Forests around the world sequester more than 2 billion tonnes of carbon each year—enough to offset about one-fifth of the carbon dioxide that humans emit annually.
Any reduction in forests’ capacity to absorb CO₂ will make it harder to slow and/or reverse the accumulation of CO₂ in the atmosphere. The UNFCCC Paris Accord (2015), the United States Mid-Century Strategy for Deep Decarbonization (2016), and virtually every other major policy prescription for climate change recommends aggressive efforts to protect and enhance forest carbon sinks around the world.
As shown in the diagram below, though, carbon sequestration is one of several ways in which forests affect climate change. For example, altering the size, health, location, and composition of forests can also influence climate by changing albedo (the proportion of sunlight that’s reflected—rather than absorbed—when it hits the earth’s surface) or by increasing or decreasing evapotranspiration (the process by which plants transfer terrestrial moisture into the atmosphere; an important element in cloud formation). Although comparatively little is known about these kinds of non-carbon factors, research suggests that their potential impact on climate could be similar in scale to the impact from fluctuations in forest carbon stocks. Likewise, very little is known about the extent to which these non-carbon factors shape the effectiveness of climate-motivated measures to promote carbon stocking.
In conjunction with leading experts, CATF is working to identify the most important information gaps in our understanding of how forests influence climate and to develop a research agenda for filling those gaps. The integrated assessment of forests’ key climate influences (e.g., carbon flux, but also albedo, evapotranspiration, emissions of biogenic aerosols, and other non-carbon factors) will support the development of climate-optimal forest management strategies and forest-related climate policy.
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