Do you want to slow climate change? Plant evergreens.
Plants, especially trees, play an enormously important role in the regulating climate change by capturing the carbon released by the burning of fossil fuels. Some have described them as the earth's lungs.
But not much is known about the role they play in the urban and suburban landscape, the one that most of us know and that is growing at a rapid rate around the world. It's one of the questions that must be answered for cities to figure out how to reduce carbon emissions and to set up carbon exchange systems.
Now, researchers at the University of Minnesota and University of California Santa Barbara, have gone to great heights to try to answer that.
They found that suburban plantings do play a role -- depending on the season.
View in summer and winter of a suburban St. Paul landscape from the 500 ft tall KUOM tower where measurements for the study were made.
“We know cities and suburbs are net emitters of CO2 due to fossil fuel emissions, and vegetation cannot offset this completely," said Emily Peters, a postdoctoral fellow with the university’s Institute on the Environment "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.”
She and her co-researchers put sensors way up high on a tower above a St. Paul suburban neighborhood. It measured tiny changes in CO2, temperature, water vapor and wind. They found that for nine months of the year, the suburban landscape added CO2 to the atmosphere from cars, engines and other sources. But during the summer, however, suburban greenery absorbed enough CO2 to balance out fossil fuel emissions within the neighborhood. Peak daily uptake was close to the low end of what hardwood forest would absorb.
Different kinds of plants were better at it than others. For lawns, peak carbon uptake was in the spring and fall because they were stressed by summer heat. But 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, they found.
The study was published this week in the Journal of Geophysical Research – Biogeosciences.