National study reveals urban lawn care habits
March 13, 2014
What do people living in Boston, Baltimore, Miami, Minneapolis-St. Paul, Phoenix, and Los Angeles have in common? From coast to coast, prairie to desert, residential lawns reign.
But beneath this sea of green lies unexpected differences in fertilization and irrigation practices, according to a new study in the Proceedings of the National Academy of Sciences. Understanding urban lawn care is vital to sustainability planning, as more than 80% of Americans now live in cities and suburbs, and these numbers continue to grow.
The study was undertaken to test the "homogenization hypothesis." "Neighborhoods in very different parts of the country look remarkably alike, from lawns and roads to water features,” explains Peter Groffman of the Cary Institute of Ecosystem Studies, a longtime Soil Science Society of America member and one of the paper's authors. "This study is the first to test if urbanization produces similar land management behaviors independent of the local environment."
Some 9,500 residents in the six study cities were queried about their lawn care habits. The research team, led by Colin Polsky of Clark University and colleagues at 10 other institutions, took into account differences in climate and neighborhood socioeconomics, both within and between cities. The team also focused on fertilization and irrigation—practices with potentially hefty environmental price tags.
Fertilizer is rich in nitrogen and phosphorus. These nutrients stimulate lawn growth, but when fertilizer washes into waterways, it causes algal blooms that degrade water quality and rob oxygen from fish and other aquatic life. Landscape irrigation, meanwhile, accounts for nearly one-third of residential water use nationwide, according to the Environmental Protection Agency.
And, in fact, the researchers found that some 79% of surveyed residents watered their lawns and 64% applied fertilizer. "These numbers are important when we bear in mind that lawns cover more land in the United States than any other irrigated crop,” Groffman comments. “What we do in our suburban and urban yards has a big impact, for better or worse, on the environment."
Among the survey's other findings: In Los Angeles, 66 percent of younger residents fertilized their lawns, while 73 percent of older residents did. In Minneapolis-St. Paul, the percentages were similar to those in L.A.: 68 and 76 percent, respectively.
But overall, local climate and social factors led to more lawn care variability than initially expected, both between and within cities.
"One of the take-home lessons is that responding to lawn care-related environmental challenges may require locally-tailored solutions in more cases than we initially thought,” Polsky says. “Place matters, there is not a one-size-fits-all approach."
Groffman adds that the management of urban and suburban areas has a direct impact on water resources, carbon storage, and the fate of pollutants, like nitrogen and phosphorus. “Yards are where our environmental knowledge, values, and behavior are likely generated,” he says. “The good news is that individual actions, on a yard-to-yard-basis, can make a difference."
The project was supported by the National Science Foundation. It’s part of a larger initiative that is investigating how urban homogenization can be used to understand carbon and nitrogen dynamics, with continental-scale implications.
"Research on residential landscapes is critical to sustainability science,” says Henry Gholz, program director in NSF's Division of Environmental Biology. “The approach in this study can be used to test other ideas about how people who live in cities decide to manage their yards. This should open a new phase in the field of urban ecology."
--From press releases by the Cary Institute of Ecosystem Studies and the National Science Foundation. Lawn sprinkler photo by Dennis Tsang.