Segregation’s Ecological Legacy: How Divided Cities Face Unequal Floods, Heat and Green Space

A new special feature published in the Proceedings of the National Academy of Sciences argues that one of the most powerful forces shaping the environments of modern cities is also one of the least examined by ecologists: segregation. Organized by urban ecologist Steward Pickett, a scientist emeritus at the Cary Institute of Ecosystem Studies, together with Cary Research Fellow and New York University professor Timon McPhearson, the collection titled Segregation and Urban Ecology brings together an introductory paper and seven studies that trace how the social sorting of urban populations leaves deep ecological legacies. These legacies determine who lives near landfills and polluting facilities, who enjoys access to parks and tree canopy, who faces the greatest risk from flooding and landslides, and who bears the brunt of extreme heat. The central claim is provocative: segregation is not merely a social phenomenon but a social-ecological system, one that reproduces itself through feedbacks between human decisions and environmental conditions, and one that can, in principle, be disrupted.

The authors make clear that the environmental consequences of segregation are neither subtle nor hypothetical. Segregated communities are more likely to be sited near industrial waste storage, hazardous infrastructure, and similar disamenities, while having less convenient access to the cooling, recreational, and health benefits of urban nature. They are often at greater risk of landslides, flooding, and severe hurricane impacts. Beyond exposure, segregation continues to influence policy and planning around climate adaptation, urban greening, and disaster risk reduction. When these historical legacies are ignored, the papers argue, well-intentioned planning measures can actually worsen existing inequities, for example by channeling green investment into already privileged neighborhoods and triggering displacement. McPhearson stresses the point bluntly for anyone working in urban systems: segregation is a big part of the social, economic, spatial, and power structures of any place where people live, and it cannot be ignored.

Why, then, has ecology been so slow to engage? Pickett suggests the discipline’s traditional focus on measurable biophysical factors has crowded out attention to power. In an ecology class, he notes, students learn about air, water, soils, nutrient cycling, and energy flow, but power differentials driven by race and class, unequal access to wealth-generating opportunities, and other social hierarchies rarely appear on the syllabus. He argues these dynamics belong in ecology textbooks, because if we do not understand how something works, we cannot begin to repair it. Despite a decade or more of scholarship on social and environmental justice, McPhearson adds, researchers in ecology, geography, sustainability, and related disciplines have yet to fully engage with the historical and present-day segregation processes that continue to drive social and ecological life in cities. The special feature is explicitly intended to set a research agenda that corrects this omission.

A foundational paper by J. Morgan Grove and Steward Pickett provides the conceptual scaffolding, using Baltimore, Maryland, to show how ecology can explain why racial inequities persist across generations. The authors demonstrate how zoning decisions, patterns of tree planting, and the siting of undesirable facilities have shaped and reinforced environmental inequalities over decades. Crucially, they frame segregation as a dynamic and resilient social-ecological system, one maintained by time lags and legacies: a zoning map drawn a century ago still influences which neighborhoods have shade, which have impervious surfaces, and which have stormwater capacity, long after the original discriminatory intent has been formally abolished. This systems framing implies that interventions must target the feedbacks that sustain inequity, not merely its visible symptoms, if lasting change is to be achieved.

A second paper, led by Isabelle Anguelovski and colleagues, identifies five interconnected pathways through which marginalized groups are systematically denied ecological benefits while being disproportionately exposed to hazards. These include under-greening, the historical withholding of parks and trees from certain neighborhoods; nature dispossession, the removal of communities from valuable green spaces; and green gentrification, in which environmental improvements raise costs and displace the very residents they were meant to serve. The authors argue that degraded environments are both a result and a driver of segregation, reinforcing social exclusion, ecological harm, and disinvestment in a self-perpetuating loop. Their prescription is equally concrete: planning practices that integrate reparations, community-led solutions, and equitable green infrastructure designed with, rather than merely for, affected residents.

The temporal complexity of segregation emerges vividly in a study of Portland, Oregon, by Idowu Ajibade and colleagues, which combines historical redlining maps with modern market forces to track neighborhood change. Neighborhoods that have remained persistently privileged show more tree canopy, less dense development, lower disaster risks, better preventive care, and fewer diseases. Persistently disadvantaged areas face the most severe conditions, including minimal access to nature, aging infrastructure, the highest pollution and hazard exposure, and the worst health outcomes and disability rates. Yet neighborhoods experiencing gentrification and displacement show mixed outcomes, and the study finds that contemporary segregation does not always align with past redlining maps. The lesson is that segregation is dynamic, continually reshaped by market forces, and must be studied as neighborhoods change over time rather than frozen in archival maps.

The feature also extends the framework beyond the United States. Elizabeth Cook of the Cary Institute and colleagues apply the ecology of segregation to Latin America through a case study of Valdivia, Chile, a city of wetlands situated in a biodiversity hotspot where access to and value of green spaces is profoundly inequitable. The team traces three historic drivers: colonization and the displacement of Indigenous Mapuche communities; a 9.5-magnitude earthquake that locked in patterns of segregation; and neoliberal policies from the 1970s Pinochet dictatorship, along with formal and informal development, that continue to shape who can access and manage urban green spaces. To mitigate these entrenched inequalities, the authors call for inclusive urban planning, community-driven approaches, and explicit acknowledgment of Indigenous perspectives, demonstrating that the framework travels across very different political and ecological histories.

Infrastructure and housing emerge as critical mediating layers in two further studies. Pablo Herreros-Cantis, McPhearson, and colleagues examined pluvial flood risk in New York City, expanding most conventional flood analyses, which focus narrowly on direct flooding impacts and demographic exposure, to incorporate social vulnerability and critical infrastructure. They identify multiple locations where high flood exposure and high social vulnerability coincide, underscoring the need for equity-centered climate adaptation in dense urban settings. In Copenhagen, Denmark, a city renowned for social equity, Natalie Gulsrud and colleagues show that climate adaptation policies applied as one-size-fits-all solutions can exacerbate urban injustices: in a stigmatized neighborhood, the costs and risks of stormwater management fall disproportionately on residents of social housing, revealing how even celebrated green cities can reproduce ecological segregation through housing tenure.

Perhaps the most surprising finding concerns not the distribution of nature but the distribution of knowledge about nature. Diego Ellis-Soto and Melissa Chapman analyzed nearly 60 million volunteer science observations across 195 U.S. cities and found consistently lower sampling of plants, animals, and fungi in formerly redlined neighborhoods. Historical redlining, in other words, has produced enduring disparities in biodiversity data itself, creating blind spots that could bias scientific conclusions and conservation decisions. Segregation thus shapes not only ecological conditions on the ground but also the evidence base through which science understands and prioritizes urban ecosystems, adding a methodological dimension to environmental injustice that few researchers had previously quantified.

The ecology of segregation remains a young field, and the editors are candid about how much remains unknown. Among the outstanding questions posed in the feature: where have systems of segregation been broken or replaced, and how; what feedbacks could be shifted to break the vicious cycle and replace it with a more equitable system; and how can ecology as a discipline address segregation more directly and overtly. Pickett notes that much scholarship emphasizes segregation’s social and historical roots while neglecting how it affects ecological contributions to sustainability and environmental justice, and he hopes the feature will spur additional research, innovation, and ultimately practice to expose and dismantle these previously invisible aspects. The stakes, the authors argue, extend beyond academic completeness: understanding cities as social-ecological systems is presented as a prerequisite for building urban environments that are more equitable, more biodiverse, and more resilient for all residents, not only those who are already advantaged.

Subject of Research: The ecology of urban segregation and its effects on environmental risks and benefits in cities

Article Title: New PNAS special feature examines how segregation continues to shape environmental risks and benefits in cities

Article References: New PNAS special feature examines how segregation continues to shape environmental risks and benefits in cities. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: urban ecology, segregation, environmental justice, redlining, green gentrification, flood risk, climate adaptation, biodiversity data, social-ecological systems, urban planning, tree canopy, PNAS