The allergenic potential of green urban areas in the Macaronesian islands: The case of Funchal City (Madeira)

Urban Climate 54 (2024) 101866 Available online 16 March 2024 2212-0955/© 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). The allergenic potential of green urban areas in the Macaronesian islands: The case of Funchal City (Madeira) Irene Camacho a , * , ´ Alvaro Macías-de-la-Rosa b , Roberto Camacho c , Agnieszka GrinnGofro´ n d , Paloma Cari˜ nanos e , f a Madeira University, Faculdade de Ciˆ encias da Vida, Campus Universit´ ario da Penteada, Funchal 9020-105, Portugal b Institute of Parasitology and Biomedicine L´ opez-Neyra (IPBLN), Spanish National Research Council, Ave. del Conocimiento 17, Armilla 18016, Granada, Spain c Madeira University, Escola Superior de Tecnologias e Gest˜ ao, Campus Universit´ ario da Penteada, Funchal 9020-105, Portugal d Institute of Biology, University of Szczecin, Wąska 13 Street, Szczecin 71-415, Poland e Department of Botany, University of Granada, Granada 18071, Spain f Andalusian Institute for Earth System Research (IISTA-CEAMA), University of Granada, Granada 18071, Spain ARTICLE INFO Keywords: Allergenic plants Urban green spaces Allergenic index IUGZA Funchal city ABSTRACT Public gardens are elements that constitute the urban green infrastructure. Such units provide ecosystem services that are becoming a key concern in urban planning strategies. In this survey the allergenic potential of two public gardens in Funchal, a city exhibiting subtropical and Mediterranean climatic features, was assessed. Different allergenic risk scenarios were considered, and the Allergenicity Indexes recalculated. Results show that the Municipal Garden exhibits an I UGZA (Index of Urban Green Zone Allergenicity) of 0,39 and Santa Catarina Park an I UGZA of 0,16, which are considered spaces of moderate and low allergenicity level, respectively. Among the tested scenarios that could aggravate the I UGZA values, the worst would be an extension of the pollen season for all species. This might represent an issue considering the overall trend towards an earlier start and later end of the pollen season from important allergenic plants in Europe. The assessment of the I UGZA should include all plant biotypes of an urban green area in subtropical regions as they allow us to infer more precisely on the real risk population is exposed to. It seems that increasing species diversity can improve the allergenic indexes, but novel invasive species should be studied to assess their allergenicity level. 1. Introduction Currently more than half of the world’s population lives in cities and a considerable proportion is exposed to several allergenic pollen types. The plant cover composing the urban ecosystems may comprise allergenic plants because of unsuitable green space planning (Calaza et al., 2018). Owing to the close relationship between allergenic plants and pollinosis, research about allergenic potential of urban areas has received more attention by the local and scientific communities. Accordingly, most of the surveys have estimated the allergenic * Corresponding author. E-mail addresses: [email protected] (I. Camacho), [email protected] (´ A. Macías-de-la-Rosa), [email protected] (R. Camacho), [email protected] (A. Grinn-Gofro´ n), [email protected] (P. Cari˜ nanos). Contents lists available at ScienceDirect Urban Climate journal homepage: www.elsevier.com/locate/uclim https://doi.org/10.1016/j.uclim.2024.101866 Received 20 July 2023; Received in revised form 5 February 2024; Accepted 9 March 2024 Urban Climate 54 (2024) 101866 2 potential of urban green spaces (Cari˜ nanos et al., 2014; Cari˜ nanos et al., 2016; Kasprzyk et al., 2019; Aerts et al., 2021) and some have provided guidelines to plan hypoallergenic spaces (Cari˜ nanos and Casares-Porcel, 2011; Calaza et al., 2018). Past and recent urban green designs relied mostly on aesthetic and management criteria. As such, abundance and space distribution of plant species in green spaces have been based on their tolerance to urban environmental stresses and adaptation to the local climate. Also, considerations such as easy maintenance, preference for male specimens and plant originality have been deemed preferable (Cari˜ nanos et al., 2014). Consequently, there has been a massive use of some plant species to the detriment of others, giving rise to an overrepresentation of some pollen types in the atmosphere of several cities and regions. Therefore, such design options led to the introduction of species with allergenic potential and subsequent rise of sensitization rates in the exposed population (Cari˜ nanos and Casares-Porcel, 2011). In addition, the presence of specific plant species with allergenic potential, along with chemical and particulate pollutants, has rapidly increased the number of patients with pollinosis in urban areas (Oh, 2022). Despite the overall beneficial effect of urban green spaces on public health, there is a growing body of research on composition, distribution pattern and phenological characteristics of allergenic pollen plants in the urban ecosystems in order to avoid exposure of urban residents and visitors to pollen allergens (Calaza et al., 2018; Kasprzyk et al., 2019). Most studies regarding urban green designs, allergenic risk and ecological services or disservices have been performed in countries with Temperate and Mediterranean climates, whereas they have been scarce in tropical and sub-tropical regions. Fig. 1. – Map location of Funchal, Portugal (top right) and satellite views of Santa Catarina Park (top left) and Municipal Garden (top centre) (Google maps). Schematics of both gardens, with plant beds coloured in green, for Santa Catarina Park (bottom left) and Municipal Garden (bottom right) Source: Quintal, 2007. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) I. Camacho et al. Urban Climate 54 (2024) 101866 3 The present study took place in Madeira, an island influenced by the Temperate and Mediterranean macro-bio-climates (RivasMartínez, 2001). Due to its geographic position, orography and edaphic conditions, Madeira is considered a subtropical region, showing a great variety of microclimates that allowed the introduction of a wide array of plant species from all over the world (Borges et al., 2008). Many of the introduced plants were brought in for their economic importance or as ornamentals for gardens. The island offers many public access gardens of historical and botanical richness and the many gardens and parks of Funchal, the capital city, are no exception. Exotic species such as Acacia spp., Eucalyptus globulus, Pinus pinaster and Pinus radiata can be found surrounding the city nowadays, whereas centuries ago we had a laurel forest. Such changes in the original natural environment may have implications for asthmatic and allergic sufferers (Hanski et al., 2012). In fact, new species introduced into an area are likely to be non-native, and thus, their impacts on allergic and respiratory health in the sensitised population are unknown and can become an important issue (Kasprzyk et al., 2019). Madeira also belongs to Macaronesia, corresponding to one of the most biodiverse regions in Europe (Quintal, 2007). Tropical and subtropical regions typically exhibit specific climate features, high plant productivity and biodiversity levels, but information regarding the allergenic impact of tropical urban forests is still limited, as is their subsequent impact on human well-being (Escobedo et al., 2023). The aim of the present work is to determine the overall allergenic potential of two highly visited public gardens in Funchal, a city with sub-tropical climatic features. In addition, several potential allergenic risk scenarios were considered, and the respective I UGZA calculated. The study shall bring new insights about the allergenic potential of two important green spaces of the region, infer the public health risk to both locals and visitors and, if necessary, propose mitigation strategies regarding urban vegetation management. 2. Material and methods 2.1. Selection of sites and plant species inventory The study took place in Funchal city (N 32◦39.037 ′ , W 16◦54.494 ′ ), the capital of Madeira. Madeira is the largest island of Madeira Archipelago (Fig. 1), located in the Northeast Atlantic Ocean, 850 km Southwest of Portugal and 750 km West of the Northwestern African coast. The island has a total area of 737 km 2 , with a maximum length of 57 km, in an East-West direction, and a maximum width of 23 Km, North-South. The resident population in Funchal is of around 120.000 people, corresponding to the most populous insular city in the country (Direç˜ ao Regional de Estatística da Madeira, 2021; Pordata, 2023). The climate of the Archipelago is largely influenced by the Eastern branch of the Azores anticyclone, especially from Spring to Fall. The mean annual air temperature is 18.7 ◦C, the temperature range is only 6.4 ◦C and August is the hottest month (22.3 ◦C) whereas February is the coolest (15.9 ◦C). The average annual air temperature in the archipelago of Madeira depends markedly on the altitude, decreasing when the altitude increases. On the lowlands of Madeira, below 200 m (North) – 300 m (South) of altitude, the climate is characterized by a long dry season during the summer months and the vegetation is dominated by xerophytic plants. Above those altitudes, the climate is temperate, with both direct and indirect precipitation all year round (as consequence of persistent clouds of orographic origin), thus there is permanent availability of water in the soil for plant development (Quintal, 2007). The landscape morphology where Funchal urban area is located is an amphitheatre of large dimensions, which abruptly rises from sea level to a mountain range that culminates beyond the 1800 m of altitude, creating favourable conditions for a great phytoclimatic diversity (Santos et al., 2004; Quintal, 2007). Funchal boasts 33 public green spaces that present a balance between arboreal taxa (30.7%), shrubby taxa (33.9%) and herbaceous taxa (35.5%) (Quintal, 2007). According to this author, the most frequent families found in all green spaces are: Bignoniaceae, Asteraceae, Poaceae, Lamiaceae, Lauraceae and Fabaceae. Some species belonging to Asteraceae and Poaceae families also occur on the studied gardens and can contribute to the annual pollen integral (APIn) of Funchal (Camacho et al., 2020). On this basis, the regular monitoring of airborne pollen started in Madeira in 2002, by means of a Hirst-type volumetric spore trap located at Madeira University, following well established guidelines. The yearly average APIn in Funchal, defined as the annual sum of daily pollen concentrations, was 2524 during the period 2002–2017 (Camacho et al., 2020). The airborne pollen spectrum is dominated by some important allergenic taxa/pollen types like Urticaceae, Poaceae, Myrtaceae, Cupressaceae, Pinaceae, Plantago, Platanus, Amaranthaceae and Rumex (Camacho et al., 2016). The local population reveal high sensibilization rates to those pollen taxa, namely: Grasses (17.2%), Pellitory/Parietaria (7.5%), Plane/Platanus (5.2%), Pine/Pinus (2.6%), Timothy grass/ Phleum (1.7%) and Goosefoot/Chenopodium (1.7%) (Camacho, 2017). Two of the most visited gardens of Funchal city centre were chosen for this study (Fig. 1): Municipal Garden (N 32◦38.843 ′ , W 16◦54.677 ′ ) was built in 1880 and lies between 18 and 20 m above sea level, it has a total area of 8.300 m 2 , with a built-up area – auditorium, bar, gardeners’ facilities, and toilets – of 880 m 2 , while 2.720 m 2 correspond to sidewalks and the garden area occupies 4.700 m 2 (Quintal, 2007). It is an almost flat garden, sheltered by the surrounding buildings. With an almost quadrangular shape, it has more than two dozen beds, with no defined geometric patterns, separated by wide sidewalks with a floor of small pebbles. In the west, there is a pond with fountains and a stream. Santa Catarina Park (N 32◦38.766 ′ , W 16◦54.865 ′ ) was opened to the public after 1966, being the biggest green space of the city centre, with a total area of 35.200 m 2 . The built-up space includes a chapel, a playground, a bar, and sanitary facilities, totalling 530 m 2 , while 7.720 m 2 correspond to sidewalks. The landscaped area occupies 26.950 m 2 (Quintal, 2007). The altitude ranges from 30 to 10 m and the dominant exposures are to the Southeast and South. The lagoon is one of the structural elements of the park, it has fountains and there is a small island for nesting and resting for swans and ducks in the middle. The parks under study were visited between March and August of 2021 and the data on the number of plants, covered area and I. Camacho et al. Urban Climate 54 (2024) 101866 4 taxonomic identification in each park was recorded in a field registration form. A plant list from a previous study by Quintal (2007) was used to check and update during the field trips. The studied plants were only angiosperms and gymnosperms, being included trees, shrubs, climbing and herbaceous species. Taxa identification was performed according with the botanical nomenclature of Griffits (1994), Carapeto et al. (2021) and Digital Flora of Portugal (https://jb.utad.pt/flora). The native flora of Madeira was identified based on Press and Short (1994) and Quercetea. (2004). Each record included the scientific and family names, the number of specimens (only for trees), the occupied surface area (m 2 ), plant height and geographic origin. In the case of trees, the maximum height was inferred from literature data. 2.2. Species diversity As biodiversity is linked to the resilience of ecosystems, the application of “Santamour rule” was assessed, where no >10% of any species, no >20% of any one genus and no >30% of one family of trees should be planted in urban green areas. A lack of species diversity renders the urban forest more vulnerable to pest outbreaks, diseases, and stress due to climate change (NCC National Capital Commission, 2021). Quantitative data analysis was used to obtain the diversity index and the evenness index (Baliton et al., 2020) for trees and shrubs. The diversity index (H ′ ) (Shannon-Wiener) formula is described in Eq. 1: H ′ =Σ{(ni n)×ln(ni n) } (1) where: ni =Number of individuals of the i-th species; n =Number of individuals of all species. The evenness index (E) was calculated using the following formula: E= H ′ Hmax (2) where: H ′ =Diversity Index; H max =ln S; S =Species richness. The description of each category of both indexes is shown in Table 1. To assess the correlation between the I UGZA and the diversity and evenness indexes, a Pearson correlation test was performed using the Excel® Microsoft® 365. 2.3. Determination of the Allergenicity index To estimate the potential allergenicity of both urban parks, detailed field surveys were conducted, and an inventory of all flowerproducing individuals was performed. A quantitative index, which estimate the allergenicity of urban green spaces in general (I UGZA, Index of Urban Green Zone Allergenicity) developed by Cari˜ nanos et al. (2014) was calculated. The I UGZA considers two types of parameters: the biological ones, assigned to each species, while the biometric parameters estimate their behaviour as a source of allergen emissions, based on crown diameter and height (Table 2). The height of shrubs and herbaceous plants were measured using a metal measuring tape. A list of biological parameters for the most common tree species in Mediterranean cities was consulted (Cari˜ nanos and Marinangeli, 2021). The combination of above-mentioned parameters yields the following formula (Eq. 3): IUGZA =1 PAV x ST x∑k i=1 PAV ×Si x Hi (3) Where PAV =Potential Allergenicity Value for each species, S T =Total surface area of the park in m 2 , k =number of species, S i = Surface area covered by the i-species in m 2 , H i =maximum height reachable by the i-species in meters. PAV is yielded by three variables in the Mediterranean area (Eq. 4, Table 2): PAV =api×spi×dppi(4) being (ap i ) allergenic potential of the i-th species (0, 1, 2, 3 or exceptionally 4 for main local allergens) (sp i ), strategy of pollination of the i-th species (0,1,2,3), (dppi) duration of the principal pollination period of the i-th species in weeks (1–3) (Cari˜ nanos et al., 2014; Cari˜ nanos et al., 2017; Cari˜ nanos et al., 2019; Cari˜ nanos and Marinangeli, 2021). The combination of these parameters gives a potential allergenicity value for each species in a green space, ranging from 0 (for species scoring 0 for each parameter) to a maximum of 27, or even 36, if the species is considered a major local allergen. PAVs assigned to each plant species and their allergenicity is categorized as nil (0), low (1–6), moderate (8–12), high (16–24) or very high (27–36) (Cari˜ nanos et al., 2014; Cari˜ nanos et al., 2016; Carinanos et al., 2016). Table 1 Classification of Diversity Index (H ′ ) and (E) values. H ′ Description E Description <1 Low diversity, low stability of community (E) value close to 1 The species are evenly distributed 1–3 Moderate diversity, moderate spread number of individual of each species, moderate stability of community >3 High diversity, high spread number of individual of each species, high stability of community (E) value is close to 0 The species are uneven I. Camacho et al. Urban Climate 54 (2024) 101866 5 Table 2 - Scale of values for the parameters used for PAV and biometric parameters (Cari˜ nanos et al., 2014). Parameter Additional sources of information PAV Allergenic potential (ap) 0 =non-allergenic (Camacho et al., 2016; Camacho et al., 2020) 1 =low allergenicity 2 =moderate allergenicity 3 =high allergenicity 4 =main local allergens Pollination strategy (sp) 0 =only female-sex individuals Published literature on individual species (Cari˜ nanos et al., 2016; Cari˜ nanos and Marinangeli, 2021) 1 =entomophilous 2 =ampiphilous 3 =anemophilous Duration of the pollination period (dpp) 1 =1–3 weeks Camacho et al., 2016; Camacho et al., 2020) 2 =4–6 weeks 3 ≥6 weeks Biometric parameters Horizontal crown projection (trees/shrubs) Small-diameter: <4 m Medium-diameter: 4–6 m Large-diameter: >6 m Herbs (meadows, rose beds, lawn coverage,…) m 2 of covered surface Height (trees/shrubs) Mean height attained at reproductive maturity depending on local bio climate zone. Simplified scale: 2, 6, 10, 14 m exceptionally 18 m Herbs (turf, grass, lawn,…) H =0.25 m 2 (minimum height when these species are adequately maintained) I. Camacho et al. Urban Climate 54 (2024) 101866 6 The I UGZA is expressed as a ratio which allows comparing an urban green space with a hypothetical area with similar features and maximum allergenicity. Application of the index yields a value between 0 or null allergenicity and 1 or maximum allergenicity, for spaces registering maximum scores in all factors and measured parameters. I UGZA values >0.3 may be considered indicative of high allergenicity (Cari˜ nanos et al., 2014) and the allergy symptom’s triggering threshold in the local population was set to 0.30 (Cari˜ nanos et al., 2017). Accordingly, urban green parks can be classified as parks with low (<0.2), moderate (0.2–0.3) or high allergenicity (>0.3) (Cari˜ nanos et al., 2019). 2.4. Allergenic potential scenarios As the I UGZA represents the year-round allergy risk for a particular site, the index was further calculated considering potential allergic risk scenarios and the prevailing airborne pollen spectrum of Funchal city. In sequence, 10 potential allergy risk scenarios were considered, as shown in Table 3. The main scenarios considered were OT (Only trees), where flowering predominates in winter and spring, as in the case of Cupressaceae, Fabaceae, Pinaceae and Platanaceae; WH (Without Herbaceous plants) includes the genera of weeds of allergenic importance such as Parietaria, Urtica, Plantago, Rumex and also grasses that normally bloom in Funchal city during spring to autumn; and W2 (Without the 2 most prevalent airborne pollen allergens, Urticaceae and Poaceae). PAV 9–36 hypothesises the removal of plants with PAV values equal or higher than 9; Long PS (Long pollen seasons for all species) and Short PS (Short pollen seasons for all species) infers the allergenic risk under oscillating climatic scenarios, that is, in Long PS, the possibility of the rising temperatures inducing a higher pollen production rates, or in the Short PS, corresponds to water stress conditions which induce less pollen production. The Kruskal-Wallis tests, used to determine whether there were significant differences in the obtained I UGZA values and the recalculated index considering the abovementioned scenarios, was performed using Statistica TIBCO Software Inc., (2020), Data Science Workbench, version 14, http://tibco.com. 3. Results 3.1. Floristic characterization of the green spaces In the present survey, the overall allergenic potential of two public gardens in Funchal city was assessed. A total of 173 plant species belonging to 63 different families were recorded in the Municipal Garden, whereas in Santa Catarina Park 210 species were inventoried, corresponding to 68 plant families. Half of the total area of the Municipal Garden corresponds to green area (50,94%), whilst in the other site the green area represents 36,45%. The families with the highest species richness in Municipal Garden were Araceae (14 species), Arecaceae (10) and Fabaceae (10). In turn, the genera with most species were: Dracaena (5 species), Philodendron (5) Crinum (4) and Callistemon with 3 species. In regard to species abundance in Municipal Garden, the tree species with highest number of individuals were Howea forsteriana (12), Cordia myxa (11), Plumeria rubra (9), Nolina recurvata (9) Chorisia speciosa (7), Phoenix roebelinii (7), Agathis robusta (7), Cycas revoluta (6), Tipuana tipu (4), Syagrus romanzoffiana (4), Livistona chinensis (4), Encephalartos transvenosus (4) and with 3 specimens each Jacaranda mimosifolia, Gingko biloba, Kigelia africana, Schefflera actinophylla, and Dracaena erecta. The shrub species with the highest number of individuals were Dracaena deremensis (19), Cordyline fruticosa (16), Agave attenuate and Cordyline terminalis (11) and Brugmansia versicolor (9). The families that presented the highest species richness in the second site, Santa Catarina Park, were Arecaceae (13 species), Fabaceae (11) and Asparagaceae (10). The genera with most species in this park were: Euphorbia (5 species), Ficus (5), Erythrina, Phoenix, and Dracaena with 4 species each, and Araucaria with 3 species. In this second site, the tree species with highest number of individuals were Tipuana tipu and Archontophoenix cunninghamiana with 16 individuals, 14 of Jacaranda mimosifolia and Encephalartos transvenosus, 13 of Agathis robusta, 12 of Cinnamomum camphora and Spathodea campanulata and 10 of Howea forsteriana. Regarding shrubs, Brugmansia versicolor (10), Yucca gloriosa (9), Phormium tenax (8), Cycas revoluta and Eugenia uniflora with 7 specimens were the most abundant. Table 3 – Description of the hypothetical scenarios used to calculate the I UGZA . Hypothetic Scenario Description OT Only trees WH Without Herbaceous plants W2 Without the 2 most prevalent airborne pollen allergens (Urticaceae and Poaceae) PAV 9 Without species with PAVs ≥9 PAV 12 Without species with PAVs ≥12 PAV 18 Without species with PAVs ≥18 PAV 27 Without species with PAVs ≥27 PAV 36 Without species with PAVs =36 Long PS Long pollen seasons for all species Short PS Short pollen seasons for all species I. Camacho et al. Urban Climate 54 (2024) 101866 7 In Municipal Garden, Chlorophytum comosum (Liliaceae) was the species that revealed the highest surface area covered (9.64%), followed by Stenotaphrum secundatum (Poaceae) or lawn (8.89%), Clivia nobilis (Amaryllidaceae) (7,38%), Clerodendrum splendens (Verbenaceae) (3,46%) and Wedelia trilobata (Asteraceae) (2,91%). In turn, Stenotaphrum secundatum (Poaceae), accounted to almost 12.6% of the surface in Santa Catarina Park, followed by Hemerocallis fulva (Hemerocallidaceae) (8,06%), Agave attenuata (Agavaceae) (5,43%), Acalypha wilkesiana (Euphorbiaceae) (4,16%) and Asparagus setaceus (Liliaceae) (4,03%). The representativeness of plant’s biotype was similar on both gardens (Fig. 2), except for climbing plants, which had up to a total of 0.5% in Santa Catarina Park. Plants that occurred as a “Group” totalled 96 species (55,17%) in the Municipal Garden, whereas in Santa Catarina Park there were 113 species (53,80%). For the remaining species on both sites, the total number of individuals ranged between 12 to a single specimen. Almost 38% of the green surface of Municipal Garden is occupied by plant species derived from Africa/South Africa, followed by plants of Asian (18,34%) and South America origin (9,71%) (Fig. 3). In the second site, 94,77% of the green surface is occupied by plant species derived from the African continent, while a remaining fraction (5,23%) is occupied by species from diverse regions and continents. 3.2. Species diversity On both sites, the Santamour rule was observed (Supplementary Table 1), either both for tree species, genera, and families. The number of tree species and genera didn’t surpass 8,5% of the total in either garden, whereas the number of trees belonging to the same family barely reached 23%. According to the H ′ and E values (Table 4) for the Municipal Garden, there is a moderate diversity of tree species, being unevenly distributed in that site, whereas in Santa Catarina Park there is a high diversity of tree and shrub species, being both evenly distributed. 3.3. Allergenic potential assessment The calculation of the I UGZA index revealed a value of 0,39 for the Municipal Garden and 0,16 for Santa Catarina Park, which, in practical terms, corresponds to urban green spaces of moderate and low allergenicity levels respectively. The dependency between the I UGZA values and H ′ and E indexes were further examined using a Pearson’s correlation test, which showed that allergenicity indexes were negatively correlated with the Shannon-Weaver biodiversity score for the Municipal Garden (H ′ ;−0.719, p =0.018) and for Santa Catarina Park (H ′ ;- = − 0.510; p =0.042) (Table 5). A non-significant positive correlation between I UGZA scores and the Evenness Index was found. The relative proportion of plant species assigned to each biometric parameters on both gardens are shown in Table 6. About 93% and 86% of the species from Municipal Garden and Santa Catarina Park, respectively, presented null or low allergenic potential. Between 80% to 82,18% of all species were entomophilous and 84%, on average, showed long pollination periods. Anemophilous plants account 6 to 8% on both sites. The families that contributed most to the I UGZA in Municipal Garden were Gingkoaceae (33,72%), Lauraceae (23%), and Ulmaceae (8,17%) and in Santa Catarina Park were Lauraceae (11,12%), Araucariaceae (7,16%) and Oleaceae (3,84%) (Table 7). In turn, the species that attained the highest PAV values in Municipal Garden were Araucaria columnaris (PAV =18), Gingko biloba (PAV =18), Celtis australis (PAV =12) and Phoenix roebelinii (PAV =12) (Fig. 4). In Santa Catarina Park, the highest PAV values belonged to spontaneous Parietaria judaica (PAV =36), Fraxinus americana (PAV =27), followed by Cortaderia selloana (PAV =18), Araucaria spp. (PAV =18), Cedrus deodara (PAV =18), and Platanus sp. (PAV =18). Phoenix roebelinii, Phoenix sp. and Quercus ilex all attained a PAV of 12. In Municipal Garden, most species with moderate to high PAV occupied surface areas below 25 m 2 , whereas those with moderate Fig. 2. - Proportion of plant biotypes on both green areas under study. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.) I. Camacho et al. Urban Climate 54 (2024) 101866 8 (caption on next page) I. Camacho et al. Urban Climate 54 (2024) 101866 9 PAV, such as Rumex sp. and Alternanthera ficoidea, attained highest areas (Fig. 5). On regards to Santa Catarina Park, it is possible to verify that, in general, plant species with the highest PAV occupied reduced areas compared to those with lowest PAV values. For example, Araucaria columnaris (PAV =18) occupied a total area of 5 m 2 and Parietaria judaica (PAV =36) of 6 m 2 , whilst Alternanthera ficoidea with lower PAV (9) revealed the highest surface area. 3.4. Allergenic potential scenarios The scenario that would aggravate the I UGZA value corresponds to an extended pollen season for all species present in both sites (Long PS) (Fig. 6). The absence of plants belonging to Urticaceae and Poaceae (W2), wouldn’t affect the current index in Municipal Garden, nor those plants with PAVs equal to 36 (Parietaria judaica) in Santa Catarina Park. More, in the latter, the absence of herbaceous plants or even solely the presence of trees, would result in a slight positive effect on the allergenic index. In addition, the scenarios without plants that exhibit PAV values equal or higher than 9 (PAV 9, 12, 18 and 27), would lower the overall indexes. Lastly, the hypothetical scenario of reduction of the pollen season in all species (short PS) in both sites, would result in the highest reduction of the current I UGZA values. The observed differences between the current I UGZA values and each scenario presented are, nevertheless, not statistically significative (Kruskal-Wallis applied to Municipal Garden: p =1,000 and to Santa Catarina Park: p =0,4335) (p >0,05). Fig. 3. – Percentage of surface area occupied by plant species on each garden according to their geographic origin. Table 4 - Diversity index (H ′ ) and Evenness Index (E) obtained to both green sites. Diversity index (H ′ ) Classification Evenness Index (E) Classification Municipal Garden Tree 1,56 Moderate diversity 0,39 The species are unevenly distributed Shrubs 3,25 High diversity 0,84 The species are evenly distributed Santa Catarina Park Tree 4,01 0,93 Shrubs 3,42 0,84 Table 5 Pearson’s correlation coefficients between the I UGZA and the assessed H ′ and E indexes. Index I UGZA (Municipal Garden) p values I UGZA (Santa Catarina Park) p values Diversity (H ′ ) -0.719* 0.018 −0.510* 0.042 Evenness (E) 0.640 0.721 0.340 0.296 * Statistical significance at p ≤0.05. Table 6 – Relative proportion of plant species assigned to each biometric parameters on both gardens. PAV parameter Municipal Garden Santa Catarina Park Number of species % Number of species % Allergenic potential 0 126 72,41 135 64,29 1 36 20,69 46 21,90 2 11 6,32 20 9,52 3 1 0,57 8 3,81 4 0 0,00 1 0,48 174 100 210 100 Pollination strategy 0 1 0,57 1 0,48 1 143 82,18 168 80,00 2 19 10,92 23 10,95 3 11 6,32 18 8,57 174 100 210 100 PPPi 1 6 3,45 10 4,76 2 19 10,92 27 12,86 3 149 85,63 173 82,38 174 100 210 100 I. Camacho et al. Urban Climate 54 (2024) 101866 16 Acknowledgments The authors are grateful to Professor Raimundo Quintal for providing the flora databases of each study site, and to Professor Agnieszka Strzelczak for the help with the statistical analysis. 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