The emerald expanse of a lawn is a symbol of eternal summer鈥攎aybe even more than we think. New research in the finds that lawns have a hefty carbon footprint and could be contributing to the greenhouse effect. They鈥檙e 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鈥檚 about as much carbon as it takes to fly halfway around the world. 鈥淲e found that the urban turfgrass system actually contributes to global warming. It鈥檚 a lot. It鈥檚 about two-thirds of the carbon emissions from agricultural fields [of the same area],鈥 Chuanhui Gu, a biogeochemist from Appalachian State University and author on the study, .
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鈥檛 all that surprising, considering that a lawn mower can produce as many emissions driving at 45 miles per hour. Moreover, used in urban areas in the United States goes to lawns. And then there鈥檚 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 .
For bird advocates, the word on lawns is hardly news. From a bird鈥檚 perspective, lawns have always represented an environmental threat鈥攁 kind of lush-looking wasteland. The formulaic patches replace natural habitat with what is essentially a monocrop. Turfgrass doesn鈥檛 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. 鈥淣ative trees and plants are proven to be significant carbon sink,鈥 Gu says. Meanwhile, to curtail greenhouse gas emissions, the study鈥檚 authors offer a lawn-care manifesto: Halve the amount of mowing, use water sparingly, and apply fertilizer only when the grass is first sown.
鈥淥ur study shows that by switching from intensive to a minimum lawn management scheme, we can cut down lawn greenhouse gas emissions by 70 percent,鈥 Gu said. 鈥淟awns can continue to be an environmentally friendly landscape in urban environments.鈥
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.