Detecting patterns of vertebrate biodiversity across the multidimensional urban landscape

Beyond the concrete jungle: The value of urban biodiversity for regional conservation efforts

Urbanization deletes and degrades natural ecosystems, contributing to the ongoing biodiversity crisis. Yet, on the local scale, well-managed cities can host significant biodiversity, including endemic and threatened species. Understanding the trade-off between local and regional biodiversity outcomes is limited, primarily due to the lack of comprehensive sampling across heterogeneous urban areas and adjacent regions. To address this knowledge gap and assess urban areas' value for conserving the regional species pool, we conducted an extensive bird survey across an urbanized metropolitan area and its surrounding region (>300 km²). The survey included 11 cities, 24 rural settlements, agricultural areas, and natural habitats, employing high-resolution geographic data (e.g., 3D vegetation layer) to examine land cover effects on α- and β-diversity metrics. Our findings reveal that urban avian diversity can surpass adjacent non-urban areas, with urban green spaces among the most species-rich habitats. Most regional bird species did not avoid urban areas, indicating their significant potential for regional conservation, particularly in human-dominated areas. Across the region, avian communities were highly heterogeneous, driven by species turnover rather than loss, highlighting urban biodiversity complexity. However, factors associated with urbanization negatively affected both α- and β-diversity, with synanthropic species most prevalent in urban habitats. Our findings suggest that strategic urban planning, focusing on compact development and accommodating non-synanthropic species in green spaces, can significantly contribute to regional conservation efforts.

Contemporary Survival Selection Fails to Explain Observed Patterns of Phenotypic Divergence Between Suburban and Forest Populations of the Cuban Endemic Lizard, Anolis homolechis

Although urbanization is a major threat to biodiversity, some native species have managed to persist in urban areas. Populations of such species often show phenotypic differences with their rural counterparts. A crucial question is whether such differences result from different selection regimes between habitats. As previous studies showed that suburban and forest populations of Anolis homolechis differ in both body size and sex ratio, we tested the effect of urbanization on adult survival in those populations based on a long-term capture-marking-recapture survey and replicated design. We assessed the evidence for directional and stabilizing selection on size in two suburban and two forest populations by modeling apparent adult survival and recapture probability separately. Adult survival did not differ between habitat types. In addition, there was no evidence for size-related differential selection on adult survival between habitats. However, irrespective of habitat, we found significant stabilizing selection on female size, whereas male survival was independent of size. Overall, sex had a significant effect on survival independent of habitat type (monthly survival probability: 0.80 for males vs. up to 0.89 for females of optimal size). We discuss our results in relation to the potential mechanisms involved in the observed phenotypic differentiation of A. homolechis and other lizard species in areas transformed by urbanization.

Ecological restoration and biodiversity-friendly management of urban grasslands - A global review on the current state of knowledge

In the face of the global biodiversity decline, ecological restoration measures to actively enhance urban biodiversity and options for biodiversity-friendly greenspace management are high on the agenda of many governments and city administrations. This review aims to summarize and advance the current knowledge on urban grassland restoration by synthesizing research findings on restoration approaches and biodiversity-friendly management measures globally. Indeed, we found restoration approaches to be generally effective in increasing biodiversity; yet, there were variations in the outcomes due to the difference in soil disturbance methods, management regimes, the set of species introduced to a site, and the specific local setting. Based on the reviewed studies, we formulated recommendations for maximizing restoration success of urban grasslands through: i) creating a network of heterogeneous urban greenspaces and enhancing connectivity between them; ii) maintaining the spontaneous vegetation in vacant lots and wasteland sites that can provide habitats for various invertebrate species; iii) evaluating actual soil conditions, soil seed bank, and seed rain before restoration efforts take place since these seed sources could considerably affect the restoration outcomes, iv) preserving nutrient-poor conditions in urban greenspaces instead of introducing nutrient-rich topsoil; v) shifting to less intensive, biodiversity-friendly management in urban greenspaces by reducing mowing frequency and avoiding the use of chemicals; and vi) utilizing native dry grassland species for climate adaptation without irrigation. We further identified knowledge gaps regarding i) city-scale and regional-scale effects of restoration, ii) effects of interventions on multiple taxa and multiple ecosystem services, iii) restoration in small versus mega-cities, and iv) in the global south. These gaps should be addressed in future studies for making general guidelines for urban grassland restoration broadly applicable.

Coping with light pollution in urban environments: Patterns and challenges

Artificial light at night is a growing environmental problem that is especially pronounced in urban environments. Yet, impacts on urban wildlife have received scant attention and patterns and consequences are largely unknown. Here, I present a conceptual framework outlining the challenges species encounter when exposed to urban light pollution and how they may respond through plastic adjustments and genetic adaptation. Light pollution interferes with biological rhythms, influences behaviors, fragments habitats, and alters predation risk and resource abundance, which changes the diversity and spatiotemporal distribution of species and, hence, the structure and function of urban ecosystems. Furthermore, light pollution interacts with other urban disturbances, which can exacerbate negative effects on species. Given the rapid growth of urban areas and light pollution and the importance of healthy urban ecosystems for human wellbeing, more research is needed on the impacts of light pollution on species and the consequences for urban ecosystems.

The effects of cities on quail (Coturnix coturnix) migration: a disturbing story of population connectivity, health, and ecography

The increasing impact of human activities on ecosystems is provoking a profound and dangerous effect, particularly in wildlife. Examining the historical migration patterns of quail (Coturnix coturnix) offers a compelling case study to demonstrate the repercussions of human actions on biodiversity. Urbanization trends, where people gravitate toward mega-urban areas, amplify this effect. The proliferation of artificial urban ecosystems extends its influence across every biome, as human reliance on infrastructure and food sources alters ecological dynamics extensively. We examine European quail migrations pre- and post-World War II and in the present day. Our study concentrates on the Italian peninsula, investigating the historical and contemporary recovery of ringed quail populations. To comprehend changes in quail migration, we utilize trajectory analysis, open statistical data, and linear generalized models. We found that while human population and economic growth have shown a linear increase, quail recovery rates exhibit a U-shaped trajectory, and cereal and legume production displays an inverse U-shaped pattern. Generalized linear models have unveiled the significant influence of several key factors-time periods, cereal and legume production, and human demographics-on quail recovery rates. These factors closely correlate with the levels of urbanization observed across these timeframes. These insights underscore the profound impact of expanding human populations and the rise of mega-urbanization on ecosystem dynamics and services. As our planet becomes more urbanized, the pressure on ecosystems intensifies, highlighting the urgent need for concerted efforts directed toward conserving and revitalizing ecosystem integrity. Simultaneously, manage the needs and demands of burgeoning mega-urban areas. Achieving this balance is pivotal to ensuring sustainable coexistence between urban improvement and the preservation of our natural environment.

Genomic footprints of (pre) colonialism: Population declines in urban and forest túngara frogs coincident with historical human activity

Urbanisation is rapidly altering ecosystems, leading to profound biodiversity loss. To mitigate these effects, we need a better understanding of how urbanisation impacts dispersal and reproduction. Two contrasting population demographic models have been proposed that predict that urbanisation either promotes (facilitation model) or constrains (fragmentation model) gene flow and genetic diversity. Which of these models prevails likely depends on the strength of selection on specific phenotypic traits that influence dispersal, survival, or reproduction. Here, we a priori examined the genomic impact of urbanisation on the Neotropical túngara frog (Engystomops pustulosus), a species known to adapt its reproductive traits to urban selective pressures. Using whole-genome resequencing for multiple urban and forest populations we examined genomic diversity, population connectivity and demographic history. Contrary to both the fragmentation and facilitation models, urban populations did not exhibit substantial changes in genomic diversity or differentiation compared with forest populations, and genomic variation was best explained by geographic distance rather than environmental factors. Adopting an a posteriori approach, we additionally found both urban and forest populations to have undergone population declines. The timing of these declines appears to coincide with extensive human activity around the Panama Canal during the last few centuries rather than recent urbanisation. Our study highlights the long-lasting legacy of past anthropogenic disturbances in the genome and the importance of considering the historical context in urban evolution studies as anthropogenic effects may be extensive and impact nonurban areas on both recent and older timescales.

Cities of the Anthropocene: urban sustainability in an eco-evolutionary perspective

Cities across the globe are driving systemic change in social and ecological systems by accelerating the rates of interactions and intensifying the links between human activities and Earth's ecosystems, thereby expanding the scale and influence of human activities on fundamental processes that sustain life. Increasing evidence shows that cities not only alter biodiversity, they change the genetic makeup of many populations, including animals, plants, fungi and microorganisms. Urban-driven rapid evolution in species traits might have significant effects on socially relevant ecosystem functions such as nutrient cycling, pollination, water and air purification and food production. Despite increasing evidence that cities are causing rapid evolutionary change, current urban sustainability strategies often overlook these dynamics. The dominant perspectives that guide these strategies are essentially static, focusing on preserving biodiversity in its present state or restoring it to pre-urban conditions. This paper provides a systemic overview of the socio-eco-evolutionary transition associated with global urbanization. Using examples of observed changes in species traits that play a significant role in maintaining ecosystem function and resilience, I propose that these evolutionary changes significantly impact urban sustainability. Incorporating an eco-evolutionary perspective into urban sustainability science and planning is crucial for effectively reimagining the cities of the Anthropocene. This article is part of the theme issue 'Evolution and sustainability: gathering the strands for an Anthropocene synthesis'.

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.

Tipping points and interactive effects of chronic human disturbance and acute heat stress on coral diversity

Multiple anthropogenic stressors co-occur ubiquitously in natural ecosystems. However, multiple stressor studies often produce conflicting results, potentially because the nature and direction of stressor interactions depends upon the strength of the underlying stressors. Here, we first examine how coral α- and β-diversities vary across sites spanning a gradient of chronic local anthropogenic stress before and after a prolonged marine heatwave. Developing a multiple stressor framework that encompasses non-discrete stressors, we then examine interactions between the continuous and discrete stressors. We provide evidence of additive effects, antagonistic interactions (with heatwave-driven turnover in coral community composition diminishing as the continuous stressor increased), and tipping points (at which the response of coral Hill-richness to stressors changed from additive to near synergistic). We show that community-level responses to multiple stressors can vary, and even change qualitatively, with stressor intensity, underscoring the importance of examining complex, but realistic continuous stressors to understand stressor interactions and their ecological impacts.

Urban built form shapes avian richness in green spaces

Urban biodiversity plays an important role in ecological processes and ecosystem services within cities, making conservation a priority in many municipal sustainability plans. Urban green spaces (UGS) have been a key strategy for conservation by providing habitat for wildlife, including avian communities. While the ecological attributes necessary to enhance the habitability of UGS for avian communities are relatively well known, an understanding of how variation in the surrounding urban matrix influences avian richness outcomes in these spaces, is less understood. As new urban areas continue to develop and UGS become increasingly important habitat areas, urban designers and planners will need a better understanding of the ways in which urban built form patterns at the matrix-level influence avian biodiversity outcomes at the site-level in UGS. To that end, this study investigates the influence of 4 urban built form matrix-level variables , capturing three-dimensional (3D) configuration patterns, and 6 UGS site-level variables on total avian richness and avian richness by foraging guild using generalized linear model methods in 22 UGS. This analysis was conducted using high resolution land cover data, LiDAR data, and twenty years of bird occurrence data from the eBird community science program in well-surveyed UGS in Los Angeles, California. The size of the UGS was the best predictor of richness patterns across all groups, confirming previous findings. However, several urban form metrics, when included with UGS size, improved model prediction for Carnivores, Insectivores, and Omnivore foraging guilds, indicating that urban built form does influence some avian groups within UGS. The results of this study suggest that the most important factor for avian richness in UGS is the size of the green space, but that urban built form plays a role too, especially when considered from a 3D perspective.