Gannett News Service
(Coloradoan.com) - A new Colorado State University study of when and how trees absorb carbon could have far-reaching effects on years of previous and current climate change research.
The culmination of seven years of research has revealed that trees trap in their leaves less carbon dioxide than once thought. This means that there is an estimated 2 billion more metric tons of the greenhouse gas in the air that scientists say has, with others, contributed to a rise in the Earth's temperature.
"We're not taking the CO2 out of the air as fast as we thought we were," said Bill Bauerle, a CSU ecophysiologist and lead author on a study published Monday in the "Proceedings of the National Academy of Sciences."
"It's not that trees can't help (reduce the amount of carbon dioxide in the air); it's just that they can't as much," he said.
Bauerle and a team of researchers from CSU, Duke University and Tennessee's Oak Ridge National Laboratory have, since 2005, tested more than 23 species of trees in South Carolina and Colorado to see how much and how often in each type of tree photosynthesis occurred.
During photosynthesis, a plant takes in and converts sunlight into stored energy. An enzyme holds onto carbon dioxide after it diffuses into the leaves.
Daylight decreases incrementally following the summer solstice, which this year takes place on June 20. At the same time, trees' leaves begin to shut down and take in less sunlight - which means they take in less carbon dioxide.
At one point, measurements suggested that the world's vegetation absorbed each year about 58.7 petagrams of carbon, or 58.7 billion metric tons. The average U.S. household produces about 4 tons of carbon dioxide each year, and in 2010 Americas produced 6,821.8 million metric tons of greenhouse gases, according to the 2012 U.S. Greenhouse Gas Inventory Report on the Environmental Protection Agency's website.
The new study shows that the amount of carbon plants store is actually closer to 56.7 billion metric tons.
And while that's a difference of only about 3.4 percent, it's enough to "refine global models of atmospheric carbon cycling and predictions about the impact of climate change," a press release from CSU spokeswoman Jennifer Dimas said.
Scientists using the results of this study will be able to refine their assessment of how much carbon dioxide is in the Earth's air, Bauerle said, which will make it easier for people to figure out how to reduce resulting measurements.
Scientists previously assumed that as the climate warms, growing seasons would lengthen, more plants would grow and forests would absorb more carbon dioxide, Ram Oren, a professor at Duke University's Nicholas School of the Environment, said in the release.
But this doesn't mean that people should stop putting seeds in the ground as a means to improve air quality.
"Planting trees (is) still a good thing," Bauerle said. "We just misunderstood them a little bit."