Bob CollinsHow do you like the suburbs now, city slickers? Our perfect lawns and could-be-anywhere gardens and landscaping are sucking a generous helping of carbon dioxide out of the air.
Today’s mailbag brings this news release from the University of Minnesota which says plants in the suburbs are offsetting fossil fuel emissions in the suburban paradise. Let’s see you do that, my city pals.
Emily Peters, a postdoctoral fellow with the university’s Institute on the Environment and Joe McFadden, an associate professor in the Department of Geography at UC Santa Barbara, published their findings in the current issue of the Journal of Geophysical Research – Biogeosciences.
“Our study is the first to clearly show how much vegetation can change the seasonal pattern of suburban CO2 exchange,” Peters said. “We know cities and suburbs are net emitters of CO2 due to fossil fuel emissions, and vegetation cannot offset this completely. However, our study shows that vegetation is an important player in suburban CO2 exchange, and can even cause the suburban landscape to be a CO2 sink in summer
Placing several sensors high above the ground in a St. Paul suburban neighborhood, Peters and McFadden set out to record tiny changes in CO2, temperature, water vapor and wind. The researchers found that for nine months of the year, the suburban landscape was a net source of CO2 to the atmosphere. During the summer, however, suburban greenery absorbed enough CO2 to balance out fossil fuel emissions within the neighborhood. Peak daily uptake was at the low end of that which would be typical of a hardwood forest in the region.
The CO2-trapping activity of the vegetation differed by type, the study found.
“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 Peters, “while trees had higher CO2 uptake throughout the summer.” Evergreen trees maintained their CO2 uptake longer than deciduous trees did because they keep their leaves year-round.
The study was funded by NASA and is a first step toward quantifying the role of vegetation in extensive developed areas such as suburbs, which are the parts of urban areas that are growing most rapidly in the country. Potential uses for this type of research include urban planning, where land use and vegetation choices are major decisions, and policy decisions based on reducing greenhouse gases.
In other news, I cut down a spruce tree last weekend. Whoops.
Timing is everything.
