Globally, forest loss not only releases a large amount of carbon to the atmosphere, but it also significantly diminishes a major pathway for carbon removal long into the future ( Houghton and Nassikas, 2018). In addition, forests are responsible for much of the carbon removal by terrestrial ecosystems which together remove 29% of annual CO 2 emissions (∼11.5 PgC Friedlingstein et al., 2019). Adding the carbon in soils, forests contain over 800 PgC, almost as much as is currently stored in the atmosphere ( Pan et al., 2013). Forests sequester large quantities of carbon of the 450–650 Pg of carbon stored in vegetation ( IPCC, 2013), over 360 Pg is in forest vegetation ( Pan et al., 2013). Protection, expansion, and improved management of the world’s forests represent some of the most promising natural solutions to the problem of keeping global warming below 1.5–2 degrees ( Griscom et al., 2017 Roe et al., 2019). The importance of forests for both global climate change mitigation and local adaptation by human and non-human species is not adequately captured by current carbon-centric metrics, particularly in the context of future climate warming.įailure to stabilize climate is in itself a large threat to biodiversity already at risk from deforestation. Locally at all latitudes, forest biophysical impacts far outweigh CO 2 effects, promoting local climate stability by reducing extreme temperatures in all seasons and times of day. Beyond 50°N large scale deforestation leads to a net global cooling due to the dominance of biophysical processes (particularly increased albedo) over warming from CO 2 released. In the mid-latitudes up to 50°N, deforestation leads to modest net global warming as warming from released forest carbon outweighs a small opposing biophysical cooling. From the tropics to a point between 30°N and 40°N, biophysical cooling by standing forests is both local and global, adding to the global cooling effect of CO 2 sequestered by forests. We find that tropical deforestation leads to strong net global warming as a result of both CO 2 and biophysical effects.

We then combine published data on the biophysical effects of deforestation on climate by latitude with a new analysis of the climate impact of the CO 2 in forest aboveground biomass by latitude to quantitatively assess how these processes combine to shape local and global climate. Here we review the biophysical mechanisms by which forests influence climate and synthesize recent work on the biophysical climate forcing of forests across latitudes. Evaluating the net impact is complicated by the disparate spatio-temporal scales at which they operate. The net climate impact of carbon effects and biophysical effects determines outcomes for forest and agricultural species as well as the humans who depend on them. However, when forest cover, structure and composition change, shifts in biophysical processes (the water and energy balances) may enhance or diminish the climate effects of carbon released from forest aboveground biomass. These factors are used to assess the impacts of different drivers of deforestation and forest degradation as well as alternative forest management. 3The Alliance of Bioversity International and the International Center for Tropical Agriculture, Cali, ColombiaĬlimate policy has thus far focused solely on carbon stocks and sequestration to evaluate the potential of forests to mitigate global warming.2The Woodwell Climate Research Center, Falmouth, MA, United States.

1Department of Environmental Sciences, University of Virginia, Charlottesville, VA, United States.Deborah Lawrence 1* Michael Coe 2 Wayne Walker 2 Louis Verchot 3 Karen Vandecar 1

Biophysical hydrological processes