The Albedo Effect and Forest Carbon Offset Design

Forestry and land-use change are often considered in the context of a greenhouse gas cap-and-trade program, in recognition of their influence on net carbon flux and their ability to mitigate climate change via increased carbon sequestration. The climatic impacts of forests are not limited to atmospheric greenhouse gas concentrations, however, and a growing body of research suggests that albedo-related climatic changes stemming from land-use change may diminish or counteract the climatic benefits of sequestration. Because forests are generally darker than bare or agricultural land they absorb relatively more solar radiation, which may exert a local worming influence. This phenomenon is known as the "albedo effect." Thus, a "carbon-only" accounting approach that ignores albedo impacts can significantly overestimate the climatic benefit of offsets, in particular, afforestation. In the worst case this could result in a forest offset actually contributing to worming and, in general, may reduce the environmental effectiveness of some forest offsets. Therefore a cap-and-trade system design question is whether to recognize the albedo effect into forest offset accounting frameworks. We propose that forest offset design moves toward, a "carbon-equivalent" accounting approach that aggregates the climatic impacts of sequestration and of surface albedo when evaluating forest offset projects. This change would result in climate mitigation efforts taking a more targeted geographic approach that emphasizes maintaining or increasing forest cover in the tropics, and that avoids afforestation in boreal and high-latitude temperate regions. Currently developing regional cap-and-trade systems in North America, however, give afforestation projects priority for offset consideration. By staying on the current path, efforts in these initiatives directed toward forest offsets may be inefficient or ineffective and, at worst, counterproductive, in large parts of the area they cover. Incorporating both carbon and albedo effects into policymaking will lead to more informed and effective forest offset design.