The research, led by Ariel Levi Simons along with Christopher Timlin-Broussard, Avicka Willis, and Jerelyn Lee, tackles one of the most persistent blind spots in urban ecology. Fungi underpin nearly every terrestrial ecosystem, decomposing organic matter, cycling nutrients, forming mycorrhizal partnerships with plants, and even acting as pathogens that shape community structure. Yet despite this ecological centrality, fungi remain chronically understudied in biodiversity monitoring, and their responses to urban stressors have been documented far less thoroughly than those of birds, mammals, or flowering plants. The new study demonstrates that publicly archived community science data can begin to close that gap at a spatial scale no single research project could achieve.

To measure urbanization, the team turned to the National Land Cover Database, which classifies every 30-meter pixel of the continental United States by the fraction of its area covered by surfaces impervious to water flow. This metric serves as a proxy for the hallmark of urban development: sealed ground. When rain cannot infiltrate soil, nutrient flows are disrupted, runoff accelerates, and groundwater recharge plummets. Previous research has shown that surface runoff can double when just 10 to 20 percent of a landscape is paved, and that groundwater recharge in urbanized areas can drop by as much as half. For soil-dwelling organisms, these hydrological upheavals fundamentally alter the resource base on which communities depend.

The fungal observations came from the Global Biodiversity Information Facility, or GBIF, an open archive where community scientists and researchers deposit species records. The researchers extracted every fungal occurrence recorded in California between 2015 and 2024, an initial haul of more than 342,000 records. After filtering to retain only species-level identifications, the dataset still contained nearly 300,000 occurrences, overwhelmingly contributed by human observers. Each record was then assigned to an ecological guild, or trophic mode, using the FUNGuild tool, sorting the fungi into pathotrophs, saprotrophs, and symbiotrophs. Ambiguous assignments and low-confidence classifications were discarded, leaving roughly 180,000 occurrences with clear ecological roles.

Working with opportunistically collected data requires statistical care, because sampling effort varies wildly across space and time. The team addressed this by estimating sample coverage for each putative assemblage, defined as all occurrences within a single imperviousness pixel in a given year and trophic mode, using the iNEXT framework. Only assemblages meeting coverage thresholds of 70, 80, or 90 percent were retained for analysis, a stringent filter that reduced the dataset to between roughly 1,700 and 499 assemblages and about 10,000 occurrences at the strictest threshold. Species richness, the study’s measure of alpha diversity, was then estimated by tracking the asymptotic behavior of richness against sampling effort, with rare species weighted equally to guard against undercounting.

The results paint a nuanced picture. For saprotrophic fungi, the decomposers that break down dead organic matter, estimated richness declined significantly with increasing impervious coverage, though the signal emerged clearly only at the strictest 90 percent coverage threshold. Notably, most of this decline appears to occur as soon as any impervious surface is recorded in the immediate vicinity, suggesting that even modest sealing of the ground may push fungal communities past an ecological threshold. However, when the researchers compared assemblages in areas with and without any impervious cover using nonparametric rank-sum tests, the difference in richness did not reach statistical significance, a reminder of how sensitive such analyses are to sample size and distributional skew. The data were heavily skewed toward unpaved areas, with skewness values rising from 1.64 before filtering to 1.87 after, reflecting a well-documented tendency of community scientists to record species in natural areas rather than city centers.

The more striking and consistent finding concerned beta diversity, the variation in community composition from place to place. For both saprotrophic and symbiotrophic fungi, the dispersion of beta diversity, measured as the average distance of assemblages from a group centroid in Jaccard dissimilarity space, declined significantly with increasing impervious coverage across all coverage thresholds. When assemblages from paved and unpaved areas were compared directly, the declines in dispersion were highly significant, with p-values as low as 10 to the power of negative 15 for saprotrophs and 10 to the power of negative 7 for symbiotrophs. In plain terms, fungal communities in paved landscapes are significantly more similar to one another than those in unsealed habitats, a signature of biotic homogenization. Pathotrophic fungi showed no such pattern, though the authors caution that the small number of recorded occurrences makes it impossible to distinguish a true ecological signal from a statistical artifact.

Why would urbanization flatten the differences between fungal communities? The authors propose ecological filtering as a central mechanism. The mechanical and chemical disturbances associated with development, from soil compaction to heavy metal runoff from roads, impose a narrow set of stresses that only a subset of species can tolerate. Land conversion disrupts the intricate architecture of mycorrhizal networks, while the urban heat-island effect alters temperature and rainfall regimes known to drive fungal richness. Compounding this, urbanization transforms plant communities, replacing native vegetation with a cosmopolitan suite of non-native ornamentals, and each plant community carries its own fungal symbionts. The massive transport of soil that accompanies construction may further homogenize underground communities by mixing propagules across regions. The result is a distinctly urban fungal flora, filtered from a once-diverse regional pool.

The study also underscores both the promise and the pitfalls of community science as a biodiversity monitoring tool. The fungal records were dominated by two phyla, Ascomycota and Basidiomycota, and by saprotrophic and symbiotrophic species, biases that mirror the tendency of amateur mycologists to document mushrooms with conspicuous, easily identified fruiting bodies. Microscopic fungi, aquatic chytrids, and arbuscular mycorrhizal Glomeromycota barely registered. Seasonal fruiting patterns were also obscured by the annual aggregation of records. Yet the sheer volume of data, growing year over year, proved sufficient to test the study’s central hypotheses at the scale of an entire US state, something previously feasible only with intensive DNA-based surveys.

Looking ahead, the authors argue that the era of molecular monitoring is poised to transform fungal conservation. Environmental DNA sampling can resolve species that never produce visible mushrooms, detecting microscopic inhabitants of soil that escape human observation entirely, and fungal datasets are expected to expand rapidly in both volume and taxonomic resolution. As urban land cover continues its global expansion, the California findings offer a warning and a template: the invisible kingdom beneath our feet responds to pavement in measurable ways, and with the right tools, we can now track it. Whether that tracking translates into protection for urban soil communities remains one of the defining ecological challenges of the century ahead.

Subject of Research: Effects of impervious urban surfaces on fungal richness and beta diversity in California

Article Title: Evidence for Reductions in Fungal Richness and Beta Diversity Dispersion Associated With Impervious Surfaces in California

Article References: Simons, A. L., Timlin‐Broussard, C., Willis, A., & Lee, J. (2026). Evidence for Reductions in Fungal Richness and Beta Diversity Dispersion Associated With Impervious Surfaces in California. Ecology and Evolution, 16(10), Article e74448. https://doi.org/10.1002/ece3.74448

Image Credits: AI Generated

DOI: 10.1002/ece3.74448

Keywords: urbanization, fungi, biodiversity, impervious surfaces, community science, GBIF, beta diversity, mycology, California, ecological homogenization, soil ecology, citizen science

The study area was not chosen at random. East Trenton sits in a neighborhood that the U.S. Environmental Protection Agency added to the Superfund National Priorities List in 2025, after investigators determined that soil across the area was contaminated with lead from 19th-century pottery manufacturing plants. Industrial legacies like this are common in older American cities, where factories that once fired glazed ceramics, smelted metals, or processed batteries left behind soils laced with lead that persists for generations. Because lead does not degrade, the contamination deposited more than a century ago remains chemically available at the ground surface today, where it can be picked up on shoes, clothing, pets’ paws, and wind-blown dust and carried directly into living spaces.

The scale of the outdoor contamination documented by the team is striking. Of 242 bare surface soil samples collected from residential properties, 86 percent exceeded the EPA’s residential soil lead hazard level of 200 parts per million, and nearly 94 percent exceeded screening levels designed to flag multiple pathways of lead exposure. Sean Stratton, a recent PhD graduate of the Rutgers School of Public Health and lead author of the study, emphasized that the sampling design made these numbers especially alarming: every sample came from bare soil at the surface, the fraction of the yard most likely to be contacted by children playing outside and most easily tracked indoors on footwear.

The indoor results are what elevate the study from a local soil survey to a finding with national implications. In the 42 homes where interior dust was sampled, 80 percent of floor dust samples exceeded the safety threshold, and this included homes with no interior lead-based paint whatsoever. Perhaps most telling, the researchers found no statistically significant difference in interior floor lead levels between homes with lead-based paint and homes without it. That symmetry points strongly to a shared external source. If paint were the dominant driver of indoor dust lead, homes free of lead paint should have shown markedly lower floor dust concentrations. Instead, the data suggest that outdoor soil, carried across the threshold by ordinary daily activity, is a likely cause of the indoor lead dust burden.

Technically, the investigation relied on a two-stage measurement strategy. Residents were recruited and trained to collect soil samples from 122 homes in the designated area, an approach that dramatically expanded the spatial coverage a conventional academic team could achieve. Researchers then used portable X-ray fluorescence analyzers, instruments that bombard a surface with X-rays and measure the characteristic fluorescent energies emitted by atoms in response, to determine lead-based paint levels on interior surfaces non-destructively. Finally, the team collected settled dust samples from floors, windowsills, and window wells in a subset of 42 homes, allowing them to compare paint lead loading, soil lead concentration, and indoor dust lead within the same properties. This combination of community-collected soil data and instrument-verified interior measurements gave the study both breadth and analytical rigor.

The health stakes could hardly be higher. According to the EPA, lead poisoning can impair brain development in young children, damage vital organs, and cause lasting behavioral and neurological harm. Young children are particularly vulnerable because they play close to the floor, engage in frequent hand-to-mouth activity, and absorb a larger fraction of ingested lead than adults do. A child crawling on a contaminated floor or digging in a contaminated yard can ingest lead dust that produces no immediate visible symptoms while quietly accumulating in developing bones and tissue. Public health agencies have long treated any elevated blood lead level in a child as preventable harm, which is why identifying non-paint sources of indoor exposure matters so much for intervention strategies.

Brian Buckley, director of research with the Rutgers Environmental and Occupational Health Sciences Institute and a co-author of the study, framed the finding as a correction to a widely held rule of thumb. The prevailing assumption, he noted, was that if lead appeared in household dust it must be coming from paint on the walls, and that a house built after 1978 was nothing to worry about. The East Trenton data show that this is not always true. The 1978 ban on consumer lead paint was a landmark public health achievement, but it addressed only one pathway of exposure. In neighborhoods with industrial soil contamination, the calendar age of a house offers little protection, because the hazard arrives from outside rather than from the walls themselves.

The study also stands out as a model of community-engaged environmental science, and that methodology is inseparable from its results. The Rutgers team built on a previous collaboration with the Newark Water Coalition, in which community scientists distributed 500 water testing kits to residents to evaluate whether flushing taps could reduce lead in drinking water. That earlier study, published this year in the Journal of Water & Health, found lead present across surveyed homes and showed that flushing did not eliminate the danger. Just as importantly, the experience established trust between the researchers and affected communities. Residents of East Trenton approached the team to ask for soil testing and granted access to residences that an outside research group might never have been able to enter. Stratton credited that Newark experience with demonstrating the power of citizen-led data collection and empowering residents to help characterize the environmental health threats in their own neighborhood.

The authorship itself reflects that partnership model. Alongside Rutgers researchers including Adrienne Ettinger, chief of staff for research at Rutgers Health, and Zorimar Rivera-Núñez, assistant professor at the Rutgers School of Public Health, the paper lists Shereyl Snider, community organizer for the East Trenton Collaborative, as a co-author. The East Trenton Collaborative, a community organizing and development initiative, works with organizations and public agencies including the New Jersey Department of Environmental Protection and the EPA. Embedding a community organizer in the author team is more than symbolic; it signals that the residents most exposed to the hazard helped generate, interpret, and publish the evidence about it. The research was funded by the National Institutes of Health through grants F31 ES035633, P30 ES05022, and S10 OD010713.

For homeowners, renters, and policymakers, the practical message is that lead risk assessments should look beyond paint. In cities with industrial histories, testing bare soil at the surface, covering exposed dirt with clean soil or mulch, enforcing shoe-removal habits at the door, and wet-cleaning floors and window wells can all reduce the transfer of contaminated particles into living areas, and remediation programs may need to target yards as aggressively as they target walls. For the scientific community, the East Trenton results add urban soil to the short list of exposure pathways that can single-handedly produce hazardous indoor dust. And for the residents of neighborhoods like East Trenton, the study provides something that has historically been denied to communities bearing the burden of industrial contamination: rigorous, peer-reviewed evidence, gathered in their own homes and backyards, documenting the hazard they suspected all along.

Subject of Research: Soil-derived lead contamination contributing to indoor household dust exposure in an urban community

Article Title: Contaminated soil poses hidden lead threat inside homes

Article References: Contaminated soil poses hidden lead threat inside homes. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: lead contamination, soil, indoor dust, community science, Superfund, East Trenton, public health, X-ray fluorescence, lead poisoning, EPA, environmental epidemiology, urban soil