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Climate change scientists take to the trees

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Like climbing trees? Not afraid of heights? Climate change researchers might have a job for you some day.

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For the last four years, Christian Körner of the University of Basel, in Basel, Switzerland and his colleagues have been working in a laboratory that's 35 meters in the air. That's more than 100 feet high and taller than a 10-story building.

The lab is actually the top of a forest near Basel, and the researchers have been going up there to study how carbon dioxide affects tree growth.

During photosynthesis, plants soak up carbon dioxide, water and sunlight to produce energy. The carbon is ultimately used to build the growing tree's leaves and other parts.

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Therefore, some experts have proposed that forests might help reduce the effects that fossil fuel emissions -- from cars, factories, etc. -- are having on global climate. The idea is that the trees might grow faster with more carbon dioxide, removing at least some of this gas from the atmosphere.

In earlier studies, researchers tested this idea using large systems of hoses to release extra carbon dioxide in plantations with relatively young trees that were all the same species. (These trees were fairly short and easy to study.) The researchers found that in some cases, the carbon dioxide did seem to help the trees grow.

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Young plantations don't necessarily behave the way mature forests do, though, which is why Körner and his colleagues decided to start climbing.

They used a giant construction crane to hoist a gondola up to the treetops of a Swiss forest that had much taller, older trees of different species. There, they wove tubes, which sprayed out carbon dioxide, through the trees. Riding to the top of the forest in the gondola, the researchers were able to sample the air and measure the tree growth.

After four years of this research, the scientists concluded that the carbon dioxide didn't seem to be causing the trees to grow faster, although the specific effects were different for various tree species. They describe their findings in the 26 August issue of the journal Science.

Although researchers still have a lot to learn about the relationship between tree growth and carbon dioxide, this study suggests that this type of forest may not able to significantly counter the effects of fossil fuel emissions. Humans still need to find a way to reduce these emissions ourselves.