The United States is becoming a much greener place, as turfgrass pops up around the country as a staple of houses and parks everywhere. Its growing ubiquity, although widely considered to be a good thing, comes with a host of environmental considerations.
There are some 80 million home lawns across the country, according a study by Ohio State University. Half of those lawns are maintained by a mow-only practice, which means they do not get treated with fertilizers, irrigation or pesticides, the lowest level of care.
Among conservationists, lawn care matters because certain techniques can cancel out some of greenery's environmental benefits. Among other things, turfgrass helps captures carbon and other pollutants.
For lawns that receive low-level care, the average carbon sequestration rate is lower than those maintained by "lawn care service or apply fertilizer multiple times a year," the industry's idea of best management practices, the Ohio State study found.
A separate study by environmental and energy consultant Ranajit Sahu found that, "for the average, managed lawn," turfgrass captures "significant amounts of carbon" than what a "typical lawnmower" produces. Unlike Ohio State's study, which centered mainly on lawns without much external treatment, Sahu looked at lawns that included watering and fertilizer as part of their maintenance.
With lawns, little things can mean a lot
Sahu's study confirmed what other researchers have found: lawn maintenance habits have a significant impact on grass' ability to pull CO2 out of the atmosphere. Some of the smaller details—such as grass clippings and length—can have big influence on whether turfgrass helps or hurts the environment.
"Most people mow their lawns too short," says Tim Johnson, director of horticulture at Chicago Botanic Garden. This, he says, creates opportunities for weeds, which in turn creates opportunities for herbicide use, which can produce carbon and harm the environment.
Turfgrass that's allowed to get overly weedy, under-fertilized or irrigated improperly can make lawns patchy and more likely for soil erosion, said Susan Barton, associate professor in plant and soil sciences at the University of Delaware.
Home lawns, however, are just part of the picture. There are countless turfs in parks, golf courses, athletic fields and business parks across the country, most of which require considerable levels of maintenance. The turfgrass industry, estimated to be worth at least $40 billion, includes a broad array of sod farms, maintenance, equipment and manufacturing.
Demand for more greenery—including golf courses, which use "highly managed turfgrass," according to experts at the University of Florida—have some concerned about the effects of seemingly relentless turfgrass expansion.
The perils of green creep
A 2012 study by the University of Pennsylvania found that converting vacant lots into green ones, which consisted of grass and trees, reduced crime and made people feel safer.
J. Scott Ebdon, professor of turfgrass science at the University of Massachusetts, Amherst, said in an interview that as "urbanization increases in future years," so will the total acreage of lawn in the United States.
University of Delaware's Barton, however, worried that sort of growth could create "wasted land" and diminished natural areas. She suggested replacing turfgrass with a "forest or meadow" that can provide "much more diversity and many more ecosystem services," like clean water, clean air and wildlife support.
"We need to get ecosystem services from suburbia now," she says.
Morris of the National Turfgrass Federation acknowledged that there is some lawn overkill happening, but insisted it was key to environmental health as well as aesthetics.
"While turfgrass may be overutilized in some situations, it is a group of plants that can provide tremendous landscape function," he said.
Additionally, according to Ebdon "actively growing and healthy turf" can provide benefits like noise and heat reduction, topsoil preservation and "entertainment value." But a loss in turf density due to problems like diseased grass and insects, can lead to a "significant loss" to these functions and benefits.
Maintaining the "all-important function" of turfgrass systems—carbon reduction—is what Ebdon called "the single most important issue." This includes advancing grass variety and adopting lawn practices that cut down on mowing, water and pesticides, he says.