Hurricanes Pose Substantial Risk to New England Forest Carbon Stocks

Abstract

Nature-based climate solutions are championed as a primary tool to mitigate climate change, especially in forested regions capable of storing and sequestering vast amounts of carbon. New England is one of the most heavily forested regions in the United States (>75% forested by land area), and forest carbon is a significant component of regional climate mitigation strategies. Large infrequent disturbances, such as hurricanes, are a major source of uncertainty and risk for policies that rely on forest carbon for climate mitigation, especially as climate change is projected to alter the intensity and geographic extent of hurricanes. To date, most research into disturbance impacts on forest carbon stocks has focused on fire. Here we show that a single hurricane in the region can down between 121-250 MMTCO2e or 4.6-9.4% of the total aboveground forest carbon, much greater than the carbon sequestered annually by New Englands forests (16 MMTCO2e yr-1). However, the emissions from the storms are not instantaneous; it takes approximately 19 years for the downed carbon to become a net emission, and 100 years for 90% of the downed carbon to be emitted. Using hurricane reconstructions across a range of historical and projected wind speeds, we find that an 8% and 16% increase in hurricane wind speeds leads to a 10.7 and 24.8 fold increase in the extent of high-severity damaged areas (widespread tree mortality). Increased wind speed also leads to unprecedented geographical shifts in damage; both inland and northward into heavily forested regions traditionally unaffected by hurricanes. Given that a single hurricane can emit the equivalent of 10+ years of carbon sequestered by forests in New England, the status of these forests as a durable carbon sink is uncertain. Understanding the risks to forest carbon stocks from large infrequent disturbances is necessary for decision-makers relying on forests as a nature-based climate solution.