Analysis Shows American Forests Contain Enormous Carbon Reserves, But Available Measuring Tools Reflect Gaps in Underlying Data

Apr 9, 2008

WASHINGTON — A report released today by The Wilderness Society emphasizes the enormous carbon reserves held by forests in the contiguous states — roughly equivalent to more than 20 years of current United States greenhouse gas emissions from industrial and other sources. Across the U.S., public and protected forests generally store the most carbon. The analysis also cautions that existing carbon measurement tools have significant limitations due to gaps in the underlying data: old growth forests, in particular, may be undervalued.

"This analysis shows that public forest land, and especially reserved lands, typically store more carbon per acre than private forests," noted Ann Ingerson, an Economic Research Associate at The Wilderness Society and co-author of the new study. "While it is evident that protecting and restoring forests promotes carbon storage, some common carbon measurement tools use data designed primarily to track timber supplies and may not fully reflect important stores like dead and down wood and soil carbon."

While the existing forest carbon modeling tools can be improved, several broad trends important for future public policy development already are apparent:

  • On average, public forest lands such as National Forests and State Forests appear to hold more carbon per acre than private lands. Also, reserved forest lands, where timber harvest is prohibited such as in Wilderness, National Parks, and National Monuments, typically hold more carbon per acre than non-reserved lands.
  • Existing measurement tools are based on models of intensively managed forests and may underestimate carbon stores on older or unmanaged forests; while also not accounting for old growth forests often being more resilient in the face of climate change.
  • Distribution of carbon varies across the landscape, but, in general, the amount of carbon stored above ground in trees - what we can measure with the most confidence — is less than half the total.

"Mature and old growth forests can store or sequester extraordinary amounts of carbon, such as in the forests of the Pacific Northwest," said Dr. Jerry F. Franklin, a Professor with the University of Washington's College of Forest Resources. "An analogy would be that older forests can be viewed as having very large capital reserves, whereas younger forests have high cash flow, or carbon uptake, but contain very little capital, such as sequestered carbon. There's also a high 'transaction cost' when you 'liquidate' this stored carbon by harvesting the forest. The harvested sites are significant carbon sources leaking carbon dioxide to the atmosphere for many years to decades following the harvest."

Policy makers at every level recognize the importance of forests in the global carbon cycle, and there is a growing consensus that protecting forestland and enhancing its carbon stores will be a component of climate change mitigation policy. As regional and national climate initiatives unfold, we need accurate measures of the carbon stored in forests and the changes in those stores over time.

"This report highlights three important policy issues," said Bob Perschel, the Northeast Region Director of the Forest Guild. "One, we need to keep forests in forests and not allow them to be converted to other uses. Two, reserve forests and wildlands are doing an excellent job of storing carbon and should remain intact. Three, we need to manage our working forests in ways that increase carbon storage and sequestration."

The Wilderness Society report, Measuring Forest Carbon: Strengths and Weaknesses of Available Tools, is authored by Ann Ingerson, M.S. and Dr. Wendy Loya, Ph.D. The report examines the four widely available carbon measurement tools; identifies five important trends concerning carbon stored on American forests; and makes several recommendations for improving the accuracy of future carbon reserve measurements.

Note: Additional Background on Carbon Cycling: A primer on the carbon cycle, especially the role of forests, and how forests will respond to climate change (along with several landscape graphics) provides useful background on the role forests will play in climate change.