Well, I didn't really intend to go on and on about my anti-lawn crusade but this is rather interesting:
(Thanks to Dave Varner of the CNPSSD for sharing)
Grass for city parks may add to greenhouse-gas emissions
Creating urban parks might seem like an effective way to sequester more carbon. But maintaining the turfgrass for these green spaces can actually release more greenhouse gases than the grass absorbs, researchers say.
Based on a study of four parks in Irvine, California, the team determined that athletic fields did not sequester organic carbon, probably because they underwent frequent tilling and sod replacement. Fertilization also caused emissions of the powerful greenhouse gas nitrous oxide, estimated at 0.1 to 0.3 grams of nitrogen per square meter annually.
The study, in press at Geophysical Research Letters, notes that the parks’ lawns did store organic carbon. But this benefit was outweighed by carbon dioxide emissions from irrigation, fertilizer production, and fuel for tasks such as mowing and leaf-blowing. In short, these green expanses seem to be contributing to global warming – not counteracting it. – Roberta Kwok
Source: Townsend-Small, A., & Czimczik, C. (2010). Carbon sequestration and greenhouse gas emissions in urban turf Geophysical Research Letters DOI: 10.1029/2009GL041675