The critical time to preserve rainforest is now before more valuable forest disappears forever.

It is wise to recognize that avoided deforestation is valuable even without a guarantee of permanence. Carbon sequestration doesn’t have to be permanent to be part of a climate change mitigation program.

There are two ways that temporary commitments to carbon sequestration buy time to act on climate change:

1) Temporary sequestration buys insurance against catastrophe in the face of uncertainty. The climate system is unstable. Small changes can trigger large and irreversible impacts, such as those that apparently shifted the Sahara from being heavily vegetated to desert (Foley and others 2003; Schneider 2004).

There is a fear that too much CO2 in the atmosphere, or too rapid a rise in CO 2, could have the same kind of catastrophic effect. But we don’t know the thresholds beyond which such a catastrophe could occur. In the face of such ignorance, it is prudent to buy insurance—that is, to try to keep CO2 levels low and rising slowly. Gitz, Hourcade, and Ciais (2006) show that forest carbon could be a crucial, cost-effective part of a long-term climate change mitigation program.

In their model, inexpensive forest carbon offers insurance over the next few decades—after which the world may be better able to assess the risk of catastrophe. If a dangerous threshold is then imminent, the world could continue to rely on forests as a carbon sink, or step up investments in geological carbon sequestration. Temporary sequestration could be a bridge to a clean energy future. Under Kyoto rules, industrial countries need to meet limits on total carbon emissions. They can park their carbon in trees temporarily, but when their storage contracts are up, they need to put that carbon someplace else—or reduce emissions someplace else.

This strategy will work nicely if, at the end of the contract term, there are new, cheaper opportunities for storing carbon or reducing emissions.Translated from the project to global scale, this suggests that a temporary, renewable decision to protect forests could buy time for technological advance. The strategy would be to protect threatened forests with low opportunity costs. Over time those costs might rise if there is pressure for agricultural expansion.

Development of emissions-reducing technologies would then allow the option of substituting emission reductions for continued forest maintenance. (But, as the next section suggests, forestholders at that time might choose not to exercise that option.)

For the global community it makes sense to approach climate change mitigation through a program that uses not-necessarily-permanent avoidance of deforestation as one way to buy time for more effective investments in energy research and development. There is no need to tie the two approaches at a project level, but rather to move toward simultaneous global implementation of avoided deforestation and more vigorous research and development.

The faster that cheap emissions-reducing technologies are developed, the less time has to be bought through temporary sequestration—potentially allowing forest owners to exercise their option of forest conversion.

2) Temporary sequestration could become permanent. However, the history of the forest transition suggests that “temporary” sequestration could bridge the trough of the transition and end up being permanent.

Many places face temporary pressures to convert forests for small gains. A 20- to 40-year effort to halt deforestation would not involve large opportunity costs, so equitable compensation could be arranged. At the end of that period, rising wages and appreciation of biodiversity values could prompt a reevaluation of the desirability of forest conversion. The forest owner and the host country may not want to exercise their option for conversion at that time. Thus temporary efforts to avoid deforestation provide a valuable climatic service and may end up being permanent.