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Urban nature—such as greenness and parks—can alleviate distress and provide space for safe recreation during the COVID-19 pandemic. However, nature is often less available in low-income populations and communities of colour—the same communities hardest hit by COVID-19. In analyses of two datasets, we quantified inequity in greenness and park proximity across all urbanized areas in the United States and linked greenness and park access to COVID-19 case rates for ZIP codes in 17 states. Areas with majority persons of colour had both higher case rates and less greenness. Furthermore, when controlling for sociodemographic variables, an increase of 0.1 in the Normalized Difference Vegetation Index was associated with a 4.1% decrease in COVID-19 incidence rates (95% confidence interval: 0.9–6.8%). Across the United States, block groups with lower income and majority persons of colour are less green and have fewer parks. Our results demonstrate that the communities most impacted by COVID-19 also have the least nature nearby. Given that urban nature is associated with both human health and biodiversity, these results have far-reaching implications both during and beyond the pandemic. Access to green space has been a critical, and contentious, issue for neighbourhood inequality and health outcomes. This Analysis looks at how the COVID-19 pandemic interacts with availability of nature for urban residents.

We hypothesize that lower public visibility of residential backyards reduces households’ desire for social conformity, which alters residential land management and produces differences in ecological composition and function between front and backyards. Using lawn vegetation plots (7 cities) and soil cores (6 cities), we examine plant species richness and evenness and nitrogen cycling of lawns in Boston, Baltimore, Miami, Minneapolis-St. Paul, Phoenix, Los Angeles (LA), and Salt Lake City (SLC). Seven soil nitrogen measures were compared because different irrigation and fertilization practices may vary between front and backyards, which may alter nitrogen cycling in soils. In addition to lawn-only measurements, we collected and analyzed plant species richness for entire yards—cultivated (intentionally planted) and spontaneous (self-regenerating)—for front and backyards in just two cities: LA and SLC. Lawn plant species and soils were not different between front and backyards in our multi-city comparisons. However, entire-yard plant analyses in LA and SLC revealed that frontyards had significantly fewer species than backyards for both cultivated and spontaneous species. These results suggest that there is a need for a more rich and social-ecologically nuanced understanding of potential residential, household behaviors and their ecological consequences.

Urban biotic homogenization is expected to be especially important in residential yards, where similar human preferences and management practices across environmentally heterogeneous regions might lead to the selection of similar plant species, closely related species, and/or species with similar sets of traits. We investigated how different yard management practices determine yard plant diversity and species composition in six cities of the U.S., and tested the extent to which yard management results in more homogeneous taxonomical, phylogenetic, and functional plant communities than the natural areas they replace or than relatively unmanaged areas at the residential-wildland interface (“interstitial” areas). We categorized yards based on fertilizer input frequency and landscaping style: high-input lawns, low-input lawns, and wildlife-certified yards. We defined homogenization as decreased average β-diversity and decreased variance in α-diversity in yards when compared to natural and interstitial areas. We found that all residential yard types regardless of their management were functionally more homogeneous for both α- and β-diversity than the natural and interstitial areas. Nevertheless, wildlife-certified yards were functionally more similar to natural areas than lawn-dominated yard types. All yard types were also more homogeneous in phylogenetic α-diversity compared to natural and interstitial areas, but more heterogenous in taxonomic α-diversity. Within yards, taxonomic, phylogenetic and functional diversity were weakly correlated, highlighting the importance of examining multiple dimensions of biodiversity beyond taxonomic metrics. Our findings underscore the ecological importance of gardening practices that both support biodiversity and create residential plant communities that are functionally heterogeneous.

Residential yards contribute to human well-being and urban biodiversity. The structure, diversity, and composition of yard floras are largely determined by personal choices and landscaping priorities at local scales, but it is unclear whether these relationships hold across broader geographical areas. We investigated the relationship between homeowners’ criteria for vegetation and yard management choices, ecosystem-service based traits, and yard plant diversity (i.e., taxonomic, phylogenetic and functional) in 145 yards distributed across 6 major cities in the U.S. Individual priorities for a set of ecosystem services were collected with closed-ended questions and reduced into four main principal components using factor analyses: natural, neat, showy and low cost. Across cities, priorities for neat yards were negatively related to overall and spontaneous species richness. Priorities for showy yards were positively related to yard aesthetics (based on showiness of flowers, fruits and leaves for component plants) and spontaneous species richness. Homeowners that preferred low-cost yards had a significantly higher proportion of exotics, and yards with significantly lower functional diversity (i.e., a composite measure for plant height, seed mass, and specific leaf area). The proportion of natives was not related to homeowners’ priorities for natural yards and phylogenetic diversity was only weakly and negatively related to priorities for showy yards. Our study corroborates previous research showing that homeowners’ landscaping priorities are only partially related to their yard vegetation at the continental scale. The disconnection might be attributed to broader institutional, structural, and ecological constraints that prevent people’s personal ideals and priorities from being realized.

Creating native-species-rich grasslands to replace agricultural grasslands can be an important strategy for supplementing the area of grasslands, which are in decline in many regions. In the northeastern United States, sandplain grasslands support a diverse plant community and rare plant and animal species that are declining because of reductions in historical disturbances such as fire and grazing. We designed an experiment on Martha's Vineyard, Massachusetts, to test methods of establishing native-species-rich coastal sandplain grassland on former agricultural land. We tested the efficacy of: (1) tilling, herbicide, hot foam, and plastic cover in removing initial nonnative vegetation, and (2) combinations of tilling and seeding for establishing native species. We measured native and nonnative species richness and percent cover before and for 5 years after treatment. Herbicide, plastic cover, and spring, summer, and fall tilling were about equally effective in reducing nonnative species cover and promoting native species cover. Tilling and seeding each increased native species richness and percent cover, and seeding and tilling together increased native species richness and cover more than either treatment alone. Combined seeding and disturbance also reduced the cover of nonnative species, but nonnative species cover remained higher than in adjacent reference sandplain grassland. Results indicated that native species establishment was enhanced by the availability of seeds and by reduction of initial nonnative plant cover. The most efficient method of converting coastal agricultural grasslands to sandplain grassland with a higher number and proportion of native species is a single season of plant removal and seeding.

The decline in species-rich grasslands across the United States has increased the importance of conservation and restoration efforts to preserve the biodiversity supported by these habitats. Abandoned agricultural fields often provide practical locations for the reestablishment of species-rich grasslands. However, these fields often retain legacies of agriculture both in their soils, which may have higher pH and nitrogen (N) contents than soils that were never farmed, and in their plant communities, which are dominated by non-native species and poor in native seed stock. We considered methods of reversing these legacies to create native-species-rich grassland on former agricultural land. We tested seeding and tilling combined with additions of sulfur (S), carbon (C), N or water to establish diverse sandplain grassland vegetation on an old field on Martha's Vineyard, Massachusetts. We measured soil pH, extractable nitrate and ammonium, and total and native species richness and native species cover for 5 years after treatment. S additions lowered pH to values typical of never-tilled sandplain ecosystems and increased native species cover, but had no effect on species richness. C, N, and water additions had no significant effects on the soil or vegetation. Seeding and tilling were more effective at restoring native species richness than any soil amendments and indicated a greater importance of biotic factors compared with soil conditions in promoting sandplain vegetation establishment. S amendment accelerated establishment of native species cover for several years but the effect of S additions compared with seeding and tilling alone declined over time.

Residential lawns are highly managed ecosystems that occur in urbanized landscapes across the United States. Because they are ubiquitous, lawns are good systems in which to study the potential homogenizing effects of urban land use and management together with the continental-scale effects of climate on ecosystem structure and functioning. We hypothesized that similar homeowner preferences and management in residential areas across the United States would lead to low plant species diversity in lawns and relatively homogeneous vegetation across broad geographical regions. We also hypothesized that lawn plant species richness would increase with regional temperature and precipitation due to the presence of spontaneous, weedy vegetation, but would decrease with household income and fertilizer use. To test these predictions, we compared plant species composition and richness in residential lawns in seven U.S. metropolitan regions. We also compared species composition in lawns with understory vegetation in minimally-managed reference areas in each city. As expected, the composition of cultivated turfgrasses was more similar among lawns than among reference areas, but this pattern also held among spontaneous species. Plant species richness and diversity varied more among lawns than among reference areas, and more diverse lawns occurred in metropolitan areas with higher precipitation. Native forb diversity increased with precipitation and decreased with income, driving overall lawn diversity trends with these predictors as well. Our results showed that both management and regional climate shaped lawn species composition, but the overall homogeneity of species regardless of regional context strongly suggested that management was a more important driver. Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate at the National Science Foundation (NSF) [EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, 121238320]; NSF Long-Term Ecological Research Program in Baltimore [DEB 0423476]; Central Arizona-Phoenix [BCS-1026865]; Plum Island (Boston) [OCE-1058747]; Florida Coastal Everglades (Miami) [DBI-0620409]; Cedar Creek [DEB-0620652] We would like to thank all of the homeowners across the country who graciously allowed us access to their properties. This research was supported by the Macrosystems Biology Program in the Emerging Frontiers Division of the Biological Sciences Directorate at the National Science Foundation (NSF) under grants EF-1065548, 1065737, 1065740, 1065741, 1065772, 1065785, 1065831, and 121238320. The work arose from research funded by grants from the NSF Long-Term Ecological Research Program in Baltimore (DEB 0423476), Central Arizona-Phoenix (BCS-1026865), Plum Island (Boston) (OCE-1058747), Florida Coastal Everglades (Miami) (DBI-0620409), and Cedar Creek (Minneapolis-St. Paul) (DEB-0620652). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF. Thanks to the botanical field teams involved in lawn sampling: BAL - Charlie Davis, Dan Dillon, Erin Mellenthin, Charlie Nicholson, Hannah Saunders, Avery Uslaner; BOS - Emma Dixon, Roberta Lombardy, Pamela Polloni, Jehane Semaha, Elisabeth Ward; LA - Aprille Curtis, La'Shaye Ervin; MIA - Bianca Bonilla, Stephen Hodges, Lawrence Lopez, Gabriel Sone; MSP - Chris Buyarksi, Emily Loberg, Alison Slaats, Kelsey Thurow; PHX - Erin Barton, Jenni Learned, Miguel Morgan, Brenton Scott, Dustin Wolkis; SLC Moumita Kundu.