|Wednesday What’s New: Urban Parks Not so Green?|
|Written by Heleigh Bostwick Wednesday, 27 January 2010|
Amy Townsend-Small, Earth system science postdoctoral researcher and lead author of the study, which is soon to be published in the journal Geophysical Research Letters, and a colleague, Claudia Czimczik, analyzed grass in four parks near Irvine, Calif. Each park contained two types of turf: ornamental lawns (picnic areas) that are largely undisturbed, and athletic fields (soccer and baseball) that are trampled and replanted and aerated frequently.
The two researchers evaluated soil samples over a period of time to ascertain carbon storage, and then determined nitrous oxide emissions by sampling air above the turf. Next they calculated carbon dioxide emissions resulting from fuel consumption, irrigation and fertilizer production using information about lawn upkeep and maintenance from park officials and contractors. Results of the study showed that nitrous oxide emissions from lawns were comparable to those found in agricultural farms, which are among the largest emitters of nitrous oxide globally.
In ornamental lawns, nitrous oxide emissions from fertilization offset just 10 percent to 30 percent of carbon sequestration. But fossil fuel consumption for management, the researchers calculated, released about four times more carbon dioxide than the plots could take up. Athletic fields fared even worse, because -- due to soil disruption by tilling and resodding -- they didn't trap nearly as much carbon as ornamental grass but required the same emissions-producing care. "It's impossible for these lawns to be net greenhouse gas sinks because too much fuel is used to maintain them," Townsend-Small concluded.
Excerpted from Science Daily: Urban 'Green' Spaces May Contribute to Global Warming