climate hazards. 26 ODI Report CASE STUDY ETHEKWINI MUNICIPALITY (DURBAN), SOUTH AFRICA South Beach, Durban. Photo credit: South African Tourism SOUTH AFRICA DURBAN Climate change adaptation Infrastructure type Combined grey-green Sources C40 Cities Finance Facility (2021a, b), Appavoo and Moro (2020), C40 Cities Finance Facility (u.d), Friends of Ecosystem-based Adaptation - FEBA, PlanAdapt and IUCN (u.d.),69 Gajjar et al. (2021)70 Objective An ambitious initiative seeks to rehabilitate some 7,000km of waterways draining into eThekwini municipality (the greater city of Durban), which comprises the third largest urban area in South Africa and is the economic heart of KwaZulu Natal province. The municipality’s water comes almost entirely from the upper uMngeni catchment, where the deteriorating condition of ecological infrastructure is compromising the volume and quality of freshwater being supplied. According to recent studies, ‘the uMngeni catchment has lost 36% of its ability to deliver valuable watershed services, such as flood attenuation, sediment load reduction, and water quality improvement.’71 The eThekwini Municipality Transformative Riverine Management Programme combines longstanding projects to clear waste and invasive plants from the tributaries and raise environmental awareness, including the city government’s Sihlanzimvelo Stream Cleaning Programme.72 The main purpose of the intervention has been to reduce flooding in the city of Durban, and particularly in the badly affected informal settlements. In so doing, decision-makers hope to also improve the quality of water flows to themunicipality. 27 ODI Report Options assessment At assessment stage, several different riverine management scenarios were evaluated for the ecosystem services they would provide to the eThekwini Municipal Area, including surface water supply, water quality, erosion and sediment control, carbon capture and storage, food production and transport access, among others.73 The transformative ecological alternative was found to be most cost-effective in delivering across a range of disaster risk reduction (specifically, flood risk attenuation), water quantity and quality delivery and broader societal objectives. The transformative riverine management scenario foresees the extensive involvement of landowners from private and customary authorities in stream cleaning and vegetation control across the associated catchments, in addition to upscaling actions in lands controlled by the municipality itself.74 Key points of the successful business case analysis for investment in NBS-GI were: • Ecosystem services contribute approximately R4.2billion/year to Durban’s economy (US$62 million/ year at time of writing). • Ecosystem services currently supply 42% below the theoretical best case. • If left unattended, climate change will further degrade ecosystems and reduce the services derived from them by another 11% by 2040, which will have a significant impact on Durban’s economy. • Every R1 invested in a transformational river rehabilitation approach will yield R1.80–R3.40 in municipal and societal benefits. The variance in the benefits depends on the discount rate used (6% vs -1%).75 DISASTER RISK REDUCTION/ DEVELOPMENT CATEGORY Water sector: delivery of freshwater quality and flow regulation Water sector: wastewater filtering Disaster risk reduction: inland flood risk FINANCE CATEGORY $$ Bilateral and multilateral disbursements $$ National and local government budgets PUBLIC RESOURCES $$ Contributions from households, community and producers’ associations $$ Philanthropies and international NGOs PRIVATE RESOURCES Disaster risk reduction: erosion, landslide risk 28 ODI Report The strategic appraisal and options assessment phase recognised that interventions that ‘stood still’ in terms of not actively harming nature, would nonetheless lead to further degradation of ecosystem services and social and economic harms, because of the impacts of climate change. Investing proactively in river catchment rehabilitation as both a core development and a climate change adaptation measure would be the most beneficial course. The eThekwini Municipality Transformative Riverine Management Programme stands out, at present, in the African region, for the extent of economic analysis (rather than narrow financial analysis) undertaken at the options assessment phase, which explicitly valued ecosystem services across multiple societal benefit streams. The analysis looked at the wide range of social benefits possible, including green job generation and attractiveness for tourism, and avoided costs of repairing flood-related damages and treating freshwater before use.76 ‘The transformative or catchment scenario would not just avoid [climate change related] losses but would grow the ecosystem service levels beyond the present level, to offer gains relative to the status quo and promote greater resilience. This scenario represents climate risk responsive, resilience-building opportunity.’77 Business case for eThekwini Municipality Transformative Riverine Management Programme ‘Durban’s Benefit-Cost analysis to understand the social benefits of investing in nature-based solutions was fantastic, but it was a really tough piece of work to do.’78 Jessy Apavoo, UrbanShift Programme Director Measures The current plans for transformative riverine management build upon well-documented initiatives in the 18 major catchments supplying eThekwini (Durban) and include: • A clean-up of solid waste and debris before construction of the artificial wetlands, together with a public information campaign aimed at discouraging waste-dumping from informal settlements bordering the river. • Construction of artificial wetlands in sections, e.g. along the Palmiet River, to emulate the features of natural wetlands and act as biofilters, removing/trapping sediments and pollutants before entering the uMngeni riversystem. • Removal of alien plants (e.g. water hyacinth) and re-vegetation of riparian zones with indigenous plants, to stabilise the riverbanks. Outcomes – intended The current plans for transformation build upon more than a decade’s work of environmental education, engagement with diverse landowners, invasive plant clearance and stream cleaning led by the municipal authorities and various nongovernmental and civil society initiatives in the vast network of tributaries draining into the urban area. So far, researchers conclude: ‘it is clear that ecosystemand community-based approaches offer a vehicle to address multiple challenges faced within informal settlements’ in downstream areas. However, implementing the full extent of the transformative riverine management plans will be an ongoing, iterative task, involving considerable negotiation with diverse landowners and authorities and even anticipated payments by the municipality to private owners to recognise and reward the ecosystem services they provide downstream.79 29 ODI Report Outcomes – unintended Despite the investments in NBS-GI, termed ‘ecological infrastructure’ in local parlance, illegal and harmful chemical and solid waste dumping in the watershed is an ongoing issue. A citizenorganised watchdog group tracks infractions in one sub-catchment, the Palmiet River catchment, but expresses frustration at the enforcement authorities’ slowness to respond. These tensions demonstrate the complexity and high levels of ongoing regulatory enforcement and stakeholder engagement required for sustaining NBS-GI solutions and preventing ‘backsliding’ that introduces previous elements of environmental degradation. Relevant case studies in this report: FREETOWN NBS-GI for coastal flood risk reduction Marine and coastal ecosystems such as mangroves, seagrass and coral reefs provide storm protection and food security for coastal communities.83 Scientists have recently documented synergies among these coastal ecosystems, whereby the existence of seagrass meadows buffers coral reefs and atoll islands against sea level rise by producing more sand.84 As well as providing these significant climate change adaptation, development and DRR benefits, mangroves and seagrass are some of the most carbon-rich habitats known to science and thus their protection and restoration as carbon stores makes a significant contribution to climate change mitigation.85 One challenge with coral reef protection as a DRR measure is that reefs are highly at-risk of dieoff from warmer, more acidic ocean waters. As greenhouse gas concentrations in the atmosphere increase and global warming continues, so the window of opportunity is closing for reefs’ viability as a nature-based solution.86 Nonetheless, at present, there is still important potential to use a combination of coastal ecosystem and restoration measures, including for mangrove, seagrass and coral reef ecosystems, to reduce risks of storm surge and/or sea level rise. In Africa, these climate change impacts particularly affect lowlying, heavily populated areas in the Western Indian Ocean: from Mozambique to Somalia, and along the coastlines of the Gulf of Guinea, Gambia, GuineaBissau and Sierra Leone in West Africa; the potential for NBS-GI is also strong in these regions.87 Relevant case studies in this report: SOUTHWEST MADAGASCAR NBS-GI for landslide risk reduction Landslides are among the hazards most often addressed by projects with nature-based solutions by the World Bank’s Global Facility for Disaster RiskReduction.80 In West Africa, landslides are identified as having caused human suffering and damaged vast resources; and a major initiative called ‘Capacity building and the impact of climate-driven changes on regional landslide distribution, frequency and scale of catastrophe’ investigated the drivers of landslides. It concluded that landslides occur during the rainy season as a result of intense rainfall, and projected that periods of more intensive rainfall under climate change will worsen the risks.81 Nevertheless, a more recent assessment of landslide risk across Niger and Senegal in West Africa and Ethiopia, Kenya and Uganda in East Africa found that the country-level landslide risks are even greater in the focal East African countries, due to their mountainous terrain, seismicity and the exposure of large populations to landslide hazards as a result of rapid urbanisation and population growth.82 30 ODI Report Cross-cutting: adaptation and mitigation Infrastructure type Green [Blue] Sources Blue Ventures and Velondriake Association (2020), Evans (2018a), Jones (2018)89 Objective Dominant development objectives in this local area are to protect coastal ecosystems, including shore stabilisation, storm protection, coastal flood risk reduction, and enhancement of local marineand coastal-based livelihoods such as fisheries and seaweed farming. Mangrove conservation and restoration can contribute to coastal flood risk reduction and also to fisheries productivity, as healthy mangrove ecosystems provide nursing and breeding grounds for many species. In the project area, and indeed, more broadly along Madagascar’s west coast,90 efforts have been underway to reverse mangrove forest degradation, and hence replace the green infrastructure being lost. Mangroves are among the ‘most carbon-dense of any forest type, with carbon stocks meeting or exceeding those of their terrestrial peers – temperate, tropical and boreal’.91 Madagascar is home to 2% of the world’s mangrove ecosystems.92 More than 20% has been removed as a result of charcoal production, timber extraction and development.93 Higher, more mature trees have been removed in many areas, leaving smaller plants and sparsercoverage. The community organisation Velondriake Association has linked with Blue Ventures and Plan Vivo. Through this partnership, the organisations have sought to document, verify and market the CASE STUDY VELONDRIAKE MARINE PROTECTED AREA, SOUTHWEST MADAGASCAR88 Tahiry Honko project: community-led mangrove management, Helodrano Fagnemotse (Bay of Assassins) HELODRANO FAGNEMOTSE Coastal Madagascar. Photo credit: UNEP MADAGASCAR 31 ODI Report carbon values of healthy mangrove forest through the market in voluntary carbon credits. This makes it a fully cross-cutting project, with climate change mitigation, adaptation and disaster risk reduction objectives. Options assessment A first, concerted effort by Velondriake Association and Blue Ventures to halt and reverse mangrove degradation was motivated by DRR and sustainable livelihoods purposes. The organisations explored practical ways that they could incentivise and enable mangrove restoration. Once restoration activities were underway with Blue Ventures grant funding, the organisations identified the option to connect with the Plan Vivo Foundation to sell carbon credits (the project area under the carbon credit scheme being a part of the larger operational area). The partners saw this as a way of financing the protection and maintenance of this green infrastructure more sustainably, for the long term. Measures Ecosystem protection and restoration activities involve: • strict conservation of existing mangroves • prevention of ecosystem conversion • improved land use management (these all overseen by village management committees) • mangrove forest monitoring, patrolling, data collection (undertaken by an appointed monitoring and evaluation team). Disaster risk reduction: coastal flood risk DISASTER RISK REDUCTION/ DEVELOPMENT CATEGORY $$ Bilateral and multilateral disbursements PUBLIC RESOURCES $$ Carbon credit sales (voluntary market) PRIVATE RESOURCES FINANCE CATEGORY Marine and coastal fisheries productivity 32 ODI Report The community members are not directly paid for mangrove planting but are provided with meals when they undertake the activities. The funds generated are programmed into community development activities as describedhere. Alternative terrestrial tree species have been planted near to the villages involved in the project, to provide fuelwood and building materials for the community members and so give them an alternative source of wood to the mangrove forests.94 The project has, further, supported training in alternative livelihoods for community members: • work in the tree nursery • training in beekeeping in three of the project villages (Befandefa, Ankindranoke and Andalambezo), which is expected to reinforce the value of intact mangrove forests as a source of nectar for bees • support for sea cucumber farming and seaweed farming: sea cucumber farming requires seagrass reserves to sustain it, which further has a beneficial impact on the local environment.95 Mangrove restoration projects, like other NBS-GI interventions, highlight the importance of gender dynamics and of empowering women in management decisions. Mangrove restoration export Salomao Beira noted (with general reference to the African region): ‘In many African societies, a lot of the livelihood activities are done by women. But sometimes they are not involved in restoration work from the start: I know there have been examples where the men have a meeting first, and then they bring women in. I think if you want to do restoration and community engagement in the best possible way, you cannot just rely on ecologists. You need to bring in some of these social researchers, or anthropologists, who can communicate really well and help build that confidence for women to participate … I think women are already there in the restoration work, but there’s a great potential to have more success by engaging with them evenfurther.’96 Financing has been via UK government grants and sells of carbon credits via Plan Vivo. The disbursement of the funding is aligned with Madagascar’s national regulations. The Stratégie Nationale REDD+ Madagascar was enacted by the Government of Madagascar in May 2018. This policy requires all carbon sale agreements to be signed by the Bureau National Coordination-REDD+ (BNC-REDD+), and the revenue to be deposited in a REDD+ fund managed by that national government agency, which retains a 22% share of revenues centrally, along with a further 5% of revenues to be ringfenced for the ‘National REDD+ risk buffer’.97 Community projects then submit budgeted implementation plans to request their share of revenue from the REDD+ fund. Around 50% of the carbon revenue sales are channelled from the Tahiry Hoko project directly to community activities, to fund communities’ natural resource management and local development activities;98 the balance of funds goes (in addition to national government) to the manager of the protected area (Velondriake Association) and a small portion for the management of the carbon sales: accounting, reporting and validation activities, etc.99 39 ODI Report Agricultural productivity was increased where the water harvesting and the environmentally-friendly, water spreading weir techniques were used with community participation. According to the Mid Term Review, sorghum yields doubled on many of the farms that have benefitted from improved water harvesting. Most farmers surveyed in a random sample of 200 households across the project area have reported a general increase in production from below 10% to as much as 70% - thanks to the project.116 Groundwater was previously overdrawn, generating community tensions over water scarcity: groundwater recharge has now significantly improved as a result of the combined green-grey infrastructure measures.117 In several villages, the project’s rollout of sustainable irrigation was explicitly connected with improved food security outcomes. Where previously, farmers were dependent on rainfed agriculture, the irrigation system, associated with integrated water management, enabled farmers to produce outside of the normal rainy season. According to Practical Action, ‘an estimated 4,500 households benefitted from the three water harvesting structures constructed ... 54% of these households reported an increase in crop yields of 50% or more as a result of improved access to water on their farms along the wadi.’118 ‘The project won the 2017 Land for Life award for improving food security and disaster resilience and reducing community tensions through sustainable management of dryland areas of North Dafur.’ UNEP 119 Outcomes – unintended In such a fragile environment with many demographic movements and exposure to climate hazards, it was not – at first – certain whether the project would ‘succeed’ per se. The funders and programme managers were, however, encouraged by the progress made in the first phase, which showed that sustainable development approaches are possible even in essentially a ‘humanitarian relief’ context. Furthermore, the funders note: ‘government as well as communities have shown that they are willing and able to contribute to natural resource management. This is demonstrated by the significant traction that the IWRM [integrated water resources management] model has gained at state level among government and communities. A Catchment Management Forum with political support from the state government was established and now provides a platform for dialogue across stakeholder groups to improve natural resource management. A vision, constitution and programme of action were also developed in a participatory manner by the members of the Forum.’ 120 Despite the achievements of the first phase, several key gaps came to light. These are flagged for concerted attention during the project’s second phase,121 namely: • In the first phase, important foundations for data collection were established, with the installation of meteorological stations in the project area. However, better environmental (especially hydrological) monitoring, generating more data points, is needed. • This is essential to inform robust participatory decision-making processes. • Avenues should be explored for communitybased approaches to data collection, given that programme managers and scientists based in the provincial capital face transport and access issues to the project sites. 40 ODI Report NBS-GI for air quality including localised PM2.5 and PM10 mitigation Increased urbanisation, industrialisation, motorisation and the emission of mineral dust from deserts have combined to increase outdoor pollution across Africa; much particulate matter, especially mineral dust, is transported across national borders before it is deposited.122 Forest fires, vehicles, domestic fires and industrial emissions are particularly implicated as direct human sources of air pollution. These emissions take a heavy toll on human health, and other facets of economic and human development, especially in Africa’s high-density urban areas such as slums.123 In the world as a whole, exposure to all types of particulate pollution is three times greater in lowand middle-income countries than in high-income countries.124 The European Union-funded iSCAPE project has researched the implementation of NBS-GI solutions in European cities as a means of reducing particulate pollution. The project showed that the installation of hedgerows and trees, if ‘correctly positioned’ in urban areas, can reduce ambient particulate matter by 50%.125 It is possible that similar results could be achieved in African locations, but this needs to be piloted and sufficiently researched. Mapping of fine particulate matter (PM2.5 and higher) shows very high concentrations in the Sahara and north Africa region – reflecting the incidence of desert dust.126 Agroecological and agroforestry methods are among the chief ways of tackling land degradation in the Sahel, where such measures are feasible and may help to reduce dust emissions (see ‘soil fertility’ below). The WHO has indicated that urban greening and street cleaning can remove dust and reduce the potentially harmful, compounding effects of localised pollution and desert dust. Relevant case studies in this report: DAR ES SALAAM FREETOWN NBS-GI for agricultural productivity, including soil fertility Land-based ecosystems, the climate, and climate change are intricately connected. As described in a synthesis of the IPCC’s Special Report on Climate Change and Land,127 climate change is expected to alter: • the distribution of land cover • biodiversity and the mix of plant and animal species in ecosystems • vegetation structure and productivity and • nutrient and water cycles. At the same time, land plays an important role in the climate system. The physical, ecological and hydrological conditions of land all influence its interaction with the atmosphere. As well as the composition of rocks and soils, extent of water, ice and type of vegetation cover in ecosystems in natural or semi-natural states, the human alterations to land uses also affect fluxes of greenhouse gases in the atmosphere, and the heating or cooling qualities of the land surface. The land conditions that influence the climate can be a result of direct human management and use; for example, deforestation, afforestation, urbanisation, irrigated agriculture and land state (i.e. degree of wetness, degree of greening, amount of snow, amount of permafrost).128 41 ODI Report At present, land is a source of greenhouse gas emissions into the atmosphere, contributing to human-made climate change. It does not have to be this way. Agriculture, forestry and other types of land use account for 23% of human greenhouse gas emissions. Meanwhile, natural land processes absorb carbon dioxide equivalent to almost a third of carbon dioxide emissions from fossil fuels and industry globally.129 In this context, integrating climate-smart measures in agriculture that contribute to both adapting to climate change and mitigating against climate change is imperative. There is a lack of consensus as to whether nurturing soil health qualifies as a ‘nature-based solution’ under the IUCN guidelines. However, experts in the UK, in Asia and in Africa have argued that restoring soil health through agroecological means is a quintessential NBS-GI approach. Many consider that ‘nature-based farming’, relying on organic methods, is a valid framing and approach, which contrasts with man-made, chemical inputs. Mrunalini et al. (2022) note that healthy soil, although prone to degradation by ‘conventional agricultural practices’ nevertheless ‘delivers several ecosystem services along with its control on microbial activity, nutrient recycling, and decomposition’. In this context, specific NBS-GI can contribute to restoring soil quality and so to improving agricultural productivity.130 Mrunalini et al. (2022: 1) describe specific nature-based solutions as follows: ‘Indigenous practices such as sheep penning, tank silt application [both of which involve the capture of effluents from livestock to use as organic manure], green manuring [including green manure crops into crop rotations, such as Sesbania speciosa and Gliricidia maculate] and refuse from croplands and households have the potential to restore and maintain soil fertility. Biofertilisers can add nutrients (nitrogen (N) fixers), fix up to 300 kg of nitrogen per hectare through biological nitrogen fixation and nutrient availability in the soil. Biochar, a commonly used product, can increase soil moisture availability by 8%–10% and aids in mitigating climate change through carbon sequestration. … Biogas slurry, the effluent from biogas reactors, contains various nutrient elements that can enrich soil fertility. The holistic approach in a farming system, through integration of different enterprises, reduces dependence on off-farm resources. Soil management through naturebased options will maintain crop productivity and sustainability in the long run without any adverse effects on the environment.’ RECSOIL, the recarbonisation of global soils initiative, is perhaps indicative of this movement. It is a global partnership facilitated by the Food and Agriculture Organisation of the United Nations, providing: ‘a mechanism for scaling up sustainable soil management (SSM) with a focus on soil organic carbon (SOC). The priorities are to: a) prevent future SOC losses and increase SOC stocks; b) improve farmers’ incomes; and c) contribute to food security.’131 Further methods for nurturing ecological functions on agricultural and agroforestry land include, for example, specific micro-habitat features such as preserving semi natural ecosystem features within farmed landscapes or taking specific measures in the managed, crop production areas to support pollinators (e.g. see the example of placing cut branches strategically around plots, to support pollinator breeding in Ghana’s cocoa forest landscape.132 42 ODI Report A range of conservation agriculture and agroecological approaches use organic inputs and agricultural techniques that seek to enhance the complexity and range of ecosystem functions on farmed land and agroforestry landscapes, for the purposes of: • sustaining agricultural productivity over time • supporting diversification and hence resiliency of farming and agroforestry systems and related rural livelihoods. In African contexts, initiatives to boost agricultural productivity and enhance natural ecosystem functions including soil fertility are frequently pursued in a context of neutralising or reversing land degradation. The United Nations Convention to Combat Desertification (UNCCD)’s Land Degradation Neutrality Target has 120 government signatories, including most African nations. African governments have also stepped up to commit to specific land restoration efforts.133 A science-policy assessment of land degradation neutrality programmes concluded that stakeholders championing the reversal of land degradation have high hopes that their interventions will yield multiple well-being and livelihood benefits.134 However, the extent to which they do so depends on ‘contextual’ factors: ‘Achieving land degradation neutrality requires an enabling environment: appropriate and inclusive policies and regulations, sustainable institutions, access to finance, and an effective science-policy interface.’135 An outstanding success story, that of Farmer Managed Natural Regeneration in Niger, counts among its ‘ingredients of success’ the replicability of its technique (transference of local knowledge) and relative low cost.136 Farmer Managed Natural Regeneration is a practice based on indigenous knowledge. It is a method of pruning and cutting trees so that they vigorously regrow and produce more food, fuelwood and fodder sustainably for communities’ use, without the need for frequent, costly replanting. The management technique allows for ‘increased water infiltration and retention, a reduction in wind speed, a reduction in local temperatures due to dispersed shading, and additional organic matter from leaf fall and litter, as compared to when trees are cut down altogether’137 and contributes to improving soil fertility and land productivity. Work by farmerchampions, scientists and extension workers together with traditional leaders has enabled the practice to spread by word of mouth and lead to millions of hectares of land degradation reversal in Niger – at a scale that is well beyond plot level and qualifies as landscape-level green infrastructure by any definition. This report does not aim to cover in detail the vast topic of conservation agriculture and agroecological approaches in Africa, nor the divisions and disagreements among proponents of conservation agriculture and agroecology as to which are genuinely ecologically robust and sustainable. Here we simply note that a great diversity of community-based organisations and networks as well as domestic and international NGOs and research institutions are aiming to enhance the ecological function of farmed land in ways that are adaptive to climate change, sequester or avoid the emissions of greenhouse gases and offer sustained productivity. We also note the considerable criticism by civil society groups of the lobbying activity by international agribusiness in climate change policy fora – agribusinesses that are accused of promoting agricultural chemicals derived from fossil fuels and contributing to emissions.138 43 ODI Report Relevant case studies in this report: DARFUR NBS-GI for marine and coastal fisheries productivity A thriving fisheries sector, which relies on wellmanaged coastal ecosystems, is an acknowledged priority for African countries. The African Union’s blueprint for African development, Agenda 2063, highlights a robust, well-managed blue economy as a pillar of the continent’s growth and development. Among the transformational outcomes sought under the Agenda is that ‘the beginnings of value addition blue economy – fisheries, eco-friendly coastal tourism, marine biotechnology products and port operations – will emerge’139 Natural capital – the stocks and flows of ecosystem services provided by nature – is fundamental to fisheries productivity but has been under direct duress from ecosystem/habitat destruction as well as indirect harms from climate change. The African Ministerial Conference on the Environment statement points the finger at ‘weak governance infrastructure and lack of sustainable management of institutional frameworks [which] has contributed to, inter alia, the degradation and depletion of marine and coastal ecosystems, maritime insecurity and illegal, unregulated and unreported fishing, thereby affecting national economies.’140 Meanwhile, global warming has undermined coastal and marine ecosystems in several ways. Ocean waters themselves have warmed at unprecedented rates, shifting the climate envelope of many species. At the same time, there is reduced dissolved oxygen in upper layers of ocean waters (deoxygenation) plus, the oceans have taken up much of the increased carbon dioxide in the atmosphere, leading to acidification of ocean waters. As a result of these changes, many marine species around Africa’s coasts have changed in abundance and distribution. Coral reefs are at very high risk of loss and damage, even at current levels of global warming.141 Relevant case studies in this report: GAZI BAY PRASLIN ISLAND 44 ODI Report Cross-cutting: adaptation and mitigation Infrastructure type Green Sources ESPA (2018), IPCC (2019), Hou-Jones et al. (2021), Omar (2022).142 Objectives Mangroves are critical assets for villages such as Gazi, on Kenya’s Indian Ocean coast. They act as a nursery ground for fish, and as a critical form of natural infrastructure to protect the coastline from erosion and storm damage. The mangroves have traditionally been a source of wood for fuel and building but have increasingly been under pressure of unsustainable use. The Mikoko Pamoja (‘Mangroves together’ in Swahili) project aims to both prevent further deforestation of mangroves in the area and also to restore mangrove forest. Associated objectives include: storm surge management; sediment trapping; fisheries productivity in the coastal ecosystem. Noninfrastructure benefits: income from seaweed farming; promotion of gender equality. Inland afforestation is aimed at reducing soil erosion further up the catchment. Options assessment Mikoko Pamoja became the world’s first ‘blue carbon’ project in 2010, meaning that the local community group, in collaboration with international and domestic researchers, quantified the carbon captured by intact mangroves (including the immense amount captured in the root systems and surrounding silts). CASE STUDY GAZI BAY, KENYA KENYA GAZI BAY Recently planted mangroves, Kenya. Photo credit: Rob Barnes 45 ODI Report Disaster risk reduction: coastal flood risk Disaster risk reduction: erosion, landslide risk Marine and coastal fisheries productivity $$ Bilateral and multilateral disbursements $$ National and local government budgets PUBLIC RESOURCES $$ Contributions from households, community and producers’ associations $$ Carbon credit sales (voluntary market) PRIVATE RESOURCES Agricultural land productivity DISASTER RISK REDUCTION/ DEVELOPMENT CATEGORY FINANCE CATEGORY It was the measurement of the carbon in the intact mangroves which highlighted the financial attractiveness of mangrove conservation – with its multiple functions and societal benefits. The scientifically founded carbon measurement unlocked a sustainable financing pathway: the community and research partners together worked with the Plan Vivo Foundation to quantify the carbon value of conserved and restored mangrove forest and generate carbon credits for sale on the international market. The revenue stream from the carbon credit sales has been managed by a multistakeholder committee, for the benefit of the community, by spending on various local development projects (health, education, etc.) Measures Mangrove conservation and restoration have been undertaken to protect the coastlines from coastal flooding, storm surges and erosion. Inland, in the upstream communities, tree replanting is contributing to reducing the risk of soil erosion. Furthermore, the mangrove regeneration makes new forms of sustainable livelihood activities – such as beekeeping – possible. Financing and public/private sector involvement The initial work of carbon measurement relied heavily on grant funding from international public sources (e.g. Government of the United Kingdom143). This was used to scope the feasibility of carbon market entry for a more sustained, long-term revenue source facilitated by the Plan Vivo Foundation and its marketing platform. 46 ODI Report Revenues from sale of carbon credits are deposited in a community development fund. Outcomes – intended • 117.4 hectares of mangrove forest area conserved and restored • 1,081 households benefitting directly from the sale of carbon credits • US$118,000 in carbon revenue sales generated in total (2010–2021).144 Outcomes – unintended • The community development fund enabled by the scheme was able to provide food packages to particularly vulnerable individuals and households (e.g. widows) during the COVID-19 pandemic – demonstrating a contribution to community resilience that was entirely unforeseen. • Now the Mikoko Pamoja mangrove project stakeholders are interested to merge their initiative with a seagrass conservation initiative as part of a broader marine payment for ecosystem services scheme. • Furthermore, the success of their scheme has generated interest from other communities in coastal Kenya and Tanzania on the feasibility of developing similar blue carbon schemes in their localities. Already, the Gazi Bay pilot was replicated in Vanga Blue Forest, another coastal stretch in Kenya; and the Kenya Marine and Fisheries Research Institute has accessed European Union funds to enable the approach to be extended to the significant mangrove reserves at Lamu, Kenya. • Parliamentarians from Kenya, Mozambique and Tanzania have visited and studied the mechanics of the Mikoko Pamoja project, with a view to understanding how legislation could and should be used to protect mangroves.145 A leader of a section of the mangrove protection and restoration area at Gazi Bay, Kenya. Photo credit: Rob Barnes 47 ODI Report A leader of a section of the mangrove protection and restoration area at Gazi Bay, Kenya. Photo credit: Rob Barnes 48 ODI Report SEYCHELLES PRASLIN ISLAND Seedlings, Seychelles. Photo credit: TRASS Cross-cutting: adaptation and mitigation Land – erosion reduction Infrastructure type Green The Seychelles case study investigates the achievements, challenges and financing flows into nature-based solutions in two parts. The first part explores the debt-for-nature financing element of ecosystem restoration in Seychelles: documenting the mechanism by which the debt swap occurred and describing briefly how the funds for nature are managed. This is a ‘top down’ account of how the money flows. The second part of the case study explores communityand ecosystem-level development challenges, and how one non-governmental organisation, the Terrestrial Restoration Action Society of Seychelles (TRASS) has gone about mobilising a range of funds to meet local needs. This is a ‘bottom up’ account of how environmental degradation has been perceived and funds raised for specific activities at local level. 1. The Seychelles debt-for-nature swap Source Government of Seychelles – Ministry of Finance (2016), Seychelles Conservation and Climate Adaptation Trust (SeyCCAT); Pouponneau (2020); Patel et al. (2021)146 Objective To finance critical coastal-marine infrastructure and sustainable island livelihoods, funded by a debt-for-nature swap instrument. CASE STUDY PRASLIN ISLAND RESTORATION, SEYCHELLES 55 ODI Report As well as the flood attenuation benefits described earlier, the preservation, creation and maintenance of green spaces can, through shade cover, provide significant passive cooling benefits and reduce the urban heat island effect.173 A study in Nairobi, Kenya demonstrated not only the difference in people’s ‘thermal comfort’ between tree-shaded and non-shaded areas of the city. It also demonstrated that particular tree species (i.e. with denser canopy structures) are optimally effective in cooling ambient temperatures and enhancing human thermal comfort.174 This accords with the observation by Cook et al. that ‘different species and varieties of trees differ in the extent to which they provide shade, reduce particulate and other pollution, and buffer noise, humidity and temperature. Therefore, a diverse tree community fulfils more of these functions. Higher habitat diversity provides even greater benefits on city cooling than does the presence of greenspace alone.’175 Planting and green space not only contributes to carbon capture but also reduces greenhouse gas emissions indirectly by reducing the need for powered cooling services, for example air conditioning.176 In buildings, a range of good practice methods are viewed, in combination, as being effective in promoting passive cooling and so safeguarding human health and reducing the need for powered cooling services. Good practice measures combine both architectural aspects – which are inherently of the built environment, such as natural ventilation, window shades and white walls – together with NBS-GI such as green roofs.177 Relevant case studies in this report: DAR ES SALAAM FREETOWN Restoration area, Seychelles. Photo credit: TRASS 56 ODI Report TANZANIA Schoolchildren enjoy green space in Dar es Salaam. Photo credit: World Bank DAR ES SALAAM CASE STUDY DAR ES SALAAM, TANZANIA Msimbazi Opportunity Plan: Transforming the Msimbazi Basin into a Beacon of Urban Resilience178 Cross-cutting: adaptation and mitigation Source World Bank u.d.(a), World Bank (2022), Government of Tanzania (2020), Government of Tanzania (2018)179 Objective Dar es Salaam is one of Africa’s fastest-growing cities and is on a pathway to megacity status. It also faces dangerous flood risks. Over the years, changes in the Msimbazi river basin have materially changed the morphology of the river and its ecosystem functions, which run through the city. Deforestation in the upper basin has increased erosion and sedimentation of the river, resulting in large sediments downstream which have – among other things – made the river shallower as it flows through the city. Uncontrolled urbanisation has decreased the permeability of ground in the river basin and increased runoff. Climate change has amplified these problems: when it rains intensively, the shallower river cannot hold the excess water and flooding – including rapid onset flash flooding – affects a large portion of the urban area. This includes areas where people have built homes and small businesses illegally in the flood plain. Sadly, during the most severe floods in December 2011, more than 10,000 people were displaced from their homes and 42 people killed. Furthermore, urbanisation has created an urban heat island and temperatures are searing. In response to these risks, the national government, in collaboration with diverse local stakeholders, has conceived the Msimbazi Opportunity Plan , totalling more than 40 activities in four strategic phases. The principal objectives of the plan: to manage urban riverine flood risk, urban heat risk, human well-being, safety andmobility. 57 ODI Report Disaster risk reduction: inland flood risk Cooling services, heat modification Human mobility, safety and well-being in the urban environment $$ Bilateral and multilateral disbursements $$ National and local government budgets PUBLIC RESOURCES $$ Philanthropies and international NGOs PRIVATE RESOURCES Options assessment There have been a number of historic initiatives to explore and test green infrastructure in Dar es Salaam, building up to the current, internationally funded, multimillion-dollar, multi-pronged effort. In 2017, Dar es Salaam City Council formed a working group with five municipal councils, regional government, local universities, relevant nongovernmental organisations, and local experts and a small facilitating team, consisting of ICLEI and UFZ to investigate the potential for urban greening to address deteriorating quality of life in the city.180 Partners contributed data and experience toward production of a Thematic Atlas which mapped natural assets in the city such as green space, overlaid with problem areas where urban heat islands and areas of poor air quality were particularly acute.181 The working group used the concept of NBS-GI to address the heat and air quality challenges, devising a range of localised demonstration projects. This provided the foundations for a more ambitious process to follow in 2018. The process was also founded on a history of contentious efforts by governmental authorities to remove informal settlers from the highest flood risk areas. These historic efforts had met with social opposition, and highlighted the need for a new, negotiated approach.182 DISASTER RISK REDUCTION/ DEVELOPMENT CATEGORY FINANCE CATEGORY 58 ODI Report A concerted multistakeholder participatory process was undertaken in 2018 with several stages: to define the scope of the problem – based on a mixture of scientific data and analysis and local knowledge – and to chart a range of actions to reduce deaths, injuries and disaster losses and also improve the quality of life of urban residents. This was dubbed a process of ‘design charettes’ after the French word charettes, signifying ‘a participatory planning process in which representatives from all stakeholder groups including community members, national and local Government, knowledge and education centres, industries, and the relevant professional service organization are assembled in one stakeholder team and are given the task and mandate to design the best possible solutions for a complex problem that affects them all. The stakeholders commit themselves and/or their organizations to the actions designed as part of the solution.’183 Over the course of several months in 2018, more than 150 individuals from 59 institutions took part in 8 stakeholder workshops and 49 meetings. They collected information to be able to assess the scope of environmental degradation and flood risk. Collectively, they devised the Msimbazi Opportunity Plan. The plan has the ambition to transform the Msimbazi Basin in Dar es Salaam into ‘a beacon of urban resilience.’184 Economic analysis Dar es Salaam provides an especially useful case study because an economic costing of the returns on investment of green urban development measures was undertaken by Anchor consultants and The Nature Conservancy for the World Bank. This extensive document provides a far more detailed biophysical appraisal and costing of a range of NBS-GI intervention scenarios than is typically available for African project locations; and it also accounts for the costs of resettling at-risk groups from the flood plain.185 Turpie et al. (2016) explain that the protection, restoration and/or enhancement of natural systems were selected as ‘among the most feasible options’ for addressing Dar es Salaam’s mounting flood-related losses. They add: ‘There are substantial areas of degraded forest in the catchment that could be restored, and floodplains lower in the catchment have been artificially disconnected from the river, greatly reducing their potential for flood mitigation and co-benefits.’ They set out a range of five scenarios for the deployment of green infrastructure which reduce flood risk and/or reduce people’s exposure to flooding, as shown in the following tables. 59 ODI Report 1 GUD: (a) restoration of forests in upper catchment, (b) rehabilitated and enhanced riparian and floodplain areas in middle catchment, (d) river cleaning in middle catchment, (c) floodplain rehabiliation in lower catchment, (e) swales in flood prone areas. 2 This is less than the sum of 1 and 2 since the number of buildings at risk in the buffer is reduced, and so a reduced number of households need to be resettled. Key: EAL: Expected Annual Losses GUD: Green Urban Development Source: Turpie et al.186 (reproduced under Creative Commons licence 3.0) The analysis demonstrated that without interventions in the catchment to either remove people and structures from the most flood-prone areas (reduce exposure) or reduce flood risk in flood-prone areas, the estimated annual losses (shown as ‘baseline’) would be $47.3 million. Each of the scenarios for ‘green’ intervention above shows the reduction in estimated annual losses that would be achieved. They concluded that: ‘Costs generally increased from Scenario 1 to5. Nevertheless, all the options considered had positive outcomes, with the time taken for the return on investment to exceed 1 ranging from 7 to 19 years’.187 Scenarios 1-5 and their estimated costs Reduce exposure No interventions in flood prone areas People and structures removed from 60m buffer in flood prone areas Reduce flood risk No interventions in catchment Scenario 1 $62.6 million GUD interventions in catchment1Scenario 2 $84 million Scenario 3 $138.5 million2 GUD with additional storage Scenario 4 $124 million Scenario 5 $178.5 million Impacts of Scenarios 1 to 5 on expected annual losses (EAL), and the percentage change in EAL Reduce exposure No interventions in flood prone areas People and structures removed from 60m buffer in flood prone areas Reduce flood risk No interventions in catchment Baseline US$47.30 million Scenario 1 US$37.24 million (-21%) GUD interventions in catchment1Scenario 2 US$28.87 million (-39%) Scenario 3 US$23.16 million (-51%) GUD with additional storage Scenario 4 US$27.78 million (-41%) Scenario 5 US$21.64 million (-54%) 60 ODI Report Measures A large proportion of the solutions subsequently adopted are NBS-GI; they can be summarised as: Intervention: proposed or underway Green/grey character of intervention Primary purposes of interventions Reforestation of upper and middle catchments Green Reduce erosion and sedimentation Improve water retention of upper and middle catchments; capture carbon and so contribute to climate change mitigation Re-zoning of highest flood risk area in city centre into parkland and creation of new park Green Absorb flood waters in the city itself Create a ‘cool corridor’ in the middle of the city, mitigating the urban heat island Create recreational value for people in the city centre Improve functioning of the Bus Rapid Transit system in the city, which is otherwise disrupted by frequent flooding Governance measures: improved land use planning and enforcement including planned relocation of households with compensation Cross-cutting Remove people and assets from high flood risk area Dredging, engineering works to remove accumulated sediment that is contributing to flooding in river channel Grey/cross-cutting Deepen river channel to reduce risk of overspill in event of rainfall and higher water volumes The combination of measures is intended to transform the riverine areas of the city from a hazardous area to a ‘green heart and lungs of thecity’. Financing and public/private sector involvement The first round of mapping and consultation, culminating in 2017, and obtaining the backing of the President’s Office, attracted $330 million in World Bank funding. The second round of charettes mobilised a further World Bank grant and loan package. The World Bank is now providing a further $200 million in concessional finance through the International Development Association to support implementation of the measures (announced October 2022).188 These consultative processes and core funding have also galvanised civil society organisation initiatives – for example, a city-wide voluntary treeplanting initiative involving local school children. 61 ODI Report Outcomes – intended This case study underlines the importance of thorough, consultative and stepwise processes to establish sound data and stakeholder interests, with each step building on the last.189 Earlier multistakeholder mapping exercises provided data and analytical foundations, as well as strengthened working relationships among interest groups, to define the complex drivers of poor human development and climate vulnerability in Dar es Salaam. These early convening and mapping processes, first under the aegis of the Thematic Atlas compilation and later as part of the ‘Design Charettes’ helped identify a package of measures to implement and attracted external funding. Aerial view of mangrove swamp area In Dar es Salaam City. Photo credit: istockphoto 62 ODI Report Freetown. Photo credit: Slum Dwellers International SIERRA LEONE FREETOWN Adaptation and mitigation Infrastructure type Green(as part of a larger city plan incorporating both grey and green components) Sources Freetown City Council (2019); Freetown City Council (2022a); Toya et al (2021), Eric Hubbard (author); GFDRR (2021)190 Objective Freetown is located at the seaward tip of a heavily forested, mountainous peninsula in western Sierra Leone, dominating its urban, socio-economic and natural landscape. Over the past 50 years, Freetown’s population increased nearly 10-fold while natural forest cover declined by about 70%. Hence, from 2011 to 2018, 12% of the total tree cover in the area was lost each year. Thisthreatens natural ecosystems and exacerbates risks of landslides, flooding, coastal erosion and biodiversity loss, while causing endemic water shortages. Against this backdrop of expanding climate risk and vulnerability, Mayor Yvonne Aki-Sawyer and the Freetown City Council through the Transform Freetown Agenda (5-year city development plan) codesigned with climate vulnerable communities the #FreetownTheTreeTownCampaign to plant, grow and digitally verify one million trees by 2023. The aim is to increase the city’s tree and vegetation cover by 50%, linked to a natural capital investment strategy to ensure sustainable financing for climate resilient ecological infrastructure to manage climate risk and increase adaptive capacity in the most climate vulnerable spaces: targeting the 74 informal settlements across the city. CASE STUDY FREETOWN, SIERRA LEONE 63 ODI Report Cooling services, heat modification Particulate matter and air quality improvement Disaster risk reduction: erosion, landslide risk $$ Bilateral and multilateral disbursements $$ National and local government budgets PUBLIC RESOURCES $$ Contributions from households, community and producers’ associations $$ Impact investment tokens $$ Philanthropies and international NGOs PRIVATE RESOURCES The tree planting and growing programme is communitybased with the intention of creating jobs, including in local tree nurseries from where seedlings are sourced, and aiming to create a sustained revenue stream by marketing tokens to impact investors through a tree investment platform with Greenstand. Specific outcomes targeted by the tree growing initiative are: • Enhanced environmental quality and resilience in the city including through the cooling effect of tree cover, which counteracts the urban heat island effect. • A contribution to climate change resilience and disaster risk reduction, especially from floods and landslides, through slope stabilisation and restoration of coastal mangroves. ‘The research that has gone into planning Transform Freetown is unique in Sierra Leone. The scale of it allowed for more inclusion and more participation than anything we have done before. We drew together data from a needs assessment conducted at zonal level, as well as direct observation of service provision, and interviews with service providers. It has set a benchmark for work in this field in Sierra Leone and we are already considering how we can build on it.’ Abdul Karim Marah – Development Planning Officer, Freetown City Council191 DISASTER RISK REDUCTION/ DEVELOPMENT CATEGORY FINANCE CATEGORY 64 ODI Report Options assessment The ‘Transform Freetown’ plan calls the city an ‘environmental timebomb’ due to unfettered deforestation.192 This lack of, or seriously degraded, environmental infrastructure that was highlighted by Freetown residents (including informal settlement residents), business owners and workers through extensive consultations in 2018, which led to the ‘Transform Freetown’ plan.193 The #FreetownTheTreeTown initiative is a critical component of the plan. In August 2018, a comprehensive needs assessment was undertaken to capture residents’ views of service delivery.194 It involved 310 meetings at zone level with ward committee members, councillors, youth groups, religious groups, women’s groups, and other community stakeholders, facilitated by 500 trained facilitators, including members of the Federation of Urban and Rural Poor. Later, the data from the zone meetings was reviewed and validated via further meetings with Ward Development Committees in each of Freetown’s 48 wards. The city council then formed multi-stakeholder working groups comprising councillors, city council staff, representatives from the national government, NGOs, development partners, community representatives, members of the public, and members of the private sector were formed for each priority sector. In total, 399 stakeholders were involved, from the introductory meeting all the way through to validation of findings and recommendations. The city plan states: ‘Their expertise is helping clarify the issues and develop the solutions that will enable Freetown City Council to deliver the Transform Freetown agenda.’ Measures The Treetown initiative has developed an integrated tree seedling purchasing, distribution, planting and growing system involving communitybased organisations. The programme identifies, tags and tracks every single tree, utilising: • an open source platform and tree tracking app: this includes the Open Data Kitfor operational surveys, QGIS for geospatial data management and analysis195 • third party verification system – Greenstand (www.greenstand.org) to ensure transparent and robust validation of tree growth over time196 • ongoing research with the intention to improve the approach over time. ‘The pressure of rapid urbanisation coupled with a lack of development control, and lack of affordable housing, are taking an increasingly heavy toll on the forest expanse in and around Freetown. The fringes of the city are rapidly pushing into the mountains leading to a tree loss of 12% or 555 hectares per annum between 2011 and 2018. Increasing water shortages, loss of biodiversity and increasing exposure to disasters. The Freetown city council partnered with the World Bank and the Govt of Sierra Leone under the Resilient Urban Sierra Leone Project. To address some of our city’s unique challenges through our #FreetownTheTreeTown campaign. To plant and grow a million trees over Freetown and the Western Area Rural District Council peninsulas over the period 2020–2022.’ Yvonne Aki-Sawyerr, OBE, Mayor of Freetown197 71 ODI Report Cooling services, heat modification Shelter: optimising building design $$ National and local government budgets PUBLIC RESOURCES $$ Contributions from households, community and producers’ associations PRIVATE RESOURCES Options assessment A range of academic articles and general media stories describe green roof trials as pilots, including on university buildings in Cairo. For instance, the Desert Development Center at American University Cairo developed a pilot installation and their academics have promoted itsexpansion. Experts at the German University Cairo also called for the vast potential of the capital to be exploited by both public and private building managers.216 They suggest that options could be selected, among a range of green roof types, appropriate to the underlying construction (slope, roof strength, etc) of each existing building, and based upon the investor’s upfront budget/access to capital and appetite for construction and maintenance. Finance The proof of concept has been developed using private research funding in the case of American University Cairo and also with the use of international philanthropic funds from a Swiss Foundation at other sites in Cairo.217 However, the proof of concept demonstrated with these start-up funds has also spawned an enterprise called Schaduf, whose mission is to ‘help disadvantaged families to improve their quality of life as well as to make the city greener’.218 Intended outcomes The forms of green roof deployed in Cairo vary significantly in their intensity, that is, the degree to which they use shallow or deep substrates and the subsequent degree of planting and mix of plant species on them. Indeed, some of the pilot work with disadvantaged families documented with Schaduf is a hydroponic DISASTER RISK REDUCTION/ DEVELOPMENT CATEGORY FINANCE CATEGORY 72 ODI Report NBS-GI for human mobility in the urban environment Nature-based solutions in the context of human mobility, security and well-being in urban environments are ultimately about urban land use planning that fosters non-motorised transport and is designed to support public health, road/traffic safety and safe, inclusive use of public urban spaces. Urban land use planning of this kind may be in response to injuries, illnesses and deaths from motorised traffic and lack of safe walkways for pedestrians, or cycle paths. Often redevelopments to reinstate or create green space are undertaken with joint objectives for heat modification/cooling, aesthetic and recreational benefits and, often, flood risk management via increased permeability and water retention in soils. Disbenefits of NBS-GI could include the propensity of wooded or shrubland areas to encourage anti-social behaviours and thus necessitating management interventions (including policing or the use of safety lighting and other hard infrastructure in combination) to prevent this. Relevant case studies in this report: DAR ES SALAAM system, yielding vegetables for human consumption but consequently lacking some of the cooling and energy conservation potential of deeper, soilor substrate-based roofs.219 Although a range of green roof systems are now marketed to private owners as a commercial proposition,220 there was insufficient public information available about the perceived or actual payback time and valuation of benefits from these investments. The website cited provides a range of price points for different horizontally and vertically installed green roof and facade features. Given criticism in the broader literature about the costs of green roofs and lack of life cycle analysis (see above), as well as the sheer variety of green roof types available and their emergent application in north Africa and elsewhere in Africa, we suggest that much more research is needed into the life cycle cost-benefit analysis of different types, as tailored to local climates and urban contexts. Unintended outcomes Green roofs have been trialled for water retention, including mediating runoff from intensive rainfall events in eThekwini, South Africa (the subject of another case study in this report) – where the annual precipitation is far in excess of Cairo’s and the cost-benefit calculation is somewhat different. Here, investigators were interested not only in the ability of green roofs to mediate or reduce runoff, but also in their effect on the quality of the water runoff. A study by Sucheran and Sucheran (2021) in eThekwini found that the quality of runoff is worse than on control roofs without planting. The differences were significant between green roofs and control roofs and also between green roof types, leading the authors to conclude that the substrate composition may have a marked effect. Overall, they find that ‘these green roof systems do not have the ability to filter pollutants out of stormwater runoff, but rather increase their levels of concentration.’221 This negative unintended consequence merits further investigation with other roof types and in other contexts, across theregion. 73 ODI Report Conclusions NBS-GI are seen by governments and public bodies as instrumental in many cases in delivering on sustainable development objectives, including the global Agenda 2030. NBS-GI deliver many public goods within this sustainable development framework, including, as documented in this report: flood and landslide risk reduction; ambient cooling and heat regulation; agricultural and fisheries productivity; and quality of life benefits, including public health and well-being, aesthetic and recreational values. How NBS-GI are prioritised and selected We see the following trends in the selection and application of NBS-GI in Africa. NBS-GI are being prioritised and selected when part of larger strategic planning exercises that are aimed at achieving multiple public amenities, as opposed to narrow sectoral interests. We see that green and hybrid grey-green infrastructure solutions have been selected when strategic assessment has been undertaken at portfolio or strategic level, at the municipal or landscape scale, and including – in DRR terms – in a multi-hazard context. As the case studies in this volume demonstrate, green and hybrid grey-green solutions have been selected where extensive public/stakeholder consultations have revealed a range of wellbeing and development priorities and also, often, to manage a suite of risks (flood, erosion, heat related). Primary examples in this study are the participatory, strategic urban planning initiatives, such as those in Dar es Salaam andFreetown. Often, hard engineering solutions tend to prioritise a single infrastructural purpose and are more sectorally focused; the broader strategic and multidimensional purposes of NBS-GI are therefore not true comparators: comparing NBS-GI and engineered solutions is seldom comparing like for like. Self-evidently, though, some climate change adaptation and DRR challenges just cannot be addressed by green infrastructure alone: the multiple sectoral objectives and hazards (in the context of DRR) highlighted in this report were chosen because they are domains where green or green-grey options are viable but under-considered in many contexts. Governance processes that underpin options assessment, including identification of tradeoffs, are important to the perceived legitimacy of nature-based (‘green’) solutions, alone and in combination with hard-engineered (‘grey’) infrastructural solutions. Inclusive governance processes involving affected stakeholder groups, in theory, are meant to drive greater support for implementation. This indeed appears to hold true in African experience, with evidence provided (for example) through the multi-year, multi-stakeholder, layered implementation processes to enhance Dar es Salaam’s urban green infrastructure. ‘Layered’ in this context means progressive, public-funded projects that build one upon the other to scope the feasibility and public acceptance of, and progressive delivery of NBS-GI. Other cases in which NBS-GI are prioritised are when the development ‘problem’ identified is basically the degradation of a critical natural resource or resources and therefore the obvious and cost-effective ‘solution’ is restoration and 74 ODI Report rehabilitation of the degraded ecosystem functions. We see this, for instance, in the rural case study examples in this volume (and along the rural-urban continuum) where loss of forest and soil cover is undermining agricultural or fisheries productivity (e.g. coastal Kenya and Seychelles cases). We see this especially in Africa’s water sector, which is replete with examples of river catchment degradation having undermined the provision of freshwater, in which case the ‘solution’ is restoration of these critical ecosystemfunctions. We also see numerous cases where green infrastructure is deployed to increase the performance of existing or new grey infrastructure (e.g. the Darfur case in this report). These are fairly standard and well accepted use cases of replacing degraded ecosystem functions across landscapes and improving the performance of grey infrastructure, and often involve forest and soil restoration: in these cases, the diversity is, rather, in the way finance is deployed and jobs created, and in the selection and suitability of the species and materials used in the ecosystem restoration process. We have also seen, through the case studies explored here, how NBS-GI have been prioritised as project options where proof of sustainable financing and community benefits is demonstrated at an initial site and then the model is replicated or expanded in biophysically similar and socially appropriate sites. This is the case with the Gazi Bay, Kenya, blue carbon restoration and subsequent carbon credit sale, which was subsequently picked up as a model to be emulated in other sites along the Kenya coast and received private philanthropic monies from the DiCaprio Foundation for upscaling. How NBS-GI solutions are financed Options assessment processes at this broad, strategic level can be seen to prioritise NBS-GI for both their monetary and non-monetary values. It is this multidimensionality of benefits which makes NBS-GI attractive to public bodies but that also makes it difficult or sometimes inappropriate to monetise – they tend to generate public goods but not, less often, revenue streams as such and are heavily reliant on public funding for their installation and maintenance. Self-evidently, this makes NBS-GI less appealing to profit-making businesses (unless via their environmental, social and governance, as a charitable or reputation-enhancing measure). In theory, NBS-GI measures could create positive externalities for private businesses which they are then willing to pay for as part of their business model. For instance, they could be proven to greatly enhance the environmental beauty or other recreational values which are critical to the marketability and viability of a business (e.g. there is some documentation of this happening in the case of the hotel reliant on tourism in Praslin Island in the Seychelles). However, payment by private businesses of this kind for NBS-GI measures of a ‘public good’ variety is more often the subject of theoretical speculation, than proven in practice.222 That said, on a purely financial returns basis, NBS-GI appear to demonstrate good value for money compared to hard engineered solutions in achieving disaster risk reduction for lowintensity, high-frequency hazard events (this finding is derived from the wider literature).223 Although there are clear avoided losses data from the eThekwini Municipality and Dar es Salaam case studies in this volume, there is insufficient data from these cases alone to support a clear conclusion. 75 ODI Report It is possible to make the economic case for NBS-GI, if evaluating the broader social benefits (and costs) of NBS-GI investment plans. Perhaps the outstanding case identified in Africa in this study for the fullest economic assessment, including analysis of full social benefits and costs and assessing the alternative of restoring ecosystem services far beyond existing levels, was in the eThekwini Municipality business case for transformative riverine restoration. The other case studies in this report use consultative methods with stakeholder groups including civil society, and a range of economic assessments (ranging from very light touch or partial, to the deeper but not yet exhaustive like the Dar es Salaam World Bank business case). To undertake an assessment at the more complex (Durban) end of the spectrum, is, by the admission of those involved, complex, difficult and time-consuming and does not guarantee an easy ride in terms of implementation of the selected NBS-GI plans. One of the things that the South African team did was to value the costs of flooding avoided by the NBS-GI intervention. Avoided flooding losses were also an argument that was pivotal to the Dar es Salaam business case for catchment management and urban green spaces. The valuation of avoided losses and costs of recovery is much overlooked and has the potential to be far more prominent in strategic planning and financial feasibility studies. It is notable how the in-depth case studies detailed in this report reveal multiple simultaneous sources of domestic and international public funding, and in some contexts, supplemented by private philanthropic funding for NBS-GI (e.g. Bloomberg Initiative in the City of Freetown; philanthropic funding for scaling out the NBS-GI initiative in coastal Kenya). This review finds a heavy reliance on public finance and private philanthropic capital to fund, in particular: • the early scoping of people’s development priorities, production of options; options assessment processes and planning for purely green infrastructure interventions or grey-green hybrid interventions • implementation of pilot projects and proof of concept (for green infrastructure and new hybrid grey-green infrastructure). The initial implementation of the NBS-GI as well as its maintenance are sometimes developed as public works schemes providing government-funded jobs (e.g. various schemes in South Africa). Following a pilot phase, we also see financial revenue streams being identified and generated from sale of carbon credits (coastal Kenya, Madagascar) and, incipiently, from environmental impact tokens including carbon as part of a bundle of ecosystem services to be marketed to private investors (Freetown). One of the aspects of NBS-GI financing that is not well valued but we see in the case studies is the pro bono contribution of community members’ time – for instance, the mobilisation of teachers’ and students’ voluntary time. An academic study of the ‘time contributions’ of community members in Ghana and Vietnam finds that such in-kind contributions may decrease the financing needs of NBS-GI measures by 29–44%,224 but such contributions do rely upon a degree of social cohesion to be viable. The effectiveness of NBS-GI In the DRR context, NBS-GI is proving cost-effective in reducing flood risk for both inland/riverine and coastal flooding. The use of coastal-marine NBS-GI, for example mangrove conservation and restoration, to dissipate wave energy and reduce the risk of disaster impacts on low-lying coasts 76 ODI Report from storm surges is particularly emergent in the Western Indian Ocean (e.g. Kenya, Madagascar, Seychelles case studies). The Nairobi Convention consolidates both political focus and knowledge exchange in this geographic area. In coastal-marine contexts more broadly, the use of NBS-GI to couple disaster risk reduction functions with multiple other development and biodiversity functions, such as sustainable fisheries management and marine ecosystem productivity, is clearly emergent in Africa. There is also great interest, particularly on the part of African national governments, city authorities, international consortia (such as C40 Cities) and multilateral institutions (notably the World Bank), in exploring practicalities of NBS-GI to reduce urban flood risk. Favoured NBS-GI in this context may include the set-aside of urban parks and other green spaces with ‘sponge’ qualities and selected plantings as riverbank strengthening measures. However, the practicalities of implementation at urban district level vary greatly. Such contexts are inevitably characterised by land scarcity, demographic pressure including in-migration and informal settlement expansion (heightening risks), and multiple public goods values of such NBSGI beyond flood risk management are typically identified, encompassing such benefits as urban mobility, public health and safety, psycho-social well-being, heat modification and/or cooling benefits, according to location and design. These benefits are weighted against the high financial value of urban land and the actual and perceived monetary trade-offs of NBS-GI values with land development profits (e.g. accruing to private building developers) and taxation revenues on building and business development (e.g. accruing to public tax authorities). It would be worth exploring through further research, such as interviews with key informants and further case studies, whether decisions are tipped in favour of NBS-GI in African urban contexts when floods and other climate risks reach a particular level of frequency and intensity that exceeds public and political tolerance; and when a particular magnitude and sustainability of public financing is achieved to sustain the desired urban public goods that NBS-GI provide. In the water sector, there is a strong evidence base for the effective use of NBS-GI solutions in regulating water quality, especially for downstream users as a result of landscape-level interventions. There is extensive evidence of upper catchment protection through planting as an NBS-GI intervention, to reduce or reverse soil erosion and land degradation. Notwithstanding the relative abundance of documentation about planting in watersheds as a measure to reverse land degradation and improve the reliability of freshwater flows, the availability of consistently high quality, longitudinal data to aid scientific modelling is generally lacking, except in the Republic of South Africa. In South Africa, there are many contributing research institutes and universities and relatively good data management and coordination by central government authorities. When it comes to documenting the effectiveness of NBS-GI over long time periods, again, some of the best data for Africa is available with respect to watershed restoration. There is evidence for using native tree planting to restore degraded watersheds and hence reduce erosion, flash floods, and improve the quality of water downstream, over decadal timescales (10 to 20 years) in the region. Key findings from studies over longer timescales highlight that decisions made and management regimes established one or two decades ago may not have sufficiently involved local communities or led to the selection of ecologically appropriate species. These salutary 77 ODI Report evaluations highlight the importance of inclusive and ecologically sensitive decisions,225 and also raise questions about how well reflective learning and adaptive management are being applied to NBS-GI to help them reach their full potential. There is interest in expanding the use of green roofs in Africa, with evidence from South Africa and Egypt in particular to explore how green roof structures across a very wide spectrum of designs (costs, weights, complexities, range of species planted) could deliver on a range of societal private (building comfort) and public (green space, moderation of rainwater runoff) benefits. However, there was insufficient scope in this study to assess fully the evidence on the effectiveness of the different structures, designs and applications; and there was some finding that green roofs may produce unexpected disbenefits (concentrating pollutant run-off). Several categories of NBS-GI covered in this report generated case study-level insights, namely: urban cooling, human mobility and particulate matter mitigation. However, there was insufficient Africa-specific literature or definitive output or outcome-level data from the case studies to draw firm conclusions on trends in effectiveness. A further category of NBS-GI, the advancement of agricultural and fisheries productivity, through sustainable land and coastal management interventions, was highlighted via case study examples in the context of larger multipurpose schemes. These evidenced bundles of benefits, including improved water supply and disaster risk reduction. As regards agricultural and fisheries productivity, the case studies and the wider literature from the continent point to significant gains for NBS-GI approaches if and when they are tailored for local relevance and given the usual caveats for NBS-GI as a whole: about needing ongoing investment in maintenance of green infrastructure assets. Areas for further investigation The framing of NBS-GI as agile solutions that can be shaped over time in response to changing climatic conditions226 is still a proposition that merits further research across the full range of NBS-GI interventions described in this report. There is a need for robust investigation on how NBS-GI fulfill their multifunctional purposes over time, and how they have been managed adaptively to maintain efficacy: have the land footprints of NBS-GI had to change? Have the species mixes had to be changed intentionally, via management, in response to climatic trends; or have species assemblages in natural and semi-natural ecosystems changed spontaneously in response to climate change and other drivers? If so, what has been the effect (if any) on the ecological functions of NBS-GI and their delivery of expected benefits and any disbenefits, in response? To what degree can species mixes be altered through management: for instance, what is the feasibility and the implications of changing planting schemes, once vegetation is well established? What are the lessons learned around the planned and actual requirements for maintenance of NBS-GI? Investigating these questions for the diverse forms of NBS-GI described in this report would advance learning and adaptive management potential for decision-makers and managers, across Africa’s diverse cities and landscapes. 78 ODI Report Annex: Defining nature-based solutions and green infrastructure Nature-based solutions are defined by the IUCN as‘actions to protect, sustainably manage, and restore natural or modified ecosystems to address societal challenges, simultaneously providing human well-being and biodiversity benefits’. They are seen as crucial for sustainable development.227 The term ‘nature-based solutions’ was first used as a way of describing approaches to climate change adaptation and mitigation that harnessed the power of ecosystem functions. However, early applications focused narrowly on using the natural environment for climate change mitigation objectives, to the detriment of other social and environmental uses. These included, for instance, tree-planting projects under the Clean Development Mechanism of the Kyoto Protocol of the UNFCCC, which were undertaken to sequester carbon and enable developing countries to sell carbon credits on the international market. There was something of a backlash to this approach, when some interventions were found to undermine biodiversity (e.g. by planting monocultures of trees that do not support a diversity of other species) and also found to restrict local communities’ and especially local women’s uses of forest lands.228 In response to documented harms from poorlyconceived NBS-GI, IUCN led in developing its Global Standard (first edition, 2020). This standard defines nature-based solutions more expansively as delivering biodiversity, social and climate benefits in parallel. The emphasis is on recognising and optimising biodiversity and social values in balance with the climate mitigation and adaptation values of interventions. The standard requires, at minimum, that interventions to deliver climate benefits should not cause harm in the social and ecological dimensions. Nature-based versus nature-derived and nature-inspired NBS-GI are different from ‘nature-derived’ and ‘nature-inspired’ solutions.229 Nature-derived solutions such as wind, wave and solar energy capture natural forces in the environment for low-carbon energy production. Nature-inspired solutions include innovative design and use of structures and materials that mimic or are based on biological systems. Sometimes the latter is called ‘biomimicry’. Neither of these relies on ecosystem functions.230 These definitions are important as they explain why renewable energies, for instance, are excluded from the present study. Other preferred terms apart from ‘nature-based solutions’ The IUCN guidance is well-intentioned, it is pragmatic, and it was developed in response to perceived misuse of the concept of NBS-GI. Nevertheless, the term ‘nature-based solutions’ is controversial among some stakeholder groups. Critics of the term argue that many indigenous and local communities have championed living and livelihood practices based on the deep respect of nature for centuries to millennia. Some country governments, indigenous peoples, and civil society organisations harbour a deep degree of suspicion about ‘when, where, how, and for whom nature- 79 ODI Report based solutions are effective’231 and especially in light of instances when NBS-GI have been used for greenwashing and associated with human rights violations and damage to biodiversity. Therefore, these groups sometimes prefer to talk about ‘ecosystem-based adaptation’, ecosystembased mitigation and other terms, rather than the umbrella phrase ‘nature-based solutions’. In its Summary for Policy Makers of Climate Change 2022, Impacts, Adaptation and Vulnerability to Climate Change, the Intergovernmental Panel on Climate Change writes: ‘Ecosystem based Adaptation (EbA) is recognised internationally under the Convention on Biological Diversity (CBD14/5). A related concept is Nature-based Solutions (NBS-GI), which includes a broader range of approaches with safeguards, including those that contribute to adaptation and mitigation. The term ‘Nature-based Solutions’ is widely but not universally used in the scientific literature. The term is the subject of ongoing debate, with concerns that it may lead to the misunderstanding that NBS-GI on its own can provide a global solution to climate change.’232 80 ODI Report Annex: Methods of the present study The study began with an initial literature review, based on a keyword search strategy using the terms ‘nature-based’, ‘infrastr*’ and ‘Africa’ on both Google Scholar and on the EBSCO database.233 This scan of the academic literature generated few relevant results. Most results lacked an Africa focus or sufficient analysis of pragmatic development considerations for decision-makers considering NBS-GI in specific African contexts. Therefore, the authors pivoted to a literature review method, based on snowballing and grey literature capture. This essentially involved focusing on the most relevant works identified through Google Scholar and EBSCO and drilling into their respective references, as well as the publications in which they are referenced (snowballing); together with key informant interviews and literature recommendations with expert practitioners working in African cities and countries. Snowballing is a process that ‘involves actively seeking advice on relevant publications in a particular field, or on a particular topic from key experts – which will then be reviewed – and subsequently looking at the reference lists of those publications’.234 For more on the snowballing and grey literature aspects of literature review methods for international development subjects, see Hagen-Zanker and Mallett (2013).235 The case studies in the report draw heavily on written evaluations by governments, NGOs and development finance institutions, as well as key informant interviews, to shed light on decisionmaking processes, outcomes and lessons learned. 87 ODI Report 173 IPCC (2022b). Climate Change 2022: Mitigation of Climate Change. 174 Onyango, S. A., Mukundi, J. B., Adimo, A. O., Wesonga, J. M., & Sodoudi, S. (2021). ‘Variability of In-Situ Plant Species Effects on Microclimatic Modification in Urban Open Spaces of Nairobi, Kenya.’ Current Urban Studies, 9, 126–143. https://www.scirp.org/html/8-1150506_107950.htm 175 Cook, P., Howarth, M., and Wheater, C.P. (2019) ‘Biodiversity andhealth intheface ofclimate change: Implications forpublic health’ Chapter 11 in Marselle, M.R., Stadler, J., Horst, K., Irvine, K., Bonn, A. Biodiversity and health in the face of climate change. Cham, Switzerland: Springer Nature Switzerland. https://doi.org/10.1007/978-3-030-02318-8 176 Ibid. 177 IPCC (2022b). Climate Change 2022: Mitigation of Climate Change. 178 And associated Msimbazi Basin Development Project, a project vehicle to advance the objectives of the Msimbazi Opportunity Plan, which is funded by the World Bank. 179 World Bank (n.d. (a)) ‘Nature-based Solutions: A cost-effective approach for disaster risk and water resource management’ [webpage]. https://www. worldbank.org/en/topic/disasterriskmanagement/brief/nature-based-solutionscost-effective-approach-for-disaster-risk-and-water-resource-management World Bank (2022) ‘Msimbazi Basin Development Project’ (Webpage and related online resources) www.worldbank.org/en/country/tanzania/brief/ msimbazi-basin-development-project (accessed 17 May 2023) Government of Tanzania (2020). ‘Draft resettlement policy framework.’ Dar Es Salaam: President’s Office – Regional Administration and Local Government. www.tamisemi.go.tz/storage/app/media/uploaded-files/Resettlement%20 Policy%20Framework%20-%20%20Msimbazi%20Project.pdf Government of Tanzania (2018). The Msimbazi Opportunity: Transforming the Msimbazi Basin into a Beacon of urban resilience. Government of Tanzania, Dar Es Salaam. 180 Frantzeskaki,N., et al. (2019). ‘Nature-based solutions for urban climate change adaptation’. 181 Karutz R., Berghöfer A., Moore L.R., and van Wyk, E. (2019). A thematic atlas of nature’s benefits to Dar es Salaam. Leipzig and Cape Town: Helmholtz Centre for Environmental Research and ICLEI Africa Secretariat. 78 pages. https://e-lib. iclei.org/value-nature-urban-life/DaresSalaam-ThematicAtlas.pdf 182 Government of Tanzania (2020). 183 Government of Tanzania (2018). The Msimbazi Opportunity. p.3. 184 Ibid. 185 Turpie, J., Kroeger, T., De Risi, R., de Paola, F., Letley, G., Forsythe, K., Day, L., (2016).Return on Investment in Green Urban Development: Amelioration of Flood Risk in the Msimbazi River Catchment, Dar Es Salaam, Tanazania.Promoting Green Urban Development in Africa. Washington, DC: World Bank. https://openknowledge.worldbank.org/handle/10986/26702 186 Ibid. 187 Ibid. 188 World Bank (2022). ‘New World Bank financing will strengthen climate change adaptation and resilience in flood-prone Dar Es Salaam’ [Press release, online]. www.worldbank.org/en/news/press-release/2022/10/04/new-world-bankfinancing-will-strengthen-climate-change-adaptation-and-resilience-in-floodprone-dar-es-salaam (accessed 20 December 2022). 189 Limbumba, T. M. (2019). ‘Bottom-up Planning for Storm water Management in Informal Settlements: Lessons from the Design Charrette in Goba, Dar es Salaam City.’ Institute for Human Settlements Studies Ardhi University, Dar es Salaam, Tanzania. Conference presentation: Resilient Cities, 28th June 2019. https://resilientcities2019.iclei.org/wp-content/uploads/RC2019_Presentations_ H4_Limumba.pdf 190 Freetown City Council (2019). Transform Freetown: An overview (2019–2022). Freetown, Sierra Leone: Freetown City Council. https://fcc.gov.sl/transformfreetown/ Freetown City Council (2022a). ‘Freetown Sierra Leone wins Bloomberg Philanthropies Global Mayors’ Challenge’ [Web article/press release]. 19 January 2022. https://fcc.gov.sl/freetown-sierra-leone-wins-bloombergphilanthropies-global-mayors-challenge/ Toya, A., Cowan, N.M., Duma, L. and Fisseha, T. (2021). ‘#FreetownTheTreeTown campaign: Using digital tools to encourage tree cultivation in cities.’ Washington, DC: Global Environment Facility. www.thegef.org/newsroom/blog/ freetownthetreetown-campaign-using-digital-tools-encourage-tree-cultivationcities Key informant interview: Eric Hubbard, Project Manager, Freetown the Treetown (December 2022). GFDRR (2021) ‘Freetown the Treetown: Using EO & AI to Detect and Monitor UrbanForest Canopy for Freetown’ [video]. An interview with Freetown Mayor Yvonne Aki-Sawyerr www.youtube.com/watch?v=CwWWH_ q6mkw&list=PLlxZ8h0dxpsCBPsiw6aWnxxQLnFqhBk6U&index=2 And further original writing by Eric Hubbard. 191 Freetown City Council (2019). Transform Freetown: An overview (2019–2022). 192 Ibid. 193 Ibid. Macarthy, J., Koroma, B., Cociña, C., Butcher, S., & Apsan Frediani, A. (2022). The “slow anatomy of change”: urban knowledge trajectories towards an inclusive settlement upgrading agenda in Freetown, Sierra Leone. Environment and Urbanization, 34(2), 294–312. https://doi.org/10.1177/09562478221106611 194 Freetown City Council (2019). Transform Freetown: An overview (2019–2022). 195 Toya, A., et al. (2021). ‘#FreetownTheTreeTown campaign’. 196 Key informant interview: Hubbard (2022). 197 GFDRR (2021) ‘Freetown the Treetown’. 198 Key informant interview: Hubbard (2022). 199 GFDRR (2021) ‘Freetown the Treetown’. 200 Toya, A., et al. (2021). ‘#FreetownTheTreeTown campaign’. 201 World Bank (u.d.) ‘Resilient Sierra Leone program’ [Project webpage] https:// projects.worldbank.org/en/projects-operations/project-detail/P168608 (accessed 20 December 2022). 202 Freetown City Council (2019). Transform Freetown: An overview (2019-2022). 203 Ibid. 204 Freetown City Council (2022b). Transform Freetown: Third Year Report (2021-2022). Freetown, Sierra Leone: Freetown City Council. https://fcc.gov.sl/ transform-freetown/ 205 Toya, A., et al. (2021). ‘#FreetownTheTreeTown campaign’. 206 Ibid. 207 Freetown City Council (2022a). ‘Freetown Sierra Leone wins Bloomberg Philanthropies Global Mayors’ Challenge’. https://fcc.gov.sl/freetown-sierraleone-wins-bloomberg-philanthropies-global-mayors-challenge/ 208 As of May 2023 (time of writing). 209 Carter, T. and Keeler, A. (2008). ‘Life-cycle cost–benefit analysis of extensive vegetated roof systems’ in Journal of Environmental Management, 87(3): 350–363. https://doi.org/10.1016/j.jenvman.2007.01.024 Toxopeus, H. and Polizin, F. (2021). ‘Reviewing financing barriers and strategies for urban nature-based solutions’. 210 Toxopeus, H. and Polizin, F. (2021). ‘Reviewing financing barriers and strategies for urban nature-based solutions’. Specht, K., Siebert,R.,Hartmann,I., Freisinger, U.B., Sawicka,M., Werner, A., Thomaier,S., Henckel,D., Walk,H., Dierich, A. (2014). ‘Urban agriculture of the future: an overview of sustainability aspects of food production in and on buildings’ Agriculture and Human Values31(1): 33–51. 211 Rizzo, G.; Cirrincione, L.; La Gennusa, M.; Peri, G.; Scaccianoce, G. (2023). ‘Green Roofs’ End of Life: A Literature Review’. Energies 2023, 16, 596. https://www. mdpi.com/1996-1073/16/2/596 212 Radwan, A. (2017). ‘Green roofs: A sustainable tool of healthier cities, applications in Egypt’ [conference paper] First international conference: Towards a better quality of life. 24–26 November 2017 Technische Universität Berlin Campus El Gouna, Egypt; Deutsche Welle (2019) ‘Des jardins sur les toits de la capitale egyptienne’ [webpage and video] www.dw.com/fr/des-jardins-sur-les-toits-de-la-capitale- %C3%A9gyptienne/av-51071836; Kayed, S.M., Abueldahab, S.A., Eichner, M., Sarhan, Y. (2022). ‘Green Rooftops: Enhancing Buildings’ Sustainable Performance in Egypt’ International Journal of Engineering Research & Technology (IJERT) 11(02), IJERTV11IS020098; Sucheran, A. and Sucheran, R. (2021). ‘Green roofs and stormwater runoff quality in the urban landscape in South Africa’. Applied Journal of Environmental Engineering Science 7(2): 176–196. 213 Kayed, S.M., et al. (2022). ‘Green Rooftops: Enhancing Buildings’. 214 Deutsche Welle (2019) ‘Des jardins sur les toits de la capitale egyptienne’. 88 ODI Report 215 Radwan, A. (2017). ‘Green roofs: A sustainable tool of healthier cities, applications in Egypt’. 216 Kayed, S.M., et al. (2022). ‘Green Rooftops: Enhancing Buildings’. 217 Deutsche Welle (2019) ‘Des jardins sur les toits de la capitale egyptienne’. 218 Ibid. 219 Ibid. 220 See, for instance, the commercial supplier www.schaduf.com 221 Sucheran, A. and Sucheran, R. (2021). ‘Green roofs and stormwater runoff quality in the urban landscape in South Africa’. 222 Dupar, M. (2018). ‘Adaptation finance: who benefits and who’s willing to pay?’ [web article] https://cdkn.org/story/key-questions-for-adaptation-finance 223 IPCC (2022a). Climate Change 2022: Impacts, Adaptation and Vulnerability. 224 Hagedoorn, L. et al (2021) ‘Reducing the finance gap for nature-based solutions with time contributions’ Ecosystem Services52(3):101371 https://doi. org/10.1016/j.ecoser.2021.101371 225 Seddon, N (2022). ‘Harnessing the potential of nature-based solutions for mitigating and adapting to climate change’ in Science 376(6600): 1410–1416. https://doi.org/10.1126/science.abn9668 226 World Bank (n.d. (b)) ‘Nature-based Solutions Program’ with Brenden Jongman, Senior Disaster Risk Management Specialist [video] https://youtu.be/ gNmBBQVu8PA (accessed 3 January 2023). 227 IUCN (2020). The IUCN Global Standard for Nature-based solutions. 228 Dankelman, ed. (2010), Gender and Climate Change. Abingdon: Earthscan; Aguilar, L. (2010). ‘Establishing the linkages between gender and climate change adaptation and mitigation’, 173–193; in Dankelman, I. (2010). Gender and climate change: An introduction. Abingdon, Oxon: Earthscan. Aguilar, L., M. Granat, and C. Owren. (2015). Roots for the future: The landscape and way forward on gender and climate change. Washington, DC: IUCN and GGCA. 229 IUCN (2020). The IUCN Global Standard for Nature-based solutions. 230 Ibid. 231 Seddon, N. (2022). ‘Harnessing the potential of nature-based solutions for mitigating and adapting to climate change’. 232 IPCC (2022a). Climate Change 2022: Impacts, Adaptation and Vulnerability. 233 ODI subscribes to EBSCO, where the authors accessed the following databases: STM Source, Business Source Corporate Plus, Environment Complete, Humanities Source, Political Science Complete, and SOCIndex databases. We searched EBSCO specifically for academic journal articles on the keywords indicated. 234 Hagen-Zanker, J. and Mallett, R. (2013). How to do a rigorous, evidence-focused literature review in international development. London: ODI. https://odi.org/ en/publications/how-to-do-a-rigorous-evidence-focused-literature-review-ininternational-development-a-guidance-note/ See p.10. 235 Ibid. ODI is an independent, global think tank, working for a sustainable and peaceful world in which every person thrives. We harness the power of evidence and ideas through research and partnership to confront challenges, develop solutions and create change ODI 203 Blackfriars Road London SE1 8NJ +44 (0)20 7922 0300 [email protected] odi.org odi.org/facebook odi.org/twitter