The New York Times’ Dot Earth blog reports on a new study on urban green space from Geophysical Research Letters, a publication of the American Geophysical Union, which contends many urban green spaces emit more greenhouse gases (GHGs) than they absorb. This is due to the high amounts of emissions from lawn irrigation, fertilizer, mowing, and leaf blowing. The study argues: “Turfgrass lawns remove carbon dioxide from the atmosphere through photosynthesis and store it as organic carbon in soil, making them important ‘carbon sinks.’ However, 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.”
Claudia Czimczik, a researcher at University of California, Irvine, and a co-author of the study, told Dot Earth: “Lawns weren’t initially invented to store greenhouse gases — they have a lot of other purposes such as recreation. But there is a lot of recent political discussions about lawns as carbon sinks, and if that is the case we need to consider the whole package.”
According to Dot Earth, the researchers looked at four parks in Irvine, including open lawns and athletic fields. Open lawns which use fertilizers emit “heat-trapping nitrous oxide,” which “offsets 10 to 30 percent of the carbon dioxide captured and stored.” Additionally, the fuel used in mowing and leaf-blowing ”releases four times more carbon dioxide than the lawns soak up. Athletic fields fare even worse because they require more maintenance.”
Czimczik said Californian parks may be a special case because park officials maintain their parks year round. More research needs to be conducted on the emissions of green spaces in other regions. She added that push mowers should also be considered.
Dot Earth points to the EPA’s GreenScapes program, which can encourages homeowners to think about land, water, air, and energy use in their lawn maintenance. Unfortunately, the article leaves out the Sustainable Sites Initiative (SITES), a comprehensive new rating system, which addresses all of these issues (see earlier post).
Also, read another recent article in The New York Times on the 2,200-acre FreshKills Park, which will feature native grasses, man-made meadows and wetlands, and, hopefully, will prove to be a carbon sink. In restoring the local ecosystem, FreshKills Park is successfully bringing back birds.