Abstract Urban ecology examines how biodiversity and ecological processes persist in human-modified environments. The Los Angeles River has been transformed by urbanization into a concrete flood control channel with altered flow regimes, degraded water quality, and reduced habitat quality. We used this site to assess how seasonal environmental variation influences aquatic biodiversity in a highly urbanized river. Monthly environmental DNA samples and corresponding water quality data were collected at two sites along the lower Los Angeles River over a six-month period spanning warm and cool seasons. Water quality parameters tested in this study included temperature, pH, dissolved oxygen, turbidity, electrical conductivity, total dissolved solids, oxidation-reduction potential, and inorganic constituents such as nitrate and sulfate. Metabarcoding of environmental DNA samples were done using cytochrome oxidase I primers and processed with the Anacapa Toolkit for taxonomic classification. Results revealed a shift in relative dominance from arthropods in summer to diatoms in fall. Stress-tolerant taxa such as Tubificidae, ostracods, and oligochaetes persisted under warm, low-oxygen conditions, while sensitive taxa like Baetidae (mayflies) were more abundant during cooler periods with elevated dissolved oxygen. The co-occurrence of tolerant and sensitive groups suggests a transitional ecosystem shaped by fluctuating stressors and the heterogeneous nature of urban stream ecosystems. We found that environmental DNA effectively captured seasonal shifts in community structure and provides a valuable tool for monitoring biodiversity in response to environmental change. This work supports ongoing efforts to evaluate restoration outcomes and improve ecological conditions in urban rivers like the Los Angeles River.
Abstract Urban habitat management, including the removal of mature trees, may alter the availability of nesting habitat for cavity-nesters in urban landscapes. Effective retention of suitable nesting habitat requires species-specific data on nest-site requirements, which remain poorly quantified. Using climbing surveys, we compared the characteristics of trees and cavities used by the Endangered Gang-gang Cockatoo (Callocephalon fimbriatum) for nesting, with those of non-nesting trees and cavities in urban Canberra, Australia. We also evaluated the proportion of available cavities that meet the requirements for Gang-gang Cockatoo nesting and evaluated the reliability of ground-based cavity counts as a habitat assessment method. We found that Gang-gang Cockatoos used deeper cavities with larger entrance sizes and floor diameters than most available cavities in the study area, and nesting cavities were more likely to be found in trees with more cavities than non-nesting trees. Approximately 20% of unused cavities met the suitability criteria for Gang-gang Cockatoo nesting; ∼80% of those were located in trees already used for nesting. Ground-based cavity counts were not a reliable method for determining the true number of cavities in trees as they consistently under- or overestimated cavity abundance relative to climbing surveys. These findings reinforce that animals can be highly selective in the cavities they choose to nest in and protecting known nesting trees is essential for maintaining breeding habitat for the Gang-gang Cockatoo. Our results also support the need for evidence-based urban habitat management that moves beyond ground-based assessments of habitat quality toward climbing surveys that accurately characterise both cavity availability and suitability.
Urbanization can have profound impacts on native wildlife leading to changes in wildlife community composition and behavior. However, to date most urban wildlife studies have occurred within larger cities, where wildlife habitat and connectivity are often limited. Thus, it is unclear whether the impacts of urbanization on wildlife observed in these previous studies similarly occur in smaller size cities where urban development and fragmentation may be less pronounced. To address these questions, we focused our efforts on three mid-size cities (range 127 000-202 000 people) in the Southeastern United States: Athens, Georgia, Jackson, Mississippi, and Little Rock, Arkansas. We used one year of camera trap data from each city using a standardized protocol following the Urban Wildlife Information Network, to evaluate how, and at what scale, socioeconomic and habitat characteristics relate to urban wildlife abundance across and within cities. We found that large spatial scales (i.e. 1000 m) best explained the relationship between species diversity and our habitat metrics and small spatial scales (i.e. 500 m) best explained the relationship with socioeconomic characteristics. At these scales, edge density had the greatest negative impact on species diversity similar to larger cities. However, individual differences within mid-size cities, such as wildlife habitat and human density, play a crucial role in shaping wildlife diversity, challenging the common one-size-fits-all approach. Thus, our findings highlight a need for local governments to consider their unique wildlife communities and landscapes when considering how to plan cities that maximize benefits for wildlife and humans.
Given rapid urbanization across the globe, coping with humans is an important aspect of life in the modern world for most animals. Although human presence is often accompanied by human-associated predators such as dogs, the effects of humans and dogs on animal physiology are rarely considered together. Here, we leverage over 4500 measures of fecal glucocorticoid metabolite (FGM) measurements, a biomarker of stress physiology, collected from more than 1200 marked California ground squirrels (Otospermophilus beecheyi) at two sites differing in human activity. Drawing on 12 years of study, we explored the effects of dispersal status, human presence, and dog activity on FGMs in juveniles and adults to uncover the multiple factors contributing to individual and population-level differences in FGMs. Longitudinal data on between-site dispersal revealed site-level effects on FGMs. FGMs decreased after individuals dispersed to the less disturbed site, but generally increased after dispersers moved to the more disturbed site. Detailed cross-sectional data from the more disturbed site further revealed age- and mass-dependent responses to human and dog activity. Whereas dog activity failed to predict juvenile FGMs, juvenile FGMs were highest for individuals trapped in areas with high human activity. In contrast, dogs represented a major stressor for adult animals, but the effects of dogs on adult FGMs were generally shielded by human presence. Together, these findings uncover the complex relationships among anthropogenic factors, stress physiology, and habitat selection over multiple spatial and temporal scales in wild animals living in a human-influenced world.
Abstract Urban expansion and intensified human use of landscapes are reshaping urban ecosystems and the ways people and wildlife share space, often shifting coexistence toward conflict. This scoping review examines how features of the built environment in cities and urbanizing landscapes exacerbate or mitigate human-wildlife conflicts. We systematically searched Scopus and three EBSCOhost databases up to September 2024 and identified 211 peer-reviewed articles that explicitly link human-wildlife conflicts to urban, peri-urban, or infrastructural conditions. Using qualitative content analysis and pairwise co-occurrence (Jaccard similarity) of coded drivers, we map how land-management decisions and physical structures jointly configure encounter risk across urban social-ecological systems. Urban expansion, habitat proximity and intermixing, environmental degradation, transportation infrastructure, and anthropogenic food resources emerge as the most frequently cited conflict drivers. Dominant mitigation strategies include land-use planning, attractant reduction, habitat restoration or creation, physical barriers, buffer zones, and ecological corridors. Synthesizing these patterns, we identify three emerging paradoxes regarding greening, connectivity, and resources. From these insights, we propose three recurrent architectures of encounter: hard-edge interfaces between settlements and habitats, porous corridor configurations along linear infrastructures, and embedded or nodal architectures where buildings, waste systems, and abandoned spaces concentrate resources. This typology translates ecological evidence on conflict drivers and mitigation into design decisions for urban edges, corridors, and nodes. We argue that human-wildlife conflicts in urbanizing regions cluster within these spatial configurations, which can be diagnosed, monitored, and reworked to support coexistence-oriented urban biodiversity and habitat management.
