Is Your Yard Super Gassy?

Urban lawns aren’t quite as green as they seem.

The emerald expanse of a lawn is a symbol of eternal summer—maybe even more than we think. New research in the Journal of Environmental Management finds that lawns have a hefty carbon footprint and could be contributing to the greenhouse effect. They’re also not popular with birds, so it might be time to rethink this garden standard altogether.

Scientists calculated that a hectare of lawn (there are 259 hectares in a square mile) indirectly produces between 697 and 2,443 kilograms of emissions every year. On the higher end, that’s about as much carbon as it takes to fly halfway around the world. “We found that the urban turfgrass system actually contributes to global warming. It’s a lot. It’s about two-thirds of the carbon emissions from agricultural fields [of the same area],” Chuanhui Gu, a biogeochemist from Appalachian State University and author on the study, told The Independent.

But how does something as innocuous as grass carry so much weight in carbon? The true culprits here are the watering systems, gas-guzzling mowers, and fertilizers that go into shaping a lawn. The researchers tallied up the amount of energy used to keep up a lawn, and found that it heavily outweighs the amount of carbon dioxide captured by grass.

This isn’t all that surprising, considering that a lawn mower can produce as many emissions as a car driving at 45 miles per hour. Moreover, 60 percent of the water used in urban areas in the United States goes to lawns. And then there’s fertilizer, which produces nitrous oxide, a greenhouse gas that has 300 times more warming potential than carbon dioxide and stays in the atmosphere for up to 120 years.

For bird advocates, the word on lawns is hardly news. From a bird’s perspective, lawns have always represented an environmental threat—a kind of lush-looking wasteland. The formulaic patches replace natural habitat with what is essentially a monocrop. Turfgrass doesn’t contain the rich variety of grubs, seeds, or fruit needed to support avian life; neat and open lawns cut trees and shrubs out of the picture, robbing birds of nesting habitat and other foods.

There is a way out of this grassy gridlock, however. Replacing grass with naturally occurring trees and shrubs will coax birds back into the yard. “Native trees and plants are proven to be significant carbon sink,” Gu says. Meanwhile, to curtail greenhouse gas emissions, the study’s authors offer a lawn-care manifesto: Halve the amount of mowing, use water sparingly, and apply fertilizer only when the grass is first sown. 

“Our study shows that by switching from intensive to a minimum lawn management scheme, we can cut down lawn greenhouse gas emissions by 70 percent,” Gu said. “Lawns can continue to be an environmentally friendly landscape in urban environments.”

Gardeners can lead the flock on bird conservation and climate change, too, all by spending less time, energy, and money on their lawns. That sounds like a win-win situation.