2. FORESTS: Study questions counts of carbon stored in trees (ClimateWire, 04/10/2008)

Christa Marshall, ClimateWire reporter

Four U.S. Forest Service tools that are used to estimate the amount of carbon stored in trees leave enough gaps in data that policymakers should hesitate from relying on their measurements as a means to reduce global warming, says a study released yesterday.

"Given incomplete information about forest carbon, climate change policies should focus on direct emissions reductions," wrote the study's co-author, Ann Ingerson, an economic research associate at the Wilderness Society, which released the report. Wendy Loya, a Wilderness Society ecologist, was the other author.

The four Forest Service tools examined -- including the Carbon Calculation Tool (CCT) and the Carbon OnLine Estimator (COLE) -- originally were designed to measure timber volumes, Ingerson said, noting they were appropriate for broad comparisons of forest carbon storage across large regions.

But the numbers the tools provide "may be too low" for measuring carbon in old-growth forests and too unreliable to measure year-by-year changes in forest-stored carbon, Ingerson said. The potential undervaluing of old-growth forests is problematic because younger trees sequester less of the greenhouse gas and may be more vulnerable to climate change.

The tools also lack precision for use in forest carbon offset projects, she added.

There are other methods for measuring carbon in trees at the "project" level, or at a level appropriate for the purpose of registering or selling carbon credits, said Neil Sampson, president of the forest and agriculture consulting organization The Sampson Group.

Such on-the-ground sampling methods were accurate to "plus or minus" 5 percent, he said, asserting that Ingerson's report did not provide anything new.

Ingerson conceded that point, but emphasized that she wanted to compile research information in one place to make existing information in journal articles and obscure documents accessible.

Can you trade it if you can't count it?

The climate change bill sponsored by Sens. Joseph Lieberman (I-Conn.) and John Warner (R-Va.), which is moving through the Senate, would set up a carbon cap-and-trade system and calls for forest-based offsets.

"If you own land, and plant a bunch of trees, you can get them certified as an offset project by the Agriculture Department and the Environmental Protection Agency," said a Senate Democratic aide familiar with the legislation, which is slated for a floor vote later this year.

However, several experts noted that the legislation leaves it to the federal agencies to specify the protocols for measuring tree carbon, and that field sampling likely would be used rather than the Forest Service tools examined by Ingerson.

Still, field sampling on broad swaths of land would be a "daunting task," Ingerson said, raising doubts about the reliability of national data on carbon stored in forests.

She also expressed some concern that the U.S. Department of Energy's Voluntary Reporting of Greenhouse Gases registry -- which uses data computed using one of the tools examined in the study -- could become mandatory as part of a carbon trading system.

And an early version of one of the tools she analyzed -- the General Technical Report NE-343 -- already is the basis for forest carbon trading on the Chicago Climate Exchange, said Richard Birdsey, a biological scientist at the Forest Service.

The Chicago Climate Exchange does have an "insurance" system to account for any inaccuracy, one analyst said, using the example of 100 tons of estimated carbon, which would actually be traded at around 60 tons.

Like Ingerson, Birdsey said the Forest Service has done the best possible job of assessing carbon with the available funds. He noted that the tools continue to improve and that they were useful for reporting on forest management activities that "may be used for offsetting carbon emissions" down the road.

Public forests store the most CO2

For now, he emphasized they were helpful for answering questions such as: "What is the carbon potential in the eastern United States for converting marginal crop land to forest?"

Regardless of how the tools ultimately are used, the report provided an idea of the amount of carbon at stake.

Forest reserves in the contiguous United States hold the equivalent of about 20 years of current U.S. greenhouse gas emissions. Twelve states, led by Oregon, California and Washington, hold over 50 percent of the approximately 153 billion metric tons of C02 stored, the study said.

More carbon also exists on public forest lands than on private lands, and a huge chunk of reserves may lie in the least-studied areas of forests, such as in below-ground biomass or in the soil, Ingerson noted.

For Ingerson, that means that forests need to be protected and to be kept out of the "carbon accounting" business until data can provide a more complete picture.

"We need 'do no harm' policies," said Ingerson. "The big takeaway from this study is that we need to have humility about what we don't know."

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