A Sound in the Forest: Trees and Climate Change

Doug Heiken (pictured, left) from the NGO Oregon Wild appeared at the Public Interest Environmental Law Conference last weekend as part of a panel on forests and climate change. His talk took the form of contrasting myths and realities about forests. These are some of the issues that his presentation touched on.

Forest Fires
Claim: It is sometimes said that forests are not good places to store carbon because forest fires can release stored carbon through combustion. e.g. "when a tree burns it releases all the carbon it previously stored"
In Reality: Logging a given area of land emits far more carbon than if a forest fire ran through the same area (more than twice as much, in fact) because not all trees are destroyed by forest fires. Large dead trees can last for many decades. Also, forest fires create charcoal - a stable form of carbon that often gets incorporated into the soil. As Mark Harmon, of Oregon State University, said, "If it were the case that when there was a forest fire all of the trees burned up completely, why would there be fights about timber salvage?"

China
Claim: China's forests are rapidly shrinking as they are quickly cut down as a consequence of the country's fast economic growth.
Reality: China is one of the areas of the world where forestcover is growing most quickly. That said, the main explanations for this growth are a low baseline and that much of the growth is composed of monoculture plantation forests grown on very short rotations.

Old Forests Good
Claim: Large swathes of forest are frequently protected with the sole benefit that a very small number of animals are protected. For example:

"One Million two hundred thousand acres of land closed to development for the sake of 18 Pygmy Owls. Yes, the U.S. Fish and Wildlife Service supported by a few radical green environmental groups proposes this huge acreage to be set aside for 18 Pygmy Owls." (Source: The Most Expensive Animal Alive? by the Pima County Coalition For Multiple Use)

Reality: One of the significant benefits of forests that such analyses ignore is the way that mature forests act as carbon sinks. Mature forests capture more carbon during their lifespans than forests that are grown and cut on shorter rotations because of multiple factors, including:

1. Below Ground Sequestration: Forests store massive amounts of carbon in the soil in the form of live and dead roots, woody debris, charcoal, and the vast below-ground ecosystem supported by photosynthate received from trees. Logging cuts off the food supply for the below-ground ecosystem which rapidly dies and decomposes, thereby emitting a significant amont of carbon into the atmosphere after trees are cut. So, it is not the case that the carbon is just embodied in the wood that is then used for things like building houses. (Oregon Wild Report)
2. Temperature and Decomposition: Forests that have been thinned (say, by selective logging) are warmer than they otherwise would be. This is because the decline in forest canopy exposes the soil to more sunlight which raises soil temperature and thereby accelerates the rate of decomposition, which in turn emits more carbon than the forest otherwise would have.

In sum, the presenters at this panel - some of whom had individually spent decades in academia studying forests - were highly skeptical of claims that human beings could manage forests (by cutting them periodically) in a way that would increase the net amount of carbon that the forests absorb when compared to a laissez faire approach that lets old growth forests get even older.

More detail about this and other aspects of the relationship between forests and climate change can be viewed in these slides from Oregon Wild's presentation:

Forest, Carbon, Climate Myths

View more presentations from Doug Heiken. (tags: products wood)