Local and remote climate impacts from expansion of woody biomass for bioenergy feedstock in the southeastern United States

Many efforts have been taken to find energy alternatives to reduce anthropogenic influences on climate. Recent studies have shown that using land for bioenergy plantations may be more cost effective and provide a greater potential for CO₂ abatement than using land for carbon sequestration. Native southern U.S. pines(i.e., loblolly) have excellent potential as bioenergy feedstocks. However, the land-cover change due to expansion of biofuels may impact climate through biophysical feedbacks. Here, the authors access the local and remote consequences of greater forest management and biofuel feedstock expansion on climate and hydrology using a global climate model, the NCAR Community Climate System Model, version 4 (CCSM4). The authors examine a plausible U.S. Department of Energy (DOE) biofuel feedstock goal by afforesting 50 million acres of C₄ grasslands in the southeastern United States with an optimized loblolly plant functional type. Changes in sensible and latent heat fluxes are related to increased surface roughness, reduced bareground evaporation, and changes in stomatal conductance. In the coupled simulations, these mechanisms lead to a 1°C cooling, higher atmospheric stability, and a more shallow planetary boundary layer over the southeastern United States during the summer; in winter, a cooling of up to 0.25°C between 40° and 60°N,a weakened Aleutian low, and a wetter Australia occurs. A weakened Aleutian low shifts the North Pacific storm track poleward in the future loblolly scenarios. These local and global impacts suggest that biophysical feedbacks need to be considered when evaluating the benefits of bioenergy feedstock production.