If there's only a few things you should know about carbon dioxide, know that it is a naturally occurring chemical compound, one that has been produced at very high rates due to the burning of fuels like coal and gasoline, and that high concentrations of it are exacerbating climate change. So it's great that plants use carbon dioxide in the process of photosynthesis, absorbing CO2 and emitting oxygen. This, it's becoming increasingly clear, is one of many reasons trees are literally valuable assets in CO2-emitting urban areas.
But trees aren't our only aides from the plant kingdom. According to new research from UC Santa Barbara and the University of Minnesota, carbon dioxide is also sucked up by other kinds of urban greenery, including the alternately maligned and American-Dreamed front lawn. That green symbol of suburban excess may actually be helping out the planet.
Monitoring CO2 levels in the suburbs just outside of St. Paul, Minnesota, the researchers found that the carbon uptake of urban greenery – including trees and lawns – was significant enough to balance out the carbon emissions from fossil fuel burning at a neighborhood level, at least during the summer months. This research is published in the July 4 issue of the Journal of Geophysical Research – Biogeosciences.
"Lawns' peak carbon uptake occurred in the spring and fall, because they are made up of cool-season grass species that are stressed by summer heat," said lead author Emily Peters, "while trees had higher CO2 uptake throughout the summer." Evergreen trees maintained their CO2 uptake for a longer period of time than deciduous trees because they keep their leaves year-round; deciduous trees lose their leaves in fall and winter.
But before we start sprinkling Bermuda grass seeds all over the country, the researchers note that the urban greenery was not actually able to suck up enough carbon dioxide over the course of the year to offset emissions from fuel burning. They also note that a place like suburban St. Paul gets enough rainfall to eliminate the need for irrigation. Planting grass in places with less rain may reduce some carbon dioxide, but it'll also lead to a huge drain on water resources. And there's only so much carbon dioxide that plants can take. We can plant all the grass and trees we want, but if we don't cut down our own carbon dioxide emissions, a front lawn covering the entire continent won't be able to suck it all up.
Photo credit: Flickr/LancerE