Cities have long been celebrated as epicenters of human connection, creativity, and cultural exchange. Yet beyond their bustling streets and towering skyscrapers, urban landscapes carve out unique niches that reshape the intricate web of life—affecting not only humans but a multitude of other species as well. As metropolitan sprawl accelerates globally, understanding how urbanization influences the relationships among organisms becomes critical to preserving biodiversity and ensuring the resilience of urban ecosystems. Recent research sheds light on these complex dynamics through an innovative eco-evolutionary framework that conceptualizes cities as sequential filters modulating species presence, co-occurrence, and interaction.
At its core, urbanization constitutes a profound transformation of natural habitats, fragmenting continuous ecosystems into patches steeped in artificial structures, pollution, and altered resource availability. These anthropogenic modifications impose stringent environmental pressures that dictate which organisms can persist. Emerging studies reveal that this initial filter – species presence – hinges on traits such as tolerance to disturbed conditions, mobility, and flexible diets. Urban environments selectively favor generalist species capable of exploiting novel resources, often at the expense of specialists. This shift not only influences the composition of urban biota but also sets the stage for altered ecological networks.
Beyond determining who is present, urbanization impacts the probability of species co-occurring in shared spaces. The spatial configuration of green patches, connectivity of habitats, and microclimatic variations form a second filtering layer governing temporal and spatial overlap among species. For instance, fragmented tree canopies and isolated parks may support only a subset of the native fauna, concentrating species interactions into smaller, more frequent encounters yet with reduced diversity. Conversely, novel assemblages may emerge as exotic species infiltrate and animals adapt to urban niches, creating untested ecological communities with unpredictable dynamics.
Crucially, the relationships themselves – the third filter – are transformed under urban influence. Interactions that define ecosystems, such as predation, competition, mutualism, and parasitism, can be weakened, intensified, or redirected. Urban settings modify species behavior and population densities, which in turn alter the strength and nature of these interactions. For example, predator-prey dynamics may be disrupted by changes in predator hunting efficiency amidst human structures or availability of alternative prey. Similarly, pollination networks might collapse or rewire due to declines in specialist pollinators and proliferation of generalist insects.
This framework, which parses urban ecosystems into discrete filters, offers a powerful lens to ask nuanced questions about eco-evolutionary processes in cities. It encourages integrative studies that transcend traditional species inventories to incorporate interactions and evolutionary trajectories affected by urban stressors. These insights are vital because altered interactions cascade through ecosystems, influencing community stability, functional diversity, and ecosystem services that humans rely upon, from pest control to pollination.
Recent empirical evidence highlights dramatic consequences of urbanization on species interactions across diverse taxa. For example, bird communities in metropolitan areas often exhibit increased nesting competition but decreased predator diversity, disrupting trophic cascades. In insect assemblages, urban warming modifies phenology and interaction timings, potentially leading to mismatches between pollinators and flowering plants. Similarly, mammalian carnivores may shift diets toward human refuse, thereby altering food webs and disease transmission dynamics.
Moreover, urban environments create evolutionary pressures that drive rapid adaptation in some species, further reshaping interactions. Certain urban-adapted rodents and birds exhibit behavioral plasticity or genetic changes enhancing boldness, dietary range, or reproductive strategies. These evolutionary responses feed back into ecological networks, influencing which interactions are maintained or lost. Recognizing this dynamic interplay between ecology and evolution in the context of urbanization is essential for predicting future biodiversity patterns.
Despite increasing awareness, major knowledge gaps remain. The complexity of urban ecosystems, coupled with methodological challenges in measuring interactions, limits comprehensive understanding. Many studies focus on presence-absence data or population trends without integrating interaction networks or evolutionary parameters. Additionally, the heterogeneity of urban landscapes—varying with culture, geography, and urban planning—complicates generalizations and demands tailored investigations.
Addressing these gaps requires a multidisciplinary approach blending field observations, experimental manipulations, and advanced modeling techniques. For instance, network analysis can elucidate how urban filters reshape interaction webs, while genomic tools may uncover evolutionary shifts linked to urban stressors. Citizen science initiatives could also contribute valuable large-scale data across urban gradients, capturing temporal and spatial variation in species interactions.
From a practical perspective, this framework has profound implications for urban conservation and management strategies. By identifying critical filters and their effects, urban planners can design green spaces that enhance species co-occurrence and facilitate beneficial interactions, such as pollination or pest regulation. Maintaining connectivity between habitat patches may mitigate fragmentation’s negative effects, enabling species to persist and interact more naturally. Furthermore, managing anthropogenic stressors, including pollution and invasive species, can help preserve native interaction networks.
Incorporating eco-evolutionary principles into urban policy promotes resilient urban ecosystems that support both biodiversity and human well-being. Urban environments can transform from ecological deserts into thriving habitats providing multiple ecosystem services. For example, sustaining pollinator networks enhances urban agriculture and green space vitality, while preserving predator-prey balances helps control disease vectors and crop pests. Recognizing these interdependencies elevates the importance of urban biodiversity beyond aesthetic or recreational value to a cornerstone of sustainable city living.
Interdisciplinary collaborations between ecologists, evolutionary biologists, urban planners, and social scientists can foster integrative solutions. Awareness campaigns highlighting the hidden intricacies of urban ecosystems may engage citizens in stewardship, driving community-based conservation actions. Ultimately, cities represent critical arenas where human development and nature converge, demanding innovative frameworks to understand and harmonize their coexistence.
The urban eco-evolutionary filters framework marks a paradigm shift in conceptualizing urban biodiversity as a dynamic, multi-layered phenomenon shaped by presence, co-occurrence, and interaction filters. This perspective guides future research to move beyond static species lists and unravel the mechanisms shaping biodiversity patterns and ecosystem functions in rapidly transforming cityscapes. By unveiling the complexity of species relationships in urban settings, it sets the foundation for evidence-based practices enabling cities to nurture rich, resilient ecological networks.
As humanity’s urban footprint expands, deciphering the ecological and evolutionary consequences of urbanization transcends academic curiosity – it becomes imperative for sustaining life courses intertwined with urban nature. The cascading effects on species interactions underscore the urgency to rethink biodiversity conservation in cities, integrating ecological intricacies into urban design. Harnessing this knowledge offers hope for cities to become not only centers of human ingenuity but also bastions of coexistence with the natural world.
In conclusion, the interplay between urbanization and species interactions unveils a multifaceted challenge and opportunity. Conceptualizing cities through eco-evolutionary filters enhances scientific understanding while informing pragmatic interventions. This holistic framework paves the way for urban environments that do more than accommodate human needs – they actively foster ecological richness and evolutionary potential, embracing biodiversity as a pillar of sustainable futures.
Subject of Research: The impact of urbanization on species interactions through eco-evolutionary filters encompassing species presence, co-occurrence, and ecological relationships.
Article Title: The effects of urbanization on species interactions.
Article References:
Moreno-García, P., Savage, A., Salgado, A.L. et al. The effects of urbanization on species interactions.
Nat Cities (2025). https://doi.org/10.1038/s44284-025-00288-w
Image Credits: AI Generated
