The perfect green lawns of suburbia are traditionally seen as good for the Earth, as the green spaces counteract emissions that cause global warming. But that's not necessarily true, according to a new study from the University of California, Irvine. ScienceDaily reports that, at least in Southern California, the fuel consumption required to maintain these perfect lawns outweighs the benefits of having them. In fact, green lawns actually do more harm than good.

It's hard to imagine that the waves of grass dotting our cities and suburban areas are anything but eco-friendly. After all, grass absorbs carbon dioxide from the air and stores it as organic carbon in the soil, making them important carbon sinks. However, this new study shows that greenhouse gas emissions from fertilizer production, mowing, leaf blowing and other lawn management practices are four times greater than the amount of carbon stored by ornamental grass in parks.

Amy Townsend-Small is a researcher and lead author of the study which will be published in the journal Geophysical Research Letters. As she told ScienceDaily, the carbon-storing benefits of lawns are counteracted by fuel consumption. What’s more, she says "the current trend is to count the carbon sinks and forget about the greenhouse gas emissions, but it clearly isn't enough." Further, turf grass covers an estimated 1.9 percent of land in the continental United States. This makes it the most common irrigated crop.

Townsend-Small and colleague Claudia Czimczik came to their conclusions after analyzing grass in four parks near Irvine, Calif. They looked at two types of turf: ornamental lawns in picnic areas and those of athletic fields that are repeatedly disturbed. Then, using lawn upkeep information from park officials, they calculated carbon dioxide emissions resulting from fuel consumption, irrigation and fertilizer production. 

In the ornamental lawns, nitrous oxide emissions from fertilization offset just 10 percent to 30 percent of carbon sequestration. In the athletic fields, where upkeep was much more rigorous, it was even worse. Consequently, Townsend-Small concluded "it's impossible for these lawns to be net greenhouse gas sinks because too much fuel is used to maintain them."

For further reading: Urban Green Spaces May Contribute to Global Warming