Indiana’s forests help balance carbon

Reprinted here with the permission of the Bloomington Herald-Times

Two IU researchers attempt to make results understandable, usable for public, lawmakers

By Dawn Hewitt
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11/18/2011

Would it bother you if your car excreted a charcoal briquette each time you drove a mile?

It does, but that amount of carbon goes into the atmosphere and not onto the roadway.

Two Indiana University geography department researchers are studying the carbon cycle, the balance — or imbalance — between carbon emissions from natural and manmade sources and absorption and storage by forests, and they think the public and lawmakers ought to know what they are learning.

Professors Faiz Rahman and Danilo Dragoni use federal grants — taxpayer money — to fund their research, and they have presented their findings at local public libraries, adapting their results to show political boundaries.

They aren’t advocating policies, but they are attempting to make their findings more understandable and useful to voters and lawmakers.

Atmospheric carbon

Their work is based on several well-known facts:

• Growing vegetation takes carbon dioxide out of the atmosphere. Natural decomposition, cutting down forests and burning fossil fuels put carbon into the atmosphere.
• As atmospheric carbon increases, the surface temperature of the Earth increases.
• Both have been increasing for the past century.

“There’s no denying that the global temperature is going up,” Rahman said at a talk Tuesday evening at the Monroe County Public Library.

Need to know

We need to understand the carbon cycle, Rahman said, because the amount of carbon in the atmosphere is increasing at a rate unprecedented in history, as documented in core samples of Antarctic ice.

A warming planet will change ecosystems and individual species, he said, since “all of us, all living things, need a specific temperature range.”

The temperature is not changing at the same rate at all locations across the planet; some places are warming more than others.

Similarly, some places emit more carbon than they take in, while other places absorb more atmospheric carbon than they emit, and that’s the crux of Rahman and Dragoni’s research.

The scientists study carbon absorption by forests, which globally absorb about 4 billion tons of carbon per year. Most of that takes place in tropical forests, which are being cut down at an alarming rate.

Earth’s temperate forests capture about a billion tons of carbon per year, and the eastern deciduous forests, such as those in Indiana, are the most effective carbon-absorbers in North America.

The researchers are looking at carbon absorption at many levels: in the soil of the forest floor at Morgan-Monroe State Forest, in individual trees at ground level and the forest understory there, using a cherry picker to study the tree tops, from a tower rising high above the state forest, from data collected in an airplane and from NASA satellite data for the biggest picture.

Data from different levels of resolution show that the forest and the wider landscape aren’t homogenous in their ability to absorb carbon.

Their data collection includes many different indicators of carbon absorption and emission, and the tower is one of hundreds of carbon-sampling “Fluxnet” towers across the planet. It has been collecting carbon data for 13 years.

Seasons change

During that period, Fluxnet towers across the eastern United States showed that the summer growing season was extended and vegetative senescence — autumn dormancy — has been pushed back by about 20 days. The growing season in eastern North America is longer than it was a few decades ago.

In the South, the growing season has shifted and is now starting later and extending later into the autumn months.

“If these trends are confirmed, the length of the season in the North is catching up with length of the season of the South,” Dragoni said. “That’s a pretty dramatic effect.” Dragoni said that the data he has collected show that Morgan-Monroe State Forest increased its carbon uptake between 1998 and 2008 by almost 30 percent.

Data from 2009 and 2010 were exceptions. In 2009, carbon absorption in Morgan-Monroe State Forest was the lowest since data collection began. That summer was rainier and cloudier than normal. The summer of 2010 was extremely dry. “Our measurements had never seen such a drought,” said Dragoni, who added that the forest’s growth and carbon capture was clearly affected both years.

Work ahead

As the global climate continues to warm, the weather is expected to have more extremes: more severe storms, more droughts. What will be the effect on the forests that take carbon out of the atmosphere?

Rahman and Dragoni said that the answer to that question can’t be discovered in a laboratory. “Every year is an individual experiment,” Rahman said. “If we had stopped in 2008, we wouldn’t have known what happened in 2009 or 2010,” he said. “We learned something from those years as well.”

Since taxpayers ultimately fund their research, they are taking their results on a road trip to venues across Indiana to share their findings with the public. They made their data into maps understandable by nonscientists and potentially useful for lawmakers: carbon absorption and emission by political district, for both the Indiana House and Senate.

The maps indicate where carbon emissions are highest: near coal-fired power plants and steel mills; and where carbon absorption is greatest: near forests. Of course, atmospheric carbon doesn’t observe political boundaries.

“As scientists, we don’t make policies,” Rahman said. “But maybe scientists should have a chair at the table. Maybe scientists should be part of the discussion. We want to give this information to policy makers in a way they can understand.”

Rahman said they want lawmakers to realize that forests have value beyond timber and watershed protection: They help regulate the global temperature. Both researchers said there’s a lot they still don’t know about the relationship between forests and the climate. But they expect the forest ecosystems of Indiana to change in the next few decades.

“We live in a transitional forest zone,” Rahman said. “We’re not New England, and we’re not Tennessee.” Some tree species in Indiana, such as sugar maple, might suffer as temperatures rise, and warmth-loving trees might become dominant.