COS 101-6 - Hurricanes pose a major risk to New England forest carbon

Abstract: Current and proposed climate adaption policy for New England states relies heavily on carbon sequestered in forests to serve as a nature-based climate solution. New England is among the most heavily forested regions in the United States (80% of total land cover), and these forests serve as a critical carbon sink, with an annual aboveground forest carbon (AFC) flux of -15.8 million metric tons of CO₂ equivalence (MMTCO2e). However, New England’s forests are vulnerable to natural disturbances, primarily forest pests and hurricanes. In the 20^th century alone, the region was affected by 10 major hurricanes, with the greatest being The Great New England Hurricane of 1938, which downed nearly 70% of the trees in large parts of central New England.

In this study, we seek to determine the level of risk posed to New England forest carbon from hurricane disturbances. Specifically, we 1. modeled the paths and strengths of past hurricanes and potential future hurricanes using the Hurrecon and Expos models informed by National Hurricane Center data; 2. created a spatial product of the forested landscape by estimating the aboveground biomass of hardwood and softwood trees of various height classifications using the The Big Data, Mapping, and Analytics Platform (BIGMAP); and 3. spatially estimated the impact that a hurricane would have on AFC based on the modern-day forest composition and projected hurricane wind-damage.

We found that, given modern-day forest composition, a single New England hurricane could down 121-250 MMTCO2e of AFC. At the current carbon flux of New England’s forests, it would take 7.5-10.6 years to regenerate the AFC downed by a single hurricane. Southern New England states (RI, MA, and CT) are more vulnerable to hurricane-induced forest damage. However, if hurricane windspeeds increase, northern New England states (ME, NH, and VT) could see a drastic increase in hurricane damage, where an 8% increase in hurricane windspeeds would lead to an estimated 195% more downed AFC in those states. Furthermore, an 8% increase in windspeeds leads to a 900% increase in the forested area experiencing severe wind damage ( >70% downed AFC). While New England forests currently serve as a carbon sink, the long-term effects that ecological disturbances (along with anthropogenic forces on the landscape) will have on the composition and carbon of New England forests for the remainder of the 21^st century remain uncertain; however, ecological disturbances such as hurricanes, pose a real and significant risk.