Trees benefit from excess carbon dioxide

Studies show carbon dioxide causes more than climate change.

by Anissa Stocks

Long considered a major driver of global climate change, a pair of studies by University of Minnesota researchers have revealed positive aspects of excess carbon dioxide in the atmosphere. A study by researchers at the University of Minnesota-Morris and the University of Wisconsin found aspen trees, a Minnesota paper industry staple, are responding well to excess carbon dioxide. The study, published Friday in Global Change Biology found that an increase in carbon dioxide has caused a 53-percent increase in the treesâÄô growth rate over the past 50 years. University of Minnesota professor Peter Reich published a related study in Science magazine showing that an increase in carbon dioxide may limit the damaging effects nitrogen pollution has on plant diversity. Chris Cole, a professor at Morris who co-authored the study on aspen trees, said the results are especially important in Minnesota and Wisconsin, where aspen span more than 7 million acres oftimberland. âÄúAspen are commercially, ecologically and emotionally important trees,âÄù he said. About 920 trees were studied throughout three regions of Wisconsin over a period of more than five years, but Cole said the results do not necessarily mean that aspen will continue to grow. âÄúTheyâÄôre growing in large part because of the effects of carbon dioxide,âÄù he said. âÄúThat doesnâÄôt mean growth rates will last down the line.âÄù Rick Lindroth, a professor at the University of Wisconsin and co-author of the aspen tree study, said researchers were surprised with the results. Oak and pine trees have not observed faster growth rates, making the study unique to previous research. âÄúWhat this means is our beloved forests are recognizing change,âÄù he said. âÄúThere was a âÄòwhat ifâÄô question that frequented the study âĦ Its results concluded that aspen responded well to carbon dioxide, which is fascinating.âÄù Lindroth said global climate change affects more than just temperature. Climate change, he said, played a large role in the studyâÄôs results. WisconsinâÄôs climate has stayed relatively consistent compared to other parts of the United States, Cole said. The study is the first to determine that growth rates in the region are directly linked to rising levels of atmospheric carbon dioxide. Lindroth called carbon dioxide a âÄúsuperfoodâÄù for the trees and said it is the driving force for aspen growth. Aspen trees were chosen for the study because of their ubiquity and because the trees are particularly responsive to changes in environment. âÄúAspen are unique âĦ The trees are sort of the white rat of the forestry world,âÄù he said.