Carbon Dioxide Findings Raise Biodiversity Concern

This is one of the questions that comes to mind when Hormoz BassiriRad, assistant professor of biology at the University of Illinois at Chicago, contemplates practical applications for his research on how plants and ecosystems respond to environmental stresses, such as elevated levels of greenhouse gases.

BassiriRad has some doubts about Illinois' ComEd and other utility companies' hopes for "offset credits," whereby industries can save some of their pollutant allowances in the congressionally mandated emissions trading market by planting trees to remove carbon dioxide from the air. If nothing else, his research shows it's not easy precisely to quantify and verify the amount of carbon sequestered by forest trees.

"Each time we carry out another round of experiments, we solve an additional part of the puzzle," said BassiriRad. "Right now people are really interested in the question of 'sinks,' or systems that take carbon dioxide out of the atmosphere. Naturally, terrestrial ecosystems are a huge sink for atmospheric carbon dioxide. However, it remains to be seen if this capacity will increase, decrease, or remain the same in the future climate. The research we do is part of a nationwide effort to tackle this question."

Among the major ecosystems of the world, temperate forests of conifers and broad-leafed plants such as maples, oaks and birches form the largest terrestrial sink for carbon, and recent studies indicate that temperate forests of North America are a larger carbon sink than previously thought. They may even contain the so-called missing carbon -- accounting for the fact that carbon dioxide levels in the northern hemisphere are lower than models predict.

"The problem is to quantify the effect, species by species," said BassiriRad. "Even if the system's capacity for carbon sequestration increases with higher atmospheric carbon dioxide levels, there are unanswered questions about species diversity. Different species appear to have different responses to elevated levels of carbon dioxide."

"We're still very cautious about concluding anything from our experiments," he said. "But if it is true that different species respond differently, this has tremendous implications for biodiversity. Some species within a community might have a competitive advantage as greenhouse gases rise, and some might die off."