Envisioning Ecological Alternatives for Backyards
Read ground-breaking research on cultivating suburban biodiversity
Native Plant Trust has teamed up with the Woodwell Climate Research Center and a group of scientists across the country to report on groundbreaking research into how American homeowners shape the structure and ecology of yard ecosystems.
The Yard Futures Project, a collaboration of scientists affiliated with nine institutions, measured how the structure of yards influences different attributes of residential ecosystems—such as plant and insect biodiversity, microclimates, soil carbon, and potential for nitrogen fertilizer runoff—in the metropolitan areas of Baltimore, Boston, Los Angeles, Miami, Minneapolis-St. Paul, and Phoenix.
The project team contacted homeowners, took measurements in their yards, and conducted homeowner surveys. It classified yards in different ways—sometimes based on demographics, sometimes based on management approaches. The work encompasses both natural and social sciences. It examines not only how homeowners shape their yard ecosystem, but also why they do what they do. The project receives funding from the National Science Foundation's Macrosystems Biology Program, which is investigating the causes and consequences of large-scale ecological patterns.
This blog communicates new findings from this innovative project. It features work done by both established researchers and graduate students, who help to create through their work an emerging science of suburban ecology. The team publishes most of the research in the technical scientific literature, but now joins with Native Plant Trust to make the findings accessible to everyone—so that the results can be put to use creating yards that work for both people and the environment.
The editorial lead for the blog is Christopher Neill, Ph.D., Senior Scientist at Woodwell Climate Research Center in Falmouth, MA. The synthesis at the end of each post is coproduced by Native Plant Trust and the Yard Futures Project.
Current Post: What Determines Which Plants Are Growing in Residential Yards?
By Josep Padullés Cubino
Climate, soils, and topography determine the distribution of natural vegetation across broad areas of the Earth. But in urban areas, those ecological rules might differ—because landscaping practices play outsized roles in shaping plant communities. In residential yards, people also control plant distribution by planting lawns, vegetable gardens, and flower beds. People also reduce environmental stresses by irrigating, fertilizing, and removing weeds. So, if you asked the question, what controls the plant make-up of residential yards, what would be the relative roles of climate and people?
To answer this question, we investigated more than 110 yards in six cities—Baltimore, Boston, Los Angeles, Miami, Minneapolis-St. Paul, and Phoenix. In each yard, we identified all plant species, including those growing in pots, ponds, lawns, or flowerbeds. We also classified them as “cultivated” and “spontaneous." Cultivated species are purposely grown by homeowners, for example, for aesthetic value. Spontaneous species are those that establish themselves without human assistance, often “weeds” such as dandelions, white clover, or crabgrasses. We then tried to explain if the variation in the number of species and the composition of cultivated or spontaneous species in yards depended on the climate, the socioeconomic characteristics of homeowners, and yard size.
We found that climate affected the number of cultivated species less strongly than spontaneous species. This likely reflected the importance of homeowners’ actions, such as adding water, fertilizer, and soil, in creating an appropriate artificial environment in which residents can grow a larger number of species than would otherwise persist under natural conditions. Furthermore, while the number of cultivated plants in yards decreased with more extreme hot and cold temperatures, only extreme hot temperatures constrained the number of spontaneous species. The temperatures in our coldest cites were not extreme enough to limit the number of spontaneous plants.
We also discovered that the number of cultivated species was higher in yards in water-stressed areas than those in areas receiving more summer rainfall. This counterintuitive finding suggests that irrigation largely overcomes natural water limitation, supporting a much larger collection of cultivated species in arid regions than would otherwise be possible. This was even true after accounting for the fact that yards in arid regions had smaller areas of vegetated surface, and thus less potential habitat in which to cultivate plants.
Several studies have indicated that socioeconomic status influences the diversity of plants in yards. This happens because different social and cultural groups cultivate different landscapes based on their preferences and desires. For example, the so-called “luxury effect” describes the tendency of plant diversity in urban greenspace to increase with increasing wealth across neighborhoods or households. In our study, the socioeconomic status of homeowners had no effect on the number of plant species in yards, and very little effect on species composition. Therefore, we concluded that the effect of socioeconomic status on yard plant diversity across the US was largely overwhelmed by the effects of homeowners’ actions and climate. Our study will require more plant surveys in yards across a broader range of socioeconomic brackets to test this idea more thoroughly.
Our study found that climate broadly influences yard vegetation across the US, but people mitigate that effect through the cultivation of plants, irrigation, and other yard management. This also helps us to think about what the future of US yards might look like. As the Earth warms, more and more of the US will experience climates like those now existing in Los Angeles, Phoenix, and Miami. Our work shows that more places will likely need more water to sustain the current levels of diversity—of both spontaneous and cultivated plants—that we now enjoy in yards.
Based on: “Drivers of Plant Species Richness and Phylogenetic Composition in Urban Yards at the Continental Scale.” Josep Padulles Cubino, Jeannine Cavender-Bares, Sarah E. Hobbie, Diane E. Pataki, Meghan L. Avolio, Lindsay E. Darling, Kelli L. Larson, Sharon J. Hall, Peter M. Groffman, Tara L. E. Trammell, Meredith K. Steele, J. Morgan Grove, Christopher Neill. Landscape Ecology: 34, 63–77 (2019).
Summary: A study encompassing six U.S. cities in varied climates examined the relative roles of climate and human management in determining how many plant species—both cultivated and occurring spontaneously—grow in residential yards. The study found that landscaping practices such as planting lawns, vegetable gardens, and flowers play outsized roles in shaping plant communities. People further mitigate the effects of climate by irrigating and taking other management measures. The study also investigated whether the socioeconomic status of homeowners affected the number of plant species in their yards, concluding that socioeconomic factors had little effect. By far, homeowners' actions were the dominant drivers of how many plant species are growing in their yards.
Why it matters: As the Earth warms, more and more of the US will experience hot, dry climates like those now existing in Los Angeles, Phoenix, and Miami—three of the six cities in the study. This research shows that more places will likely need more water to sustain the current levels of diversity—of both spontaneous and cultivated plants—that we now enjoy in yards.
What you can do: Choose native plants that require less water, fertilizer, and other life-support measures than introduced species. As the climate warms, homeowners may need to choose native species adapted to hotter, drier conditions.
In case you've missed any, you can read them here.
Download Post #1: Could We Manage Backyards to Increase Biodiversity?
Download Post #2: Suburban Yards Are Not Deserts! Even (Especially) in the Desert
Download Post #4: What Benefits Do People Want from Their Yards?
Who We Are
Our 25 scientists are based at nine institutions across the country.
The Yard Futures Project is a collaboration of scientists affiliated with institutions from across the U.S., including Woodwell Climate Research Center, Duke University, City University of New York, University of Massachusetts, Johns Hopkins University, University of Minnesota, Arizona State University, U.S. Forest Service, University of Utah, University of Delaware, Portland State University, Davidson College, Clark University, Masaryk University, University of Vermont and Virginia Tech. The research focuses on homeowners and their yards in the metropolitan areas of Boston, Baltimore, Los Angeles, Miami, Minneapolis-St. Paul, and Phoenix and includes on-site field studies, extensive surveys, and interviews. These are the contributing scientists from these institutions:
Christopher Neill, Woods Hole Research Center, studies how changes to land use and climate alter the structure and functioning of ecosystems.
Peter Groffman, City University of New York, investigates nutrient cycling in forests and terrestrial ecosystems. He leads the Yard Futures Project Team.
Christopher Ryan, City University of New York, studies urban ecology, lawns and landscapes, nutrient management, and urban greening, with the goal of increasing biodiversity and improving public health.
Desiree Narango, University of Massachusetts, investigates the ecology and conservation of biodiversity in human-dominated ecosystems such as residential yards, urban forests, and agriculture.
Sarah Hobbie, University of Minnesota, studies the impact of atmospheric changes on the ecosystem and the effects of urbanization and plant species on biogeochemical cycles.
Jeannine Cavender-Bares, University of Minnesota, specializes in physiological ecology, phylogenetics, and linking plant function and evolutionary history to conservation.
Kristen Nelson, University of Minnesota, specializes in environmental sociology, coupled human and natural systems, and sustainable development.
Jesse Engebreston, University of Minnesota, works on interdisciplinary policy implementation and social science research methods for natural resource management.
Sharon Hall, Arizona State University, is an ecosystem scientist who focuses on the ecology of native and managed ecosystems and ecological feedbacks between humans and the environment.
Kelli Larson, Arizona State University, studies attitudes and behaviors relating to residential landscaping practices and wildlife in cities.
Megan Wheeler, Arizona State University, studies the ecological drivers of plant community dynamics in urban residential landscapes.
Susannah Lerman, U.S. Forest Service, studies human management of the urban forest and the health of native bird and insect populations.
Morgan Grove, U.S. Forest Service, investigates the economic and socio-environmental factors that influence urban living.
Dexter Locke, U. S. Forest Service, investigates urban ecology, urban forestry, and spatial data science, with an interest in conducting applied research with urban natural resource managers.
Diane Pataki, University of Utah, studies the human-environment connection around urban vegetation, resource use, and landscape design.
Noortje Grijseels, University of Utah, studies how vegetation such as in green roofs can be used for water managemet in urban areas.
James Heffernan, Duke University, conducts research on ecology and conservation, the urban environment, water, and wetlands.
Tara Trammell, University of Delaware, investigates how urban forests respond to threats such as pollution and invasive species, and how urban forests provide ecosystem services to urban residents.
Jennifer Morse, Portland State University, is an ecosystem ecologist who focuses on the movement of nutrients and the production of greenhouse gases in wetlands, forests, agricultural, and urban ecosystems.
Anika Bratt, Davidson College, studies aquatic ecosystems in urban and agricultural landscapes.
Megan Avolio, Johns Hopkins University, studies the mechanisms by which humans alter plant populations in both grassland and urban ecosystems.
Rinku Roy Chowdhury, Clark University, investigates the diversity of human-environment interactions in forest-agricultural mosaics, urbanizing ecosystems, and coastal mangroves vulnerable to climate change.
Josep Padullés Cubino, Masaryk University, studies ecology, botany, geography, ethnobotany, and urban planning.
Jarlath O'Neil-Dunne, University of Vermont, studies the application of geospatial technology to environmental justice, wildlife habitat mapping, land cover change, and water quality.
Meredith Steele, Virginia Tech, tries to understand cities and their effects on water quality, ecosystem services, and biogeochemical cycles across different regions.