Urban biodiversity: State of the science and future directions

Anuran responses to urbanization: evaluating life history traits of Rhinella arenarum in urban wetlands

Wetlands are unique ecological environments capable of harboring high biodiversity. However, urbanization can degrade, eliminate, or transform these habitats. Although amphibians utilize habitats created by humans in urban landscapes, few studies have investigated the influence of the habitat quality on the life history of anurans. We assessed life history traits such as snout-vent length (SVL), body condition, and reproductive investment in the South American common toad Rhinella arenarum, to determine whether urbanization is harmful or beneficial to this species. We sampled wetlands with different levels of urbanization in Río Cuarto city, Córdoba, Argentina. We recorded males with lower SVL in medium urbanized wetlands and those with the highest SVL in both low and high urbanization categories, similar to what was found for body conditions with males with low body conditions inhabiting wetlands with a medium degree of urbanization. In females, lower SVL was recorded in medium urbanization and highest SVL in high and low urbanization. It is observed that females recorded in highly urbanized wetlands have a very low body condition. The reproductive investment parameters were not significantly different, but we observed an association between a greater number of eggs and clutch size with wetlands of low urbanization. These results show a variability of responses of R. arenarum to urbanization, which could be due to phenotypic plasticity in its life history parameters, allowing it to inhabit urban areas. Continuous monitoring of the species in these wetlands is needed to determine if these biological responses are temporary or persistent.

A systematic scoping review reveals that geographic and taxonomic patterns influence the scientific and societal interest in urban soil microbial diversity

Urban green areas provide multiple ecosystem services in cities, mitigating environmental risks and providing a healthier environment for humans. Even if urban ecology has become popular in the last decade, the soil environment with its microbiota, which sustains many other biodiversity layers, remains overlooked. Here, a comprehensive database of scientific papers published in the last 30 years investigating different aspects of soil microbial diversity was built and systematically reviewed. The aim was to identify the taxa, experimental methods and geographical areas that have been investigated, and to highlight gaps in knowledge and research prospects. Our results show that current knowledge on urban soil microbiota remains incomplete, mainly due to the lack of publications on functional aspects, and is biased, in terms of investigated taxa, with most studies focused on Prokaryotes, and geographic representativeness, with the interest focused on a few large cities in the Northern hemisphere. By coupling bibliometrics with statistical modelling we found that soil microbial traits such as biomass and respiration and omics techniques attract the interest of the scientific community while multi-taxa and time-course studies appeal more to the general public.

A systematic review of the associations between biodiversity and children's mental health and wellbeing

There is a growing interest in how exposure to biodiversity influences mental health and wellbeing; however, few studies have focused on children. The aim of this review was to identify studies that used components of biodiversity and children's health outcomes to assess if there were any themes that could be used to inform urban design and understand the mechanisms behind associations. We used a PROSPERO registered protocol to identify eligible studies following pre-defined inclusion criteria. After searching five databases, 25 studies were included in the review. From these articles we extracted data on the biodiversity exposure and mental health and wellbeing outcomes. Five categories of biodiversity exposure were identified, including species diversity (n = 1; 4%), functional diversity (n = 6; 26%), ecological community (n = 9; 36%), green space metrics (n = 4; 16%), and high-level classifications (n = 6; 24%). Children's health and wellbeing were tabulated into seven categories: play (n = 10; 40%), wellbeing (n = 6; 24%), mental health and cognitive functioning (n = 5; 20%), attention deficit hyperactivity disorder (ADHD)-related behaviours (n = 4; 16%), preferences for nature (n = 3; 12%), academic achievement (n = 2; 8%), and restoration (n = 2; 8%). The high heterogeneity of biodiversity and health measures reduced our ability to identify relationships across studies and formally test for an exposure-dose response. Future research that uses standardised and transferable biodiversity measurements at multiple scales, has stronger reporting rigour, greater consideration of potential modifiers, and increased representation of studies from the Majority World are essential for building a stronger evidence base to deliver child-centred biodiverse landscapes.

Do meteorological variables impact air quality differently across urbanization gradients? A case study of Kaohsiung, Taiwan, China

Air pollution has become a major challenge to global urban sustainable development, necessitating urgent solutions. Meteorological variables are key determinants of air quality; however, research on their impact across different urban gradients remains limited, and their mechanisms are largely unexplored. This study investigates the dynamic effects of meteorological variables on air quality under varying levels of urbanization using Kaohsiung City, Taiwan, as a case study. Meteorological and air pollutant data from monitoring stations in Kaohsiung, Taiwan, for the year 2023 were collected and analyzed. The Air Quality Index (AQI) was used to quantify air quality levels, and Granger causality tests and Vector Autoregression (VAR) models were employed to analyze the dynamic relationships between meteorological variables and AQI. The results revealed that: (1) Suburban areas exhibited significantly better air quality than urban and near-urban areas, with annual AQI values of 59.58 in Meinong (outskirts), 67.86 in Renwu (suburbs area), and 76.73 in Qianjin (urban area), showing a progressive improvement in air quality from urban to suburban areas, primarily due to lower levels of urbanization and abundant forest resources; (2) Temperature and relative humidity emerged as key meteorological variables influencing AQI, with Granger causality tests indicating that temperature significantly affects AQI, especially in urban areas. Impulse response analysis revealed that temperature had a notable positive and negative correlation effect on AQI over lagged periods, while wind speed showed a negative correlation with AQI in suburban areas, gradually shifting to a positive correlation over time; (3) Variance decomposition indicated that temperature had the largest impact on AQI in urban areas, particularly with cumulative lag effects, while wind speed was the main variables influencing air quality in suburban areas. This study provides scientific evidence for future urban planning and environmental management, supporting the development of more effective air quality improvement strategies to promote sustainable urban development.

Urbanization Impacts Top Predators and Alters Biotic Interactions in Predator-Prey-Mutualistic Communities of Urban Dry Grasslands

Urbanization as a major driver of global change modifies biodiversity patterns and the abundance and interactions among species or functional species groups. For example, urbanization can negatively impact both predator-prey and mutualistic relationships. However, empirical studies on how urbanization modifies biotic, particularly multitrophic, interactions are still limited. In this study, we applied a framework focused on a predator-prey-mutualistic relationship involving communities of insect-pollinated vascular plants, pollinators (bees and hoverflies), predatory spiders, and sand lizards as top predators to test (i) the effect of urbanization on abundance and species richness at different trophic levels and (ii) the effect of urbanization on the regulation of biotic interactions using correlations between species abundances as a proxy. By assessing 56 dry grassland patches in Berlin, Germany, we found that higher trophic levels (sand lizard abundance as well as predatory spider species richness and abundance) were significantly impacted by urbanization whereas pollinators were affected to a lesser degree (only abundance, but not species richness). In contrast, insect-pollinated vascular plants were not impacted by urbanization. Path analyses revealed significant relationships in low-urbanized areas. In these areas, we observed significant bottom-up-regulated mutualistic and predator-prey interactions (plants-pollinators, and pollinators-predatory spiders), as well as top-down-regulated predator-prey interactions (sand lizards-pollinators, and predatory spiders-pollinators). In contrast, no significant interactions were found in highly urbanized sites. Our results suggest that bottom-up regulation is stronger than top-down regulation in low-urbanized areas. To our knowledge, this is the first study to examine the effects of urbanization on predator-prey-mutualistic interactions and to determine whether these interactions are regulated by bottom-up or top-down processes. These findings enhance our understanding of multitrophic interactions in urban environments and their associated ecosystem services, such as pollination, thereby supporting efforts in urban biodiversity conservation.

Navigating discreetly: Spatial ecology of urban wild boar in Bordeaux City's landscape of fear, France

An exemplary urban adapter, the wild boar (Sus scrofa) has successfully colonized urban ecological niches worldwide. Improvement of strategies for optimal management of urban wild boar need to gather more empirical evidence of their spatial ecology. This study is based on GPS tracking and capture-mark-recapture (CMR) of 10 and 59 wild boar, respectively, captured in Bordeaux Metropolis (France). It shows that wild boar have become urban dwellers, with intra-urban home ranges varying from 1.3 to 64.6 km2 (MCP 100 %) and from 0.5 to 9.6 km2 (KDE 95 %), depending on urban conditions. CMR results confirm the low propensity to move away from urban areas (with a mean distance of 2 km between capture and recapture sites), despite a relatively low one-year survival rate since capture (47.5 %), primarily attributable to removal efforts. Wild boar strongly depended on urban woods, mostly during daytime resting, and highly frequented urban meadows during night foraging. Their use of urban agricultural areas was minimal, but they were mostly monitored following corn and grape harvests. Wild boar mitigated the risk associated with close proximity to humans by: a nocturnal activity (72.2 % of active locations registered from sunset to sunrise), which could also be partially attributed to their sensitivity to heat; a strong use of covered habitats, especially during daytime resting and when close to buildings and roads; and a low mobility during night-time foraging (1974 m average daily distance travelled). Moreover, we demonstrate high inter- and intra-individual variability in the spatio-temporal behaviour of urban wild boar. Finally, we discuss the gap between these results and the narratives surrounding the spatial ecology of urban wild boar. Our results not only confirm the species' ability to adapt to urban environments, but also highlight their behavioural flexibility, underscoring the relevance of significant changes in representations and management activities to mitigate human-urban wild boar conflicts.

Widespread introduced species dominate the urban tree assemblage on the endemic-rich tropical island of São Tomé

The Afrotropics are experiencing some of the fastest urbanisation rates on the planet but the impact of city growth on their rich and unique biodiversity remains understudied, especially compared to natural baselines. Little is also known about how introduced species influence β-diversity in these contexts, and how patterns coincide with native ranges of species. Here we investigated how tree assemblages of the endemic-rich Afrotropical island of São Tomé differed between urban, rural and natural zones. These were primarily characterised by urban greenspaces, shade plantations, and old-growth forests, respectively. Based on 81 transects, we assessed biodiversity metrics of endemic, native and introduced species. Tree abundance and species richness were highest in the natural zone, where the composition was most different from the urban zone. The tree community of the rural zone was the most uneven and had the least variation among transects, representing the lowest β-diversity. The urban zone was dominated by introduced species (57.7%), while the natural zone hosted almost exclusively native species (93.3%), including many endemics (26.1%). The biogeographic realms that species originated from were particularly diverse in the urban zone, with few species from the Afrotropics. In contrast to native and endemic trees, introduced trees were clearly associated with urban and rural expansion, as they were much more abundant and species-rich in these zones than in the natural zone, facilitating biotic homogenisation. These findings highlight how urban and rural environments are affecting the native tree flora of São Tomé, and the need for conservation measures geared towards globally threatened and endemic tree species. Importantly, these require the protection of natural forests, despite the rising land demands for settlements and agriculture. Ultimately, such action to conserve endemic trees will contribute to global efforts to prevent further biodiversity declines.

Urbanization alters the relative importance of local and landscape factors affecting plant communities in the Tokyo megacity

Plant communities are impacted by local factors (related to environmental filtering) and landscape factors (related to dispersal limitation). While many studies have shown that the relative importance of these factors in understanding plant community dynamics due to urbanization, little is known about how they are altered by urbanization-a significant threat to biodiversity. This study evaluates the relative importance of local environmental (local factors), landscape, and spatial (landscape factors) variables that influence plant communities in 34 urban green spaces comprising two different habitats (forests and grasslands) along the urban-rural gradients in the Tokyo megacity, Japan. To continuously assess the relative importance of each factor along the urban-rural gradients, we extracted 1000 landscapes within a certain range that contained several sites. Subsequently, the relative importance of each factor and urbanization rate (proportion of artificial built-up area) were estimated for each landscape. Our study found that the relative importance of both local and landscape factors decreased, while that of local factor for native species in forest habitats and that of landscape factors for native species in grassland habitats increased. Collectively, these findings suggest that city size and habitat characteristics must be considered when predicting changes in plant communities caused by urbanization.

Unveiling the urban colonization of the Asian water monitor (Varanus salvator) across its distribution range using citizen science

Background

This study aims to investigate the urban colonization of the Asian water monitor (Varanus salvator) across its entire range of distribution, addressing the paucity of research on this species in urban ecosystems. The research spans the geographic range of the Asian water monitor, focusing on urbanized areas where the species accumulates more observations (Bangkok, Colombo, Jakarta, Kuala Lumpur and Singapore).

Methods

We conducted a systematic review to comprehensively assess the current knowledge of the species' presence in cities. Additionally, citizen science data from repositories like GBIF (Global Biodiversity Information facility ) were utilized to analyze the distribution patterns of V. salvator in urban environments. To elucidate urban distribution and correct collection biases, observations were weighted by sampling effort, using as a proxy all squamate occurrences available from 2010-2023, including V. salvator.

Results

Despite the widespread presence of the Asian water monitor in numerous cities within its distribution range, the available studies on the topic appear to be scarce. Existing research primarily consists of descriptive reports on diet and behavior. Our findings indicate that V. salvator predominantly colonizes green patches in urban areas, such as parks and small gardens. Larger cities exhibit higher records, potentially due to both permanent populations and increased citizen science reporting.

Conclusions

The Asian water monitor, as the largest lizard with established populations in cities, remains scarcely studied on a broader scale. However, the urban design of each city seems relevant to understand the distribution patterns within each context. Our study highlights the need for further research to explore the ecological and human dimensions associated with the species' presence in urban environments.

Ticks and spirochetes of the genus Borrelia in urban areas of Central-Western Poland

Due to the extensive use of green urban areas as recreation places, city residents are exposed to tick-borne pathogens. The objectives of our study were (i) to determine the occurrence of ticks in urban green areas, focussing on areas used by humans such as parks, schools and kindergartens, and urban forests, and (ii) to assess the prevalence of Borrelia infections in ticks in Zielona Góra, a medium-sized city in western Poland. A total of 161 ticks representing the two species Ixodes ricinus (34 males, 51 females, 30 nymphs) and Dermacentor reticulatus (20 males, 26 females) were collected from 29 of 72 (40.3%) study sites. In total, 26.1% of the ticks (85.7% of I. ricinus and 14.3% of D. reticulatus) yielded DNA of Borrelia. The difference in the infection rate between I. ricinus and D. reticulatus was significant. Among infected ticks, the most frequent spirochete species were B. lusitaniae (50.0%) and B. afzelii (26.2%), followed by B. spielmanii (9.5%), B. valaisiana (7.1%), B. burgdorferi sensu stricto, (4.8%) and B. miyamotoi (2.4%). No co-infections were found. We did not observe a correlation in the occurrence of Borrelia spirochetes in ticks found in individual study sites that differed in terms of habitat type and height of vegetation. Our findings demonstrate that the Borrelia transmission cycles are active within urban habitats, pointing the need for monitoring of tick-borne pathogens in public green areas. They could serve as guidelines for authorities for the proper management of urban green spaces in a way that may limit tick populations and the potential health risks posed by tick-borne pathogens.

Urbanization reduces diversity, simplifies community and filter bird species based on their functional traits in a tropical city

Understanding how organisms are coping with major changes imposed by urban intensification is a complex task. In fact, our understanding of the impacts of urbanization on biodiversity is scarce in the global south compared to the north. In this study, we evaluated how bird communities are affected by impact of urban intensification in a tropical city. Thus, we assessed whether increased urban intensification 1) jeopardizes bird diversity (taking into account taxonomic-TD, phylogenetic-PD, and functional-FD dimensions), 2) drives changes in bird community composition and enables the detection of indicator species of such impact, and 3) leads to changes in bird functional traits linked to reproduction, resource acquisition, and survival. We found that urban intensification has a direct impact on the bird community, reducing all three types of diversity. Communities in areas of greater urban intensity are represented by fewer species, and these species are PD and FD less distinct. In addition, we detected at least ten species of areas of lower urban intensity that proved to be more sensitive to urban intensification. With regard to bird traits, we found no significant responses from reproductive, habitat use and feeding variables. Body weight and tail length were the only variables with significant results, with higher urbanization intensity areas selecting for species with lower weights and longer tails. Given the global biodiversity loss we are observing, this information can guide urban managers and planners in designing urban landscapes to maintain biodiversity in cities.

From urban ecology to urban enquiry: How to build cumulative and context-sensitive understandings

This paper positions urban ecology as increasingly conversant with multiple perspectives and methods for understanding the functions and qualities of diverse cities and urban situations. Despite progress in the field, we need clear pathways for positioning, connecting and synthesising specific knowledge and to make it speak to more systemic questions about cities and the life within them. These pathways need to be able to make use of diverse sources of information to better account for the diverse relations between people, other species and the ecological, social, cultural, economic, technical and increasingly digital structures that they are embedded in. Grounded in a description of the systemic knowledge needed, we propose five complementary and often connected approaches for building cumulative systemic understandings, and a framework for connecting and combining different methods and evidence. The approaches and the framework help position urban ecology and other fields of study as entry points to further advance interdisciplinary synthesis and open up new fields of research.

Using unstructured crowd-sourced data to evaluate urban tolerance of terrestrial native animal species within a California Mega-City

In response to biodiversity loss and biotic community homogenization in urbanized landscapes, there are increasing efforts to conserve and increase biodiversity within urban areas. Accordingly, around the world, previously extirpated species are (re)colonizing and otherwise infiltrating urban landscapes, while other species are disappearing from these landscapes. Tracking the occurrence of traditionally urban intolerant species and loss of traditionally urban tolerant species should be a management goal of urban areas, but we generally lack tools to study this phenomenon. To address this gap, we first used species' occurrences from iNaturalist, a large collaborative dataset of species observations, to calculate an urban association index (UAI) for 967 native animal species that occur in the city of Los Angeles. On average, the occurrence of native species was negatively associated with our composite measure of urban intensity, with the exception of snails and slugs, which instead occur more frequently in areas of increased urban intensity. Next, we assessed 8,348 0.25 x 0.25 mile grids across the City of Los Angeles to determine the average grid-level UAI scores (i.e., a summary of the UAIs present in a grid cell, which we term Community Urban Tolerance Index or CUTI). We found that areas of higher urban intensity host more urban tolerant species, but also that taxonomic groups differ in their aggregate tolerance of urban areas, and that spatial patterns of tolerance vary between groups. The framework established here has been designed to be iteratively reevaluated by city managers of Los Angeles in order to track the progress of initiatives to preserve and encourage urban biodiversity, but can be rescaled to sample different regions within the city or different cities altogether to provide a valuable tool for city managers globally.

Long-term population trends of 48 urban bird species correspond between urban and rural areas

Colonization of urban areas by wild species is a widespread phenomenon investigated from various ecological and evolutionary perspectives, yet long-term population trends of organisms in urban areas remain understudied. To fill this knowledge gap, we used data from a large-scale breeding bird monitoring scheme and computed population trends in 48 urban bird species in urban and rural areas of a central European country, Czechia. In most species, trends were similar in both environments, indicating common drivers and/or connections between urban and rural populations. In species with significant trends, the positive trends prevailed, suggesting good performance of urbanized species. This may result from wildlife-friendly environmental changes in cities, such as the expansion of green areas and the maturing of woody vegetation. In respect to species traits, more positive trends were found in larger species than in smaller species in both habitats, likely due to the recovery of previously depleted populations.

As human societies urbanize, so does ecology; taxonomic, geographic, and other research trends in urban vertebrate ecology

The threat to biodiversity posed by urban expansion is well researched and supported. Since the late 1990s, the field of urban ecology has been expanding along with the developed landscapes it studies. Past reviews have shown unequal publication rates in urban ecology literature for taxonomic groups and research locations. Herein, we explore differences in the publication rate of urban studies by vertebrate groups, but also expand on previous investigations by broadening the scope of the literature searched, exploring trends in subtopics within the urban wildlife literature, identifying geographic patterns of such publications, and comparing the rate at which non-native and threatened and endangered species are studied in urban settings. We used linear and segmented regression to assess publication rates and Fisher's exact tests for comparisons between groups. All vertebrate groups show an increasing proportion of urban studies through time, with urban avian studies accelerating most sharply and herpetofauna appearing to be understudied. Non-native mammals are more studied than non-native birds, and threatened and endangered herpetofauna and mammals are more likely to be studied than threatened and endangered birds in urban areas. The plurality of urban wildlife studies are found in North America, while there is a dearth of studies from Africa, Asia, and South America. Our results can help inform decisions of urban ecologists on how to better fill in knowledge gaps and bring a greater degree of equity into the field.

Local and landscape factors shape alpha and beta trophic interaction diversity in urban gardens

Promoting urban green spaces is an effective strategy to increase biodiversity in cities. However, our understanding of how local and landscape factors influence trophic interactions in these urban contexts remains limited. Here, we sampled cavity-nesting bees and wasps and their natural enemies within 85 urban gardens in Zurich (Switzerland) to identify factors associated with the diversity and dissimilarity of antagonistic interactions in these communities. The proportions of built-up area and urban green area at small landscape scales (50 m radius), as well as the management intensity, sun exposure, plant richness and proportion of agricultural land at the landscape scale (250 m radius), were key drivers of interaction diversity. This increased interaction diversity resulted not only from the higher richness of host and natural enemy species, but also from species participating in more interactions. Furthermore, dissimilarity in community structure and interactions across gardens (beta-diversity) were primarily influenced by differences in built-up areas and urban green areas at the landscape scale, as well as by management intensity. Our study offers crucial insights for urban planning and conservation strategies, supporting sustainability goals by helping to understand the factors that shape insect communities and their trophic interactions in urban gardens.

Urban rooftops near sports pitches provide a safe haven for a declining shorebird

Urbanisation has contributed to a severe decline in biodiversity worldwide. However, urban ecosystems can also play an important role in the conservation of threatened species, including ground-nesting birds such as the Eurasian Oystercatcher (Haematopus ostralegus). While the coastal populations of this shorebird have declined sharply, there is growing evidence that pairs nesting on urban flat roofs have high reproductive success. However, the reasons for rooftop nesting and the species' habitat use in urban areas remain poorly understood. In this study, we investigate the territory selection and foraging behaviour of the Eurasian Oystercatcher in the city of Münster (NW Germany). All nesting sites were located on flat roofs (N = 24), most of which were covered with gravel. Overall, reproductive success was high. This was mainly because the roofs provided protection from mammalian predators, leading to increased nest and chick survival. Moreover, breeding performance in the study area was favoured by the proximity of sports pitches. According to our observations, they provided a large amount of easily accessible prey throughout the breeding season. Overall, our study highlights that the reproductive success of the Eurasian Oystercatcher in urban environments is highly dependent on both safe nesting sites on flat roofs and the availability of suitable foraging habitats. Although our study suggests that breeding in urban areas can be beneficial for the model organism, the species' strong territory fidelity makes it very sensitive to the rapid environmental changes occurring in cities. The value of urban ecosystems for bird conservation should therefore be better integrated into urban planning and management.

Supporting function of vegetation in urban riparian ecological corridors for ground-dwelling faunal diversity in Beijing, China

Rapid global urbanization has resulted in increased biodiversity problems, particularly the loss of ground-dwelling fauna in urban areas. Urban riparian corridors are an important green infrastructure for biodiversity conservation, in which urban vegetation plays an essential role. The influence of urban vegetation on ground-dwelling faunal diversity is poorly understood. In this study, we used camera traps to collect the species, functional and phylogenetic diversity of ground-dwelling fauna in the Wenyu River-North Canal riparian corridor in Beijing, and analyzed the effects of the vegetation structure and plant community composition on the diversity and community composition of ground-dwelling animals. A plant-ground dwelling animal interaction network was also built to investigate the food supply of plants for ground-nesting animals. We found that at the vegetation structure level, the high connectivity within a radius of 2000 m and the homogeneous distribution within a radius of 1000 m of vegetation patches had generally positive effects on ground-dwelling animals, and shrublands exhibited a supportive role for mammals in riparian corridors. At the plant community level, tall herbs were instrumental in increasing the willingness of ground-dwelling animals to stay in and pass through the area. Native plants were the main plant food resource for ground-dwelling animals. Given the significant effects of vegetation on ground-dwelling fauna, we advocate that habitat conservation and food supply for ground-dwelling animals be supported through appropriate plant landscape planning and design strategies in ecological corridors in urban areas in the future.

The city nature challenge: A global citizen science phenomenon contributing to biodiversity knowledge and informing local government practices

The bioblitz phenomenon has recently branched into cities, presenting exciting opportunities for local governments to channel participants' efforts toward local issues. The City Nature Challenge (CNC) is one such initiative that has been quickly taken up by hundreds of municipalities worldwide. Despite high levels of participation, we still lack a framework for evaluating how the CNC contributes to local biodiversity knowledge and to inform local government practices. In the present article, we develop such a tool and present a case study that illustrates its applicability. We demonstrate that the collected records contributed to a better understanding of contemporary, local biodiversity patterns and provide a more realistic representation of understudied groups such as insects and fungi. Importantly, we show that the CNC presented local governments with a cost-effective tool to make informed, evidence-based management and policy decisions, improve education and engagement programs, foster cross-council collaborations, and support a stronger sense of environmental stewardship within the local community.

Convergence and divergence in science and practice of urban and rural forest restoration

Forest restoration has never been higher on policymakers' agendas. Complex and multi-dimensional arrangements across the urban-rural continuum challenge restorationists and require integrative approaches to strengthen environmental protection and increase restoration outcomes. It remains unclear if urban and rural forest restoration are moving towards or away from each other in practice and research, and whether comparing research outcomes can help stakeholders to gain a clearer understanding of the interconnectedness between the two fields. This study aims to identify the challenges and opportunities for enhancing forest restoration in both urban and rural systems by reviewing the scientific evidence, engaging with key stakeholders and using an urban-rural forest restoration framework. Using the Society for Ecological Restoration's International Principles as discussion topics, we highlight aspects of convergence and divergence between the two fields to broaden our understanding of forest restoration and promote integrative management approaches to address future forest conditions. Our findings reveal that urban and rural forest restoration have convergent and divergent aspects. We emphasise the importance of tailoring goals and objectives to specific contexts and the need to design different institutions and incentives based on the social and ecological needs and goals of stakeholders in different regions. Additionally, we discuss the challenges of achieving high levels of ecological restoration and the need to go beyond traditional ecology to plan, implement, monitor, and adaptively manage restored forests. We suggest that rivers and watersheds could serve as a common ground linking rural and urban landscapes and that forest restoration could interact with other environmental protection measures. We note the potential for expanding the creative vision associated with increasing tree-containing environments in cities to generate more diverse and resilient forest restoration outcomes in rural settings. This study underscores the value of integrative management approaches in addressing future forest conditions across the urban-rural continuum. Our framework provides valuable insights for policymakers, researchers, and decision-makers to advance the field of forest restoration and address the challenges of restoration across the urban-rural continuum. The rural-urban interface serves as a convergence point for forest restoration, and both urban and rural fields can benefit from each other's expertise.

Protecting China's major urban bird diversity hotspots

The Kunming-Montreal Global Biodiversity Framework puts forward a new conservation target to enhance urban biodiversity. Cities have a great potential for sustaining biodiversity and nurturing a healthy relationship between people and our nearest nature. It is especially important in developing countries such as China, which has a rich biodiversity and a rapidly growing urban population. Using citizen science data, we show that 48% of the national bird diversity and 42% of its threatened species have been recorded in the top-20 most avian-diverse cities of China. Urban bird diversity hotspots clustered along the eastern coast, indicating the importance of establishing an inter-city conservation network along the East Asian-Australasian Flyway. This urban conservation network would be a starting point to promote social recognition of biodiversity's relational value in a country with a vast population and an increasingly important role in meeting UN's Sustainable Development Goals.

Insects in the city: Determinants of a contained aquatic microecosystem across an urbanized landscape

Cities can have profound impacts on ecosystems, yet our understanding of these impacts is currently limited. First, the effects of the socioeconomic dimensions of human society are often overlooked. Second, correlative analyses are common, limiting our causal understanding of mechanisms. Third, most research has focused on terrestrial systems, ignoring aquatic systems that also provide important ecosystem services. Here we compare the effects of human population density and low-income prevalence on the macroinvertebrate communities and ecosystem processes within water-filled artificial tree holes. We hypothesized that these human demographic variables would affect tree holes in different ways via changes in temperature, water nutrients, and the local tree hole environment. We recruited community scientists across Greater Vancouver (Canada) to provide host trees and tend 50 tree holes over 14 weeks of colonization. We quantified tree hole ecosystems in terms of aquatic invertebrates, litter decomposition, and chlorophyll a (chl a). We compiled potential explanatory variables from field measurements, satellite images, or census databases. Using structural equation models, we showed that invertebrate abundance was affected by low-income prevalence but not human population density. This was driven by cosmopolitan species of Ceratopogonidae (Diptera) with known associations to anthropogenic containers. Invertebrate diversity and abundance were also affected by environmental factors, such as temperature, elevation, water nutrients, litter quantity, and exposure. By contrast, invertebrate biomass, chl a, and litter decomposition were not affected by any measured variables. In summary, this study shows that some urban ecosystems can be largely unaffected by human population density. Our study also demonstrates the potential of using artificial tree holes as a standardized, replicated habitat for studying urbanization. Finally, by combining community science and urban ecology, we were able to involve our local community in this pandemic research pivot.

Mammal Roadkills in Lithuanian Urban Areas: A 15-Year Study

We investigated roadkills in urban areas in Lithuania from 2007 to 2022, including two periods with COVID-19 restrictions on people's movement. We analyzed the proportions of wild and domestic animals in roadkill, annual trends, the predominant species involved, and monthly changes during the restrictions. Urban roads were characterized by a low species diversity of roadkilled mammals, with roe deer (Capreolus capreolus) dominating. Total numbers increased exponentially during the study period. The proportion of domestic animals, 12.2%, significantly exceeded that on non-urban roads in the country. The proportion of domestic animals decreased from over 40% in 2007-2009 to 3.7-5.4% in 2020-2022, while the proportion of wild mammals increased from 36.1-39.6% to 89.9-90.6%, respectively. During the periods of COVID-19 restrictions, the number of roadkills in urban areas was significantly higher than expected based on long-term trends. Compared to 2019, the number of roadkilled roe deer in 2020-2021 almost doubled from 700 to 1281-1325 individuals. These anthropause effects were, however, temporary. The imbalance between the roadkill number and transport intensity might require new mitigation strategies to sustain mammal populations in urban areas, at least through improving driver awareness on the issue.

Urbanization, climate and species traits shape mammal communities from local to continental scales

Human-driven environmental changes shape ecological communities from local to global scales. Within cities, landscape-scale patterns and processes and species characteristics generally drive local-scale wildlife diversity. However, cities differ in their structure, species pools, geographies and histories, calling into question the extent to which these drivers of wildlife diversity are predictive at continental scales. In partnership with the Urban Wildlife Information Network, we used occurrence data from 725 sites located across 20 North American cities and a multi-city, multi-species occupancy modelling approach to evaluate the effects of ecoregional characteristics and mammal species traits on the urbanization-diversity relationship. Among 37 native terrestrial mammal species, regional environmental characteristics and species traits influenced within-city effects of urbanization on species occupancy and community composition. Species occupancy and diversity were most negatively related to urbanization in the warmer, less vegetated cities. Additionally, larger-bodied species were most negatively impacted by urbanization across North America. Our results suggest that shifting climate conditions could worsen the effects of urbanization on native wildlife communities, such that conservation strategies should seek to mitigate the combined effects of a warming and urbanizing world.

Urbanisation generates multiple trait syndromes for terrestrial animal taxa worldwide

Cities can host significant biological diversity. Yet, urbanisation leads to the loss of habitats, species, and functional groups. Understanding how multiple taxa respond to urbanisation globally is essential to promote and conserve biodiversity in cities. Using a dataset encompassing six terrestrial faunal taxa (amphibians, bats, bees, birds, carabid beetles and reptiles) across 379 cities on 6 continents, we show that urbanisation produces taxon-specific changes in trait composition, with traits related to reproductive strategy showing the strongest response. Our findings suggest that urbanisation results in four trait syndromes (mobile generalists, site specialists, central place foragers, and mobile specialists), with resources associated with reproduction and diet likely driving patterns in traits associated with mobility and body size. Functional diversity measures showed varied responses, leading to shifts in trait space likely driven by critical resource distribution and abundance, and taxon-specific trait syndromes. Maximising opportunities to support taxa with different urban trait syndromes should be pivotal in conservation and management programmes within and among cities. This will reduce the likelihood of biotic homogenisation and helps ensure that urban environments have the capacity to respond to future challenges. These actions are critical to reframe the role of cities in global biodiversity loss.

Mediterranean university campuses enhance butterfly (Lepidoptera) and beetle (Coleoptera) diversity

Human population growth is causing an expansion of urban areas, a phenomenon known to deeply impact on the Earth’s biodiversity. Therefore, it is key to understand how to conceal urban development with biodiversity conservation. In this context, university campuses can play an important role as they usually present a large array of different environments and green areas, crucial aspects for promoting urban biodiversity as well as human-nature interactions. Several studies have analyzed the biodiversity of university campuses, however, there are still important taxonomic (e.g., insects) and geographical biases (e.g., Mediterranean hotspot) in our current understanding of these urban areas. Insects are fundamental in many ecosystems as pollinators, prey, pest controllers or decomposers among others. This further increases the need to study this group in the urban context. In this study, we have investigated diurnal Lepidoptera and ground-dwelling Coleoptera in three university campuses and three non-campus areas of the city of Granada (Spain). We used spatial and temporal replicates for each area in order to explore whether university campuses hold higher levels of insect biodiversity (e.g., species richness or common species) than other nearby urban areas. In addition, we investigated the potential influence of several additional predictors on insect diversity such as type of land cover, vegetation origin, management intensity, and distance to the outskirts. Our results suggest that Lepidoptera species and Coleoptera families are more diverse in university campuses than in other urban areas, showing also a positive association with the proportion of bare soil and herbaceous cover. Furthermore, they also seem to be benefited from low vegetation management intensity whereas Coleoptera are favored by native vegetation providing clear management recommendations in order to promote such animal groups in cities. Our study indicates that university campuses are important urban areas to preserve insect biodiversity but also highlights the heterogeneity of response among insect groups.

Resilience of Avian Communities to Urbanization and Climate Change: an Integrative Review

The concept of ecological resilience is widely used to assess how species and ecosystems respond to external stressors but is applied infrequently at the level of the community or to chronic, ongoing disturbances. In this review, we first discuss the concept of ecological resilience and methods for quantifying resilience in ecological studies. We then synthesize existing evidence for the resilience of avian communities to climate change and urbanization, two chronic disturbances that are driving global biodiversity loss, and conclude with recommendations for future directions. We only briefly discuss the theoretical framework behind ecological resilience and species-specific responses to these two major disturbances, because numerous reviews already exist on these topics. Current research suggests strong heterogeneity in the responses and resilience of bird communities to urbanization and climate change, although community disassembly and reassembly is high following both disturbances. To advance our understanding of community resilience to these disturbances, we recommend five areas of future study (1) the development of a standardized, comprehensive community resilience index that incorporates both adaptive capacity and measures of functional diversity, (2) measurement/modeling of both community resistance and recovery in response to disturbance, (3) multi-scale and/or multi-taxa studies that include three-way interactions between plants, animals, and climate, (4) studies that incorporate interactions between disturbances, and (5) increased understanding of interactions between ecological resilience and socio-ecological dynamics. Advancement in these areas will enhance our ability to predict and respond to the rapidly accelerating effects of climate change and urbanization.

Winter thriving: on the role of a boreal city on bird communities

Information on how urban areas affect bird communities during winter in the boreal region is still scarce. With the aim of assessing such role of the urban habitats on over-wintering boreal birds, I focused on a city-wide approach in the city of Lahti (southern Finland) and two nearby forests (as controls). Point count surveys were conducted in 157 sites within the city and 30 in the control forests. In order to achieve comparable sets of data to contrast with the reference forests, I randomly selected five 30 point count sub-samples from the Lahti city-wide survey. Species richness was, in general, higher in the sub-samples from the city of Lahti. Such pattern did not show relationship with the built cover of the studied sites. Bird abundances were 3.3–5.9 times higher in the urban sub-samples when contrasted with the forest ones. Although results of this study are limited to a single city and consider one wintering season, they clearly illustrate the important role of urban systems as habitat for wintering birds in boreal systems.

Interactions of Functional Traits With Native Status and Ecosystem Novelty Explain the Establishment of Plant Species Within Urban Ecosystems: Evidence From Berlin, Germany

A key challenge in urban biodiversity conservation is to understand the drivers that govern the population establishment of different groups of species in different urban ecosystems. Here, we ask whether and to what extent vascular plant species establishment (i.e., the ability to establish self-sustaining populations within a certain time span) is driven by interactions of species functional traits, native status, and the type of ecosystem species occur in, with types of ecosystems distinguished by their degree of ecosystem novelty. To answer this question, we use a dataset of 1,178 vascular plant species occurring in Berlin, Germany that originally had been compiled to substantiate the Berlin Red List of endangered plant species. This dataset classifies native and non-native species into casual and established species based on a minimum of 25 years of expert observation. Whether a species is established or casual is distinguished among four broad types of ecosystems: natural remnant, hybrid, novel immature, and novel mature ecosystems. Moreover, we classify species into those native to Berlin and non-native species (split into archaeophytes and neophytes), and link species to selected functional traits and indicator values. By applying ordinal regression within a Bayesian framework, we show that traits are key drivers of these establishment processes and that the traits that drive species establishment differ across types of ecosystems. While across traits, more established species are present in natural remnants, low canopy height, annual life span, and late end of flowering specifically promote establishment in novel immature ecosystems. In hybrid ecosystems, low canopy height and reproduction by seeds are beneficial traits, with the latter promoting establishment in novel mature ecosystems, too. Traits were less important in predicting species establishment in native as compared to non-native species. All types of ecosystems add to urban biodiversity, and trait analyses refine our knowledge on how they can be supported in doing so on the long term. This can help in sharpening conservation measures.