Saturday, June 21, 2008

Journal looks at forests, carbon sequestration, and climate…

The June 13 issue of the journal Science features an extensive series of articles on Forests in Flux. In “Managing Forests for Climate Change Mitigation,” Josep Canadell and Michael Raupach suggest three strategies to mitigate carbon emissions through forestry: reforestation to increase forested land area, bolstering the carbon density of existing forests, and expanding the use of forest products that sustainably replace emissions from fossil-fuels.

“Forests currently absorb billions of tons of carbon dioxide globally every year, an economic subsidy worth hundreds of billions of dollars if an equivalent sink had to be created,” write Canadell and Raupach. “Concerns about the permanency of forest carbon stocks, difficulties in quantifying stock changes, and the threat of environmental and socioeconomic impacts of large-scale reforestation programs have limited the uptake of forestry activities in climate policies [but] with political will and the involvement of tropical regions, forests can contribute to climate change protection.”

In “Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests,” Gordon B. Bonan discusses feedback mechanisms between forests and climate--the carbon cycle, the water cycle, surface energy fluxes, and vegetation dynamics--as well as human alteration of the biosphere. He argues that improved modeling of these interactions will aid in the development of land use policies to mitigate climate change. “These policies must recognize the multitude of forest influences, their competing effects on climate, their different spatial and temporal scales, and their long-term effectiveness and sustainability in a changing climate,” Bonan writes.

The fate of forests is increasingly determined by concesssionary agreements with extractive industries and the demand for commodities produced on forest lands, and climate change and rapid economic growth further complicate effective forest management. In “Changing Governance of the World’s Forests,” Arun Agrawal, Ashwini Chhatre, and Rebecca Hardin argue that understanding the factors that lead to effective governance--rather than explicit ownership of forest land--will be critical to addressing future governance of forest resources.

“The goal of forest conservation has historically not been met when in conflict with land use changes driven by the demand for food, fuel, and profit,” they write. “It is necessary to recognize and advocate for better governance of forests more strongly given the importance of forests in meeting basic human needs in the future, making resources available for livelihoods and development, maintaining ecosystems and biodiversity, and addressing climate change mitigation and adaptation goals.”

In “Beyond Deforestation: Restoring Forests and Ecosystem Services on Degraded Lands,” Robin Chazdon argues that the complexities involved in reforestation require a case-by-case analysis to determine whether natural regeneration or some form of human-guided reforestation is the best way to proceed. Chazdon says that depending on the state of the forest and its soil, some forest regeneration may benefit from human intervention, but that many secondary forests have proven that nature works better.

Much of the interest in reforestation is currently based on carbon storage and climate mitigation, and Chazdon cautions against quick solutions: “Fast-growing, short-lived species with low-density wood are favored by many reforestation projects designed to provide carbon offsets, but long-term carbon sequestration is promoted by growth of long-lived, slow-growing tree species with dense wood and slow turnover of woody tissues.”

Finally, Chazdon explains that new forests are not a solution to deforestation of existing forests: “Plantations and restored forests can improve ecosystem services and enhance biodiversity conservation, but will not match the composition and structure of the original forest cover.”