How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? A systematic map

www.clevercities.eu How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? A systematic map EUROPEAN PARTNERSHIP How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 2 www.biodiversa.eu Document Information Grant Agreement number: 101052342 Project acronym: Biodiversa+ Project full name: The European Biodiversity Partnership Biodiversa+ duration: 7 years Biodiversa+ start date: Start date: 1st October 2021 For more information about Biodiversa+ Website: http://www.biodiversa.eu/ Email: [email protected] Twitter: @BiodiversaPlus LinkedIn: Biodiversa+ Deliverable title: D4.11: How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? A systematic map Authors: Haddaway, N.R., Stoudmann, N., Alkhateeb, G., Sampson, H., Turner, K., Skidan, V., Savilaakso, S. Work package title: Work Package 4 Connecting R&I programs, results and experts to policy Task or sub-task title: Subtask 4.1.2: Desk studies and production of knowledge syntheses Lead partner: FRB Date of publication: 31/03/2025 Disclaimer Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them. Cover page illustration: © [https://pixabay.com/photos/cinque-torri-italy-mountains-meadow-7348088/, Pixabay] How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 3 www.biodiversa.eu What is Biodiversa+ The European Biodiversity Partnership, Biodiversa+, supports excellent research on biodiversity with an impact for policy and society. Connecting science, policy and practise for transformative change, Biodiversa+ is part of the European Biodiversity Strategy for 2030 that aims to put Europe’s biodiversity on a path to recovery by 2030. Co-funded by the European Commission, Biodiversa+ gathers 81 partners from research funding, programming and environmental policy actors in 40 European and associated countries to work on 5 main objectives: 1. Plan and support research and innovation on biodiversity through a shared strategy, annual joint calls for research projects and capacity building activities 2. Set up a network of harmonised schemes to improve monitoring of biodiversity and ecosystem services across Europe 3. Contribute to high-end knowledge for deploying Nature-based Solutions and valuation of biodiversity in the private sector 4. Ensure efficient science-based support for policy-making and implementation in Europe 5. Strengthen the relevance and impact of pan-European research on biodiversity in a global context. More information at: https://www.biodiversa.eu/ How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 4 www.biodiversa.eu Table of contents What is Biodiversa+ ........................................................................................................... 3 Executive summary ........................................................................................................... 5 1. Introduction ............................................................................................................... 6 2. Objectives .................................................................................................................. 7 3. Methods ..................................................................................................................... 8 3.1. Deviations from the protocol ............................................................................................................ 8 3.2. Search strategy overview................................................................................................................. 8 3.3. Article screening and study eligibility criteria ................................................................................. 11 3.4. Data coding and presentation of results ........................................................................................ 13 4. Results ..................................................................................................................... 16 4.1. The review process ........................................................................................................................ 16 4.2. Geographical distribution of the evidence base ............................................................................ 17 4.3. Publication trends and study duration characteristics ................................................................... 19 4.4. Study attributes and methodological approaches ......................................................................... 21 4.5. Temporal trends in study designs and sampling methods ............................................................ 24 4.6. Cross-variable patterns in the evidence base ............................................................................... 28 5. Discussion and Conclusions ................................................................................. 44 5.1. Rise of monitoring and different methods ...................................................................................... 44 5.2. Control-intervention studies dominant in study designs ................................................................ 45 5.3. Uneven geographical representation ............................................................................................. 45 5.4. Protected area representation ....................................................................................................... 46 5.5. Future directions and implications for conservation ...................................................................... 46 Author contribution ......................................................................................................... 47 Conflict of interest ........................................................................................................... 47 Funding ............................................................................................................................. 47 Acknowledgments ........................................................................................................... 47 References ....................................................................................................................... 48 Annex 1. A list of articles to test comprehensiveness of the search string ............... 51 Annex 2. Definitions of meta-data values ...................................................................... 52 How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 5 www.biodiversa.eu Executive summary Background: Protected areas (PAs) are fundamental in preserving biological diversity, supporting ecosystem services, and mitigating human impacts in today’s world. However, the mere designation of PAs is insufficient for achieving conservation goals. The effectiveness of PAs needs to be ensured through employment of robust management practices and the deployment of scientifically sound monitoring methodologies. Methods: This systematic map aims to collate and synthesize evidence from across the globe on the (monitoring) methods and metrics used to assess the effectiveness of terrestrial PAs in biodiversity conservation. By doing so, we seek to identify the consistency of monitoring schemes across different geographies and ecosystems (e.g. forested, desert, alpine and wetland biomes etc), to determine how well standardized monitoring methods have been adopted. This worldwide evidence base will not only inform the evaluation of PAs within Europe but also contribute to the global discourse on biodiversity conservation, facilitating the exchange of knowledge and best practices. Results: The systematic map identified 275 articles assessing protected area effectiveness for primarily terrestrial PAs (i.e. a greater surface area than 50% must be terrestrial) across the globe. Most studies were conducted in Africa, Asia, and Europe, with fewer in Oceania and North America. Studies were predominantly conducted at local or regional scales, with fewer multinational assessments. ControlIntervention (CI) designs were the most common, often incorporating time-series analysis, while BeforeAfter Control-Impact (BACI) designs remained rare. Geographic Information Systems (GIS) and direct observation were widely used, with an increasing reliance on satellite-based measurements. Studies focused largely on forested biomes, with fewer examining alpine, desert, and wetland ecosystems. Species-level assessments were limited, with many studies relying on land cover change and forest cover as a proxy for biodiversity. Genetic diversity, species traits, and ecosystem functional metrics were notably underrepresented. Conclusions: There has been a marked increase in research on PA effectiveness in recent years. However, methodological gaps persist, particularly in the application of BACI designs and the evaluation of biodiversity beyond habitat-level metrics. The reliance on GIS and remote sensing, while useful for large-scale monitoring, may overlook speciesand community-level dynamics at the local-scale. These monitoring methods may miss small-scale changes in species composition, abundance and/or richness, highlighting the complementarity of direct observation with field-based sampling methods for conservation decision making. The predominance of studies focused on a single PA reflects a tendency towards smaller-scale, site-specific assessments. While these provide detailed insights into specific locations, they may miss opportunities to evaluate broader, landscape-level impacts of PAs which could help identify connectivity issues, cumulative impacts and broader trends. Additionally, the underrepresentation of certain ecosystems and PA categories highlights the need for broader, standardized approaches to biodiversity monitoring. Addressing gaps in underrepresented biomes, such as alpine regions and deserts, could enhance our understanding of PA effectiveness across diverse ecological contexts. Future research should emphasize more diverse and integrative biodiversity indicators, improve representation across underexplored regions and ecosystems, and enhance methodological rigor in assessing PA effectiveness. Keywords: Biodiversity conservation, monitoring and evaluation, impact evaluation, protected area effectiveness, evidence synthesis, evidence mapping How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 6 www.biodiversa.eu 1. Introduction In the context of global biodiversity conservation, protected areas (PAs) are considered foundational to preserving ecological diversity, supporting ecosystem services, and mitigating human impacts (Watson et al. 2014). The strategic establishment and management of PAs are guided by international and regional policy frameworks, such as the Kunming-Montreal Global Biodiversity Framework (CBD 2022) and the European Union’s biodiversity strategy for 2030 (EUR-LEX, European Union Law 2020). These frameworks set quantitative goals for PA coverage and underscore the necessity for effective and equitable management practices that are ecologically representative and well-connected (Adams et al. 2023). However, the mere designation of PAs is insufficient for achieving conservation goals. The efficacy of these areas in biodiversity conservation is contingent upon robust management practices, the deployment of scientifically sound monitoring methodologies, and the adaptation of conservation strategies to address emergent issues (Mascia et al. 2014). The challenge of evaluating PA effectiveness toward biodiversity conservation lies in measuring direct impacts amidst complex ecological dynamics, the variability of conservation goals, and the scarcity of baseline data and long-term monitoring efforts (Geldmann et al. 2019). This endeavour is further complicated by the wide range of indicators and metrics used to gauge effectiveness, pointing to a critical need for systematic consolidation of this information (Rodrigues & Cazalis 2020). In the context of this study, we define effectiveness as the degree to which PAs contribute towards meeting global biodiversity targets, encompassing a wide spectrum of goals, from averting species extinction to preserving threatened ecosystems (Maxwell et al. 2020). However, while the focus of this research is on biodiversity outcomes, PAs can also play a role in addressing social dimensions, such as supporting local communities, safeguarding indigenous rights, and contributing to ecological development (Borrini-Feyerabend et al. 2013). However, PAs do not inherently preserve cultural values and may have unintended outcomes. Rather, actions like supporting local communities and safeguarding Indigenous rights shape these values (Dawson et al. 2021). Nonetheless, while critically important, these social aspects fall outside the primary scope of this study. This systematic map aims to collate and synthesize global evidence on the methods and metrics used to assess the effectiveness of terrestrial PAs in biodiversity conservation. By doing so, we seek to identify the consistency of monitoring schemes across different geographies and determine how well standardized monitoring methods have been adopted. This broad evidence base will not only inform the management and evaluation of PAs within Europe but also contribute to the global discourse on biodiversity conservation, facilitating the exchange of knowledge and best practices. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 7 www.biodiversa.eu 2. Objectives The objective of this evidence synthesis was to collate and describe the evidence base relating to terrestrial protected areas and biodiversity measurement. The systematic map’s primary question was: How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? Secondary questions include: 1. Which biodiversity monitoring methods and metrics have been well used to assess protected area effectiveness, and which are under-represented or absent from the evidence base or particular contexts? 2. What is the level of consistency in monitoring schemes across geographical areas, protected area designations, and managing and researching institutions? 3. What standardised monitoring methods have been developed in the literature and how well have they been adopted? This question can be broken down into the following key elements: Population: Terrestrial systems globally Intervention: Protected area establishment/presence Comparator: Outside protected areas, before establishment of protection, or in the absence of a protected area Outcome: Methods for measuring terrestrial protected area conservation effectiveness using direct or indirect biodiversity metrics How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 8 www.biodiversa.eu 3. Methods This review has been conducted according to the methods outlined in a published protocol (Haddaway et al. 2024) and based on the methods for systematic mapping published by the Collaboration for Environmental Evidence (James et al. 2016). 3.1. Deviations from the protocol We made use of a subsampling approach to enable representative assessment of the evidence base from a manageable volume of abstracts. We manually screened 7,229 abstracts (17% of all search results) before training a machine learning model that was then used to predict the relevance of the remaining records. We then randomly sampled the results of this model, screening these additional abstracts at full text level. This resulted in a total of 655 records (19%) of the evidence base being considered at the full text screening stage. Because of our approach to sampling, we do not consider there to be any issues with a lack of representativeness or bias in the subset presented herein. We planned to use Publish or Perish to import Google Scholar results. However, the software was not working properly at the time of use, so records were screened in situ, retaining only those that were deemed to be relevant. 3.2. Search strategy overview We searched for evidence across a range of sources, including bibliographic databases, a web-based academic search engine, organisational websites, and using citation chasing. This range of sources aims to cover a diversity of terminological descriptions of the topic, publication platforms, traditional academic and grey literature, and citation networks of related works that might otherwise evade other search methods. The search string used in bibliographic databases was based on several previously published systematic reviews on related topics and the team’s expertise in this field. The string has been tested for functionality and compared against a benchmark list (cf. Annex 1) to ensure a relevant set of primary studies are returned within the search results. 3.2.1. Bibliographic database search string The search string adapted to Scopus was as follows: (("protected area*" OR "national park*" OR "conservation area*" OR "wilderness area*" OR "natural monument*" OR "natural park*" OR "natural feature*" OR "protected landscape*" OR "nature park*" OR "nature reserv*" OR "biosphere reserv*" OR "world heritage site*" OR "natura 2000" OR "ramsar") W/15 (effect* OR affect* OR impact* OR effic* OR mitig* OR perform* OR success* OR indicator* OR evaluat* OR assess* OR fail* OR analy*)) AND (biodiversity OR ecosystem* OR species OR habitat* OR communit* OR "biological diversity" OR conservation) How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 9 www.biodiversa.eu 3.2.2. Bibliographic databases We searched across a suite of different bibliographic databases using the tried-and-tested search string above. The search string was adapted to the syntax of each individual resource and these search strings and the number of hits is reported in Additional File 1. Table 1. Bibliographic databases that will be searched for relevant literature. Database Search details Access/ subscription notes Scopus Title, abstracts, keywords University of Tasmania Web of Science Core Collection  Science Citation Index Expanded (SCI-EXPANDED) - 1945-present  Social Sciences Citation Index (SSCI) - 1956-present  Arts & Humanities Citation Index (AHCI) - 1975present  Conference Proceedings Citation Index – Science (CPCI-S) - 1990-present  Conference Proceedings Citation Index – Social Science & Humanities (CPCI-SSH)- 1990-present  Book Citation Index – Science (BKCI-S) - 2005present  Book Citation Index – Social Sciences & Humanities (BKCI-SSH) - 2005-present  Emerging Sources Citation Index (ESCI) - 2015present Topic University of Helsinki CAB Abstracts through Ovid Title OR Abstract University of Helsinki ProQuest (Dissertations and Theses) Topic University of Helsinki 3.2.3. Benchmark testing During development of the search string, we assembled a set of 9 articles of known relevance (Annex 1) that we used as a benchmark list to test the functioning of the search string in Scopus. During testing, minor modifications were necessary to the search to retrieve all benchmark records, reflected in the final string provided above. We therefore consider this string sufficiently comprehensive. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 16 www.biodiversa.eu categorical variables. We also present the evidence base cartographically, producing an interactive visualisation displaying each study location, with descriptive information about each study in pop-ups (also known as an ‘evidence atlas’, Haddaway et al. 2018). Using these tables and visualisations, we have sought to identify knowledge clusters (topics where sufficient evidence exists to allow meaningful meta-analysis), but primarily also knowledge gaps (areas that are un-/ or underrepresented with fewer studies than might be needed/hoped/expected). By visualising methods used over various other variables (including time, geography, protected area type, taxa, etc.) we are able to identify combinations for which there are relatively fewer studies than expected. Heat maps facilitate this process by displaying the number of studies as colour graded tiles, with lighter shades indicating potential knowledge gaps and darker shades suggestion clusters. In all cases, the suitability of these topics is discussed relative to their importance conceptually as well as numerically (i.e. are they meaningful gaps). 4. Results 4.1. The review process The flow of records through the review is outlined in a ROSES flow diagram in Figure 2. We identified over 66,000 search results from across bibliographic databases, along with 1,759 records via citation chasing from our benchmark article list. After deduplication, we were left with 42,718 unique records. After manual and machine learning assisted title and abstract screening, we were left with 10,196 potentially relevant records to screen at full text. After subsampling (combining the 480 included abstracts from manual title and abstract screening and 183 randomly sampled records from machine learningscreened titles and abstracts), we obtained 663 full texts, which were screened manually. We identified 4 relevant full texts through grey literature searching, resulting in a total of 275 articles and 280 studies included in the final systematic map database. See Additional File 3 for the database of included studies. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 17 www.biodiversa.eu Figure 2. Adapted ROSES flow diagram showing the fate of all records included in the systematic map. The numbers presented in the following figures are based on a subsample of the evidence base (c. 19% of all relevant full texts). 4.2. Geographical distribution of the evidence base We have summarised the evidence base in an interactive evidence atlas (see the snapshot in Figures 3 and 4). The studies covered a range of scales. Most were conducted at the local (105) or regional/subnational scale (105). National-scale studies accounted for 39 studies, while 36 studies were multinational. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 18 www.biodiversa.eu Figure 3. Evidence atlas showing the geographical location of all studies included in the systematic map, including the study scale (interactive version available here: https://datawrapper.dwcdn.net/Th2Jd/1/). Studies without latitude or longitude are displayed in the central Atlantic Ocean. Fifteen regional studies without coordinates are not shown. Figure 4. Choropleth showing the frequency of studies represented within the systematic map across countries. Not shown are the studies covering regions as a whole - Africa, 7: Antarctica, 1: Asia, 4: Europe, 7: Global, 8: North America, 1: Oceania, 1: South America, 4. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 19 www.biodiversa.eu The geographical distribution of articles was uneven, with the largest share conducted in Africa (63 articles), followed by Asia (50 articles) and Europe (46 articles) (Table 4). South America was represented by 40 articles, while Central America (21 articles) and North America (19 articles) had moderate representation. Oceania (6 articles), MENA (Middle East and North Africa) (14 articles), and Antarctica (1 article) had limited coverage. A small number of articles (17 articles) spanned multiple regions. Table 4. Articles per continent. SSA = Sub-Saharan Africa. MENA = Middle East and North Africa. Continent Articles SSA 63 Asia 50 Europe 46 South America 40 Central America 21 North America 19 Multiple 17 MENA 14 Oceania 6 Antarctica 1 4.3. Publication trends and study duration characteristics Very few articles published pre-2000 were identified (Figure 5). Between 2000 and 2011, there was a slight increase, particularly after 2006, through the growth remained modest. From 2012 onwards, however, the number of articles published rose sharply, with a nearly continuous upward trend. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 20 www.biodiversa.eu Figure 5: Number of articles published per year. Most studies were short-term, with the majority lasting less than one year (Figure 6). A significant proportion spanned durations of up to 20 years. Studies extending up to 45 years were much less common, and only a very small number exceeded 50 years. Figure 6. Number of full study years across articles (12 months or more between the year a study commenced and the year it was completed, 0 = less than one year). How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 21 www.biodiversa.eu Figure 7. Number of study months across articles (total number of months in which data were recorded). When considering the number of months of study, most lasted less than one month, and the second largest share lasted under a year (Figure 7). Beyond this, the numbers decline sharply, with only a few long-term studies extending beyond 12 months. 4.4. Study attributes and methodological approaches Most studies focused on a single PA (Figure 8). Among studies that examined multiple PAs, a small but notable subset focused on three PAs, with numbers gradually decreasing as the number of PAs per study increased. Despite this decline, studies encompassing up to 150 PAs were represented. Beyond this range, the numbers diminished significantly, with only a handful of studies exceeding 150 PAs. The largest study included in the evidence base considered 40,232 PAs. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 22 www.biodiversa.eu Figure 8. Number of protected areas studied in each study. X-axis is a log(10) scale. The studies were predominantly conducted in the tropical-subtropical forest biome (122 studies), followed by temperate-boreal forests and woodlands (70) (Figure 9). Savannas and grasslands accounted for 68 studies, while deserts and semi-deserts were represented in 23 studies. Shrublands were examined in 40 studies, and alpine/polar regions in 22 studies. Freshwater ecosystems, including rivers and streams (25) and lakes (13), received less attention, as did wetland and coastal biomes, with palustrine wetlands (26) and brackish tidal zones (10) being less frequently studied. As certain studies examined multiple biomes, the total count exceeds the number of included studies. Some sampling methods were far more prevalent than others. The most frequently used method was Geographical Information Systems (GIS), employed in 105 studies (Figure 9). Sampling plots were used in 58 studies, and stratified sampling in 50. Random sampling was applied in 34 studies, while transects accounted for 37 studies. Systematic sampling was reported in 42 studies, and point counts were used in 21 studies. Seven studies used third party databases. Finally, mark-recapture and GPS collars were the least frequently used methods, appearing in only 3 and 1 studies, respectively. Most studies focused on subjects within the Plantae (170) and Animalia (110) Kingdoms. Few articles looked at Fungi, Protista, and Bacteria, each accounting for 3 studies. The overwhelming majority of studies (279) were observational in nature, while experimental designs were much less common, appearing in 3 studies. Since some articles contained both observational and experimental components, the total number of studies exceeds the number of articles. In terms of experimental designs, most studies employed a combination of control-intervention (CI) and time-series designs (132). Ninety-nine studies used a CI design alone. Time-series designs made up 20 studies, while 23 combined time-series data with Before-After Control-Impact (BACI) designs. Pure BACI and Before-After (BA) designs were the least common, each represented by 4 studies www.clevercities.eu Figure 9. Studied biome, sampling method, kingdom, study type, experimental design, and scale across articles. www.clevercities.eu The most frequently used survey method was direct observation, employed in 129 studies (Figure 10). Satellite measurements were also commonly used, accounting for 105 studies. Indirect observation methods were used in 24 studies, while direct listening was applied in 16 studies. Questionnaire-based methods accounted for 4 studies, and camera traps were used in 11 studies. Hand searching was used in 15 studies, and net fishing in 11. Basket traps were used in 4 studies, live trapping in 7, sweep netting in 8, and DNA extraction in 5 studies. Less frequently applied techniques included pit-traps (2), kick sampling (2), active fishing (3), and spring-loaded bar traps (1). Figure 10. Number of articles by survey method used. 4.5. Temporal trends in study designs and sampling methods The earliest studies had CI designs and those were dominant throughout time either with or without time series (Figure 11). The first study with a solely time series design is from 2001, but they don’t increase in number much until 2014 onwards. The earliest study with BACI design appears in 2008. From 2014, studies with BACI design increased and were mostly implemented with a time series design. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 25 www.biodiversa.eu Figure 11. Number of articles across publication year by experimental design Control-Intervention (CI) designs and CI combined with time-series data were the most frequently used across all study durations (Figure 12). Beyond one year, the number of studies decreases significantly, with only a few extending beyond 50 months. Longer-term studies predominantly used CI + time series designs, with other designs such as Before-After Control-Impact (BACI) + time series also present. Figure 12. Articles using different study periods (total months) by experimental design. Note: Axis compression at a ratio of 2:1 above 50 months on the x-axis. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 32 www.biodiversa.eu Figure 18. Study biomes by subject, showing the number of articles including both. Coloured bands in the x-axis indicate related but mutually exclusive categories: For these categories, the finest level provided is displayed. Orange = vegetation groups. Blue = invertebrate groups. Purple = vertebrate groups. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 33 www.biodiversa.eu Figure 19. Study biomes and experimental designs used across articles. The highest number of studies with CI + timeseries design (66) were conducted in the tropical-subtropical forest biome followed by savannas and grasslands biome (36) and temperate-boreal forest biome (32) (Figure 19). Studies with BACI + timeseries design were most common in the tropical-subtropical and temperate-boreal forest biomes (9 and 8 studies respectively) followed by intensive land use biome (6). Across all sampling methods, Africa had the highest number of studies, except for those employing Geographical Information System (GIS) methods and third-party databases (Figure 20). GIS-based How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 34 www.biodiversa.eu methods were the most frequently used, and most applied in Asia (25), Africa (19), followed by Central and South America (16 each). GIS, point counts, and stratified sampling were the most widely represented methods across continents, although none was represented in all continents. The highest number of studies using sampling plots were conducted in Africa (22), followed by Europe (13) and South America (7). Stratified sampling was primarily conducted in Africa (12), Asia (10) and Europe (8). Transect-based methods were mostly used in Africa (11), with fewer studies conducted in Asia (6) and Europe (6). Figure 20. Sampling methods used across continents in included articles. SSA = Sub-Saharan Africa. MENA = Middle East and North Africa. Multiple = more than one continent. GIS methods were the most frequently used across all experimental designs, particularly in studies employing Control-Intervention (CI) designs combined with time series (57), followed by BACI + time series studies (17) (Figure 21). Sampling plots were also widely applied, with the highest numbers observed in CI and CI + time series (30 and 23, respectively). CI and CI + time series were the most frequent designs across all sampling methods, with CI + time series being the only design represented across all sampling methods. GPS collars was the least utilised method, and along with mark-recapture were the only methods without CI studies. Only four studies used a Before-After (BA) design, and were How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 35 www.biodiversa.eu based on GIS (2), sampling plots (1), and transects (1). The majority of BACI + time-series utilised GIS (17), followed by point counts (4), stratified sampling (3), and sampling plots (2). The remaining studies employed transects, random sampling, and mark-recapture (1 study each). In contrast, BACI studies without a time-series component used sampling plots (2), GIS, point counts, mark-recapture, and transects (1 study each). Figure 21. Sampling methods and experimental designs used across included articles. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 36 www.biodiversa.eu Satellite measurements were the most applied survey method, particularly for ecosystems (56 studies) and land use (23), followed by vegetation (21) (Figure 22). Direct observation was the only survey method represented in all recorded subjects, with the highest application in woody plants (28), birds (28), and mammals (19). Indirect observation was predominantly used for mammals (21). Some methods, such as kick sampling, quadrat sampling, and pit-trapping were rarely used. Figure 22. Survey methods and subjects used across the included articles. Coloured bands in the x-axis indicate related but mutually exclusive categories: For these categories, the finest level provided is displayed. Orange = vegetation groups. Blue = invertebrate groups. Purple = vertebrate groups. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 37 www.biodiversa.eu Studies conducted at the regional or subnational scale were the most common across many subjects, with notable emphasis on ecosystems (18) and woody plants (17), and vegetation (12) (Figure 23). Localscale studies were also well represented, particularly for mammals (23), birds (14), woody plants (14), and ecosystems (15). National-scale studies were less frequent overall, but still represented across ecosystems (17), mammals (7), and birds (6). Multinational studies focused mainly on ecosystems (14) and land use (8), followed by birds (5). Overall, the scale of study tended to align with the subject, with local and regional studies being most common for field-based and species-focused research, while multinational studies were more prevalent for broad-scale ecological topics like ecosystems and land use. Figure 23. Study scale and subject across included articles. CI and CI + time-series designs were the most frequently applied experimental designs across all subjects (Figure 24). CI + time-series was especially prominent for ecosystems (34), land use (15), and mammals (25). CI alone was widely used in studies on woody plants (20) and mammals (15). BACI + time-series studies were relatively limited but still had notable representation in land use (5), ecosystems (8), and woody plants (3). Time-series designs alone were less common overall but were employed in ecosystems (8) and vegetation (5). BA and BACI designs were rarely used, with only a few studies focused on land use, ecosystems, invertebrates and mammals. Mammals and birds stood out among vertebrates, with CI and CI + time-series being the dominant designs (15 and 25 studies for mammals; 8 and 17 studies for birds). How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 38 www.biodiversa.eu Figure 24. Experimental design and subject used across the included articles. Asia led in number of studies on ecosystems (17), land use (7), and mammals (7). Europe showed notable representation in birds (9), ecosystems (9), and invertebrates (8) (Figure 25). Africa had significant representation in woody plants (13), mammals (12), and ecosystems (8). Central and South America were well-represented for ecosystems (9 studies each), with South America showing additional focus on vegetation (6), mammals (8), and fish (7 studies). North America was less represented overall but included studies on birds (6) and plants (4). MENA had most representation in non-woody (6) and woody (5) plants, while Oceania had limited representation, with just two studies on mammals and single studies on fish, birds, aquatic macroinvertebrates, and ecosystems. Antarctica had no representation for most subjects except for a single study on aquatic plants. Studies considering multiple continents had modest representation, primarily focusing on ecosystems (9) and land use (3). Overall, mammals, ecosystems, and birds were the most studied subjects, with significant contributions from Asia, Europe, and Africa, whereas microorganisms, fungi, and deadwood were sparsely studied across all continents. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 39 www.biodiversa.eu Figure 25. Subjects studied by continent across included articles. Coloured bands in the x-axis indicate related but mutually exclusive categories: For these categories, the finest level provided is displayed. Orange = vegetation groups. Blue = invertebrate groups. Purple = vertebrate groups. The intersections between survey and sampling methods reveal both expected trends and underexplored areas in biodiversity monitoring. Unsurprisingly, satellite measurement was overwhelmingly associated with Geographical Information Systems (GIS) (105 studies). Similarly, direct observation was frequently paired with field-based sampling methods such as sampling plots (52), stratified sampling (32), and systematic sampling (31), which are well-established approaches for species and population assessments. More specialised techniques, such as DNA extraction, and radio or GPS collars, showed limited use and were primarily linked to systematic sampling, indicating their more targeted application in genetic and movement-based studies. Indirect observation demonstrated broader versatility, being applied across all but three survey methods. Methods such as kick sampling, pit-traps, and spring-loaded bar traps were minimally represented. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 40 www.biodiversa.eu Figure 26. Survey method by sampling method for included articles. How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 41 www.biodiversa.eu IUCN category II protected areas were the most frequently studied across all sampling methods, and amongst all IUCN categories, particularly with GIS (44), sampling plots (34), stratified sampling (24), transects (25), and systematic sampling (27) (Figure 27). Overall, GIS was the most widely used method across all PA designations except for UNESCO World Heritage Sites where stratified sampling was more frequent (6 studies, versus 5 using GIS). Studies considering IUCN Categories Ia, Ib, III and IV showed similar patterns, with most relying on GIS, followed by stratified sampling and sampling plots in comparable proportions. Fewer studies looked at IUCN categories V and VI protected areas, considered as multiple-use areas. For these categories, 19 and 14 studies used GIS, respectively, while stratified sampling (5 and 3) and sampling plots (7 and 3) were less commonly applied. Natural 2000 studies predominantly used GIS (5) and sampling plots (5). Studies on UNESCO World Heritage Sites and Biosphere Reserves were represented in similar proportions and employed a comparable range of sampling methods across categories. Studies categorised under Other (e.g., reserves in countries that do not follow IUCN classifications, such as China or South Africa, certain provincial parks, forest reserves, etc.) and Not reported frequently employed GIS (12 and 24, respectively). 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How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 51 www.biodiversa.eu Annex 1. A list of articles to test comprehensiveness of the search string 1. Andam, K. S., Ferraro, P. J., Pfaff, A., Arturo Sanchez-Azofeifa, G., & Robalino, J. A. (2008). Measuring the effectiveness of protected area networks in reducing deforestation. www.pnas.orgcgidoi10.1073pnas.0800437105 2. Carrillo, E., Wong, G., & Cuarón, A. D. (2000). Monitoring Mammal Populations in Costa Rican Protected Areas under Different Hunting Restrictions. In Conservation Biology (Vol. 14, Issue 6). https://www.jstor.org/stable/2641510 3. Gardner, C. J., Jasper, L. D., Eonintsoa, C., Duchene, J. J., & Davies, Z. G. (2016). The impact of natural resource use on bird and reptile communities within multiple-use protected areas: evidence from sub-arid Southern Madagascar. Biodiversity and Conservation, 25(9), 1773–1793. https://doi.org/10.1007/s10531-016-1160-4 4. Graham, V., Geldmann, J., Adams, V. M., Negret, P. J., Sinovas, P., & Chang, H. C. (2021). Southeast Asian protected areas are effective in conserving forest cover and forest carbon stocks compared to unprotected areas. Scientific Reports, 11(1). https://doi.org/10.1038/s41598-021-03188-w 5. Kallimanis, A. S., Touloumis, K., Tzanopoulos, J., Mazaris, A. D., Apostolopoulou, E., Stefanidou, S., Scott, A. v., Potts, S. G., & Pantis, J. D. (2015). Vegetation coverage change in the EU: patterns inside and outside Natura 2000 protected areas. Biodiversity and Conservation, 24(3), 579–591. https://doi.org/10.1007/s10531-014-0837-9 6. Knorn, J., Kuemmerle, T., Radeloff, V. C., Keeton, W. S., Gancz, V., Biriş, I.-A., Svoboda, M., Griffiths, P., Hagatis, A., & Hostert, P. (2013). Continued loss of temperate old-growth forests in the Romanian Carpathians despite an increasing protected area network. Biodiversity Governance in Central and Eastern Europe, 40(2), 182–193. https://doi.org/10.2307/26319125 7. Pfeifer, M., Burgess, N. D., Swetnam, R. D., Platts, P. J., Willcock, S., & Marchant, R. (2012). Protected areas: Mixed success in conserving East Africa’s evergreen forests. PLoS ONE, 7(6). https://doi.org/10.1371/journal.pone.0039337 8. Terraube, J., Gardiner, R., Hohwieler, K., Frère, C. H., & Cristescu, R. H. (2023). Protected area coverage has a positive effect on koala occurrence in Eastern Australia. Biodiversity and Conservation, 32(7), 2495–2511. https://doi.org/10.1007/s10531-023-02615-w 9. Wauchope, H. S., Jones, J. P. G., Geldmann, J., Simmons, B. I., Amano, T., Blanco, D. E., Fuller, R. A., Johnston, A., Langendoen, T., Mundkur, T., Nagy, S., & Sutherland, W. J. (2022). Protected areas have a mixed impact on waterbirds, but management helps. Nature, 605(7908), 103–107. https://doi.org/10.1038/s41586-022-04617-0 How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 52 www.biodiversa.eu Annex 2. Definitions of meta-data values 1. Sampling methodology Transects A straight line that cuts through a natural landscape so that standardised observations and measurements can be made Sampling plots A clearly defined area of land where sampling units for one or more groups of taxa are located and measured Point counts A tally of observations detected by sight and/or sound by a single observer located at a fixed position during a specified period of time Stratified sampling Sampling from divisions across a habitat, which appear as different zones Mark-recapture Used to estimate the size of a population where it is impractical to count every individual. A small number of individuals is captured, marked, released and then recaptured systematically Random sampling Samples selected randomly from the whole area Camera traps Cameras are positioned in a static location and movement triggers recording of a series of images of identifiable species/individuals Geographical Information System Including satellite and aerial imagery Systematic sampling Collecting data in an ordered or regular way, eg every 5 metres or every fifth tree 2. Survey method (outcome measurement) pit-traps A trapping pit for small animals, such as insects, amphibians and reptiles basket traps Traps for freshwater organisms that facilitate entry but prohibit exit (made as baskets) kick sampling A kick net is held against the riverbed with the water flowing into it, whilst upstream of the net, the surveyor kicks the riverbed to disturb and dislodge any invertebrates satellite measurement Satellite or aerial imagery is recorded and used to quantify electromagnetic radiation (visible/non-visible light) sweep netting Sturdy nets, often with a canvas bag, that are used to collect insects and other invertebrates from long grass hand searching Manually turning over leaves or stones to search for organisms direct observation Measuring something by direct line of sight indirect observation Measuring something by using indications of presence (e.g. prints or scat) direct listening Measuring something by listening for calls/noise of presence cast net A fishing net that is thrown out and immediately drawn in again, rather than being set up and left gillnet A static fishing net which is hung vertically so that fish get trapped in it by their gills active fishing Fishing gear that is dragged through the water by human, animal or engine power live trap A terrestrial box used to trap mobile organisms questionnaire An interview survey given to humans How is the effectiveness of terrestrial protected areas to conserve biodiversity measured? 53 www.biodiversa.eu 3. Study type Experimental Something in the environment is directly manipulated by researchers and then measured Observational A system is observed without intentionally being affected in any way 4. Experimental design BACI Before-After-Comparator-Intervention (i.e. at least one control sire measured JUST before and after the intervention happened, i.e. not multiple measurements over time after intervention) BA Before-After - i.e. no more than 2 measurements, one before and one after the intervention was put in place CI Comparator-Intervention - i.e. a control site and an intervention site measured ONLY after the intervention happened (no more than 2 measurements over time, otherwise it is "Time-series") Time-series Time-series - i.e. 3 or more measurements of the intervention taken over time (NO CONTROL sites) CI + time-series Comparator-Intervention and time-series together - i.e. a control and intervention site measured more than 3 times ONLY AFTER the intervention occurred (NO BASELINE) BACI + time-series Before-After-Comparator-Intervention and time series - i.e. baseline measurements before the intervention at a control and an intervention site, measured 3 or more times in total (not just twice, before and after)