I can’t let this go by without comment. Today’s New York Times has a big front page story on the prospects for mitigating climate change through forest growth and protection. It has stories about successes in Costa Rica and Brazil, with feel-good mentions of the butterflies, monkeys and other creatures whose habitats can be saved. Only the most churlish reader would fail to jump on the bandwagon.
Churlish like me. Actually, I’m completely on the bandwagon for protecting forest biodiversity, ecosystem services, habitat for the millions of human forest-dwellers, especially from traditional cultures, and the recreation and scientific values that natural forests can provide. And I think there are modest gains to be made in climate protection, mainly having to do with the timing of atmospheric carbon loading. But the story is profoundly misleading on its most important claim, that a ton of carbon withdrawals due to planting trees or not cutting down trees that were expected to be cut exactly offsets a ton of carbon released by extracting and burning fossil fuels. Its casual use of “emissions” numbers assumes that this equivalence holds, and it’s wrong.
Specifically, the article claims that by massively increasing forest cover we can “pull a sizable fraction of human-released carbon dioxide out of the air and lock it into long-term storage.” This is carbon we can then allow ourselves to release through the use of fossil energy, knowing we can make it go away. It’s convenient to believe this, of course, since the resistance to cutting back on coal, gas and oil is intense, but what if it’s not true? If we struggle to reach any fossil fuel carbon target, what’s the cost of setting the target too low?
The issue of forest sequestration and atmospheric carbon is far too complex to delve into here. I can make only a few simple points.
1. The impact of forests on carbon cycling is complex and depends on a number of specifics, like the latitude of the forest, specific tree species and soil types. Any simple statement about the effect of “forests” on global climate change is misleading. It may well be the case that some forests (mainly boreal) are net contributors to climate forcing.
2. Carbon is withdrawn from the atmosphere when it is fixed in plant growth. It returns to the atmosphere when plants decompose, as they will. The net effect depends on the change in forest cover, not its amount. To alter climate forcing over a given time period, say a century, this change has to be permanent over that same time period. Now, why might a change in forest cover not be permanent? Two good reasons: future land use or resource decisions by people and the effects of climate change itself. If people 50 years from now cut down a forest we plant today, the effect is simply to reduce carbon loading in the present in order to speed it up in the future. But climate change makes the problem even worse. First, changes in temperature and precipitation patterns that are already baked in are likely to cause significant forest die-backs. A portion of the trees we plant today are essentially doomed, although we don’t know which ones or how many. Second, it is likely there will be severe impacts on agricultural productivity, especially toward the later years of this century, and that may lead to renewed forest-clearing to meet food needs. The bottom line is that a ton of carbon released by burning fossil fuels is a definite ton, but a ton sequestered through forestation is a maybe ton, depending on future events we can’t control or predict.
3. The Times article played up natural forests, like Cuatro Rios, a recovered rainforest in Costa Rica. Many of the projects financed by Reducing Emissions from Deforestation and Forest Degradation (REDD), a UN-based scheme for funneling carbon offsets into forestation, however, support monoculture plantations of fast-growing trees like eucalyptus, since this bulks up the short run sequestration numbers. Such forests are of dubious value as habitat, and people from traditional forest communities are at risk of being expelled from their homes to make way for industrial tree operations. Managing forests for carbon is not the same as managing them for cultural and ecological values.
So why, if a non-specialist like me can make these arguments, are the majority of climate scientists and environmental NGO’s so enthusiastic about the use for forestry for carbon mitigation? I think there are a number of answers, with different people moved by different considerations.
1. From a scientific point of view, the problem of time frames simply doesn't come up in climate models, since the models are intractable over the longer time horizons that are relevant for policy purposes. We know there is a short run sequestration benefit, and how much of that benefit will be reversed (as some of it almost certainly will be) in decades to come is not something the models can tell us. Of course, such models also don’t include future human actions that can undo forest gains, nor can they. The scientific credo is to say what you know and remain silent about what you don’t—minimization of Type I error. It’s great for the progress of knowledge but often disastrous for pubic policy.
2. For those who care about natural forests, as most environmental groups do, the linkage between forestry and climate is immensely convenient. National governments and international organizations have lined up behind REDD and similar programs, and it would seem to be insane not to encourage and benefit from this. If the green groups can ensure that the definition of what constitutes a “forest” excludes mono-plantations and land grabs that expropriate indigenous people, their goals may be realized. (It could happen, but I wouldn't bet on it.) But signing on to a myth about climate in order to advance a forest agenda has costs for the climate.
3. The global forestry programs target tropical forests in developing countries. They have the potential to transfer income from the rich to the poor—if the money isn't funneled into the pockets of politically-connected business interests that have seized forest lands and now demand to be paid in order not to clear them. This is another potential convenience. It’s so difficult to squeeze genuine development aid out of the wealthy countries, and if forest carbon can be a conduit, why not support it? But this too ends up sacrificing carbon goals because the political will doesn't permit a direct, honest solution.
Am I missing something? I wouldn't be surprised, and I’d be happy to be set straight. I would especially encourage readers conversant with the science aspects of forestry and carbon cycling to respond.