Forests, Climate, and Public Policy: A 500-Year Interdisciplinary Odyssey

In 1888, the question of whether it is "worth while to go on planting trees for their climatic effects" was debated and answered with an expression of "the uselessness of it." It was part of a multi-century debate that began with the widespread deforestation in the European settlement of North America and culminated with advocating afforestation of the Great Plains to promote rainfall. While conservationists and foresters argued for the influences of forests on climate, meteorologists expressed skepticism and dismissed the premise. Modern climate sciences tell us that forests do indeed influence climate through exchanges of momentum, energy, water, and chemicals with the atmosphere and that anthropogenic land use and land-cover change do alter climate. It is thought that historical deforestation in temperate latitudes has cooled climate because of an increase in planetary albedo, countered by warming due to a release of carbon from the land to the atmosphere. Many forests emit biogenic volatile organic compounds that form aerosols and cool climate. Reforestation, afforestation, avoided deforestation, and biofuels have been advocated to mitigate anthropogenic carbon dioxide emissions. However, forest ecosystems affect climate through a myriad of processes, and the net climate benefit of forests may be less than their carbon mitigation potential. Moreover, the viability of the terrestrial carbon sink over the next 100 years and longer is highly uncertain. Anthropogenic climate change is a complex scientific problem that poses difficult political solutions. Planting trees has climate benefits, but tree planting is not a simple climate policy to implement. Destroying the word’s forests makes mitigating climate change more difficult, but the mitigation effects of forests may be less than realized so even more forest preservation is required. Like our predecessors, we still have much to learn about forests and climate. The sharp debate about forests and climate in the early history of the United States highlights the difficulty of communicating across the biological and physical sciences. Study of Earth’s future requires a broad interdisciplinary vision of our environment and our role in shaping the environment. We still lack a comprehensive framework to study climate, forests, humans, and their interactions so as to shape public policy.