Impact of afforestation with Loblolly Pines (Pinus taeda L.) in the Southeastern US on regional and global climate

Native southern US 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, we examined the local and remote consequences of biofuel feedstock expansion on climate and hydrology using a global climate model, the NCAR Community Earth System Model version 4 (CCSM4). We considered a plausible DOE biofuel feedstock goal by afforesting 19 million acres of C4 grasslands in the Southeastern US with an optimized Loblolly plant functional type. Changes in sensible and latent heat fluxes were related to increased surface roughness, reduced bare-ground evaporation, and changes in stomatal conductance. These mechanisms led to a 1°C cooling over the Southeastern US during the summer; in winter, we observed a cooling of up to 0.3°C between 40-60°N, a weakened Aleutian Low, and a wetter Australia. A weakened Aleutian Low shifted the North Pacific storm track poleward in our future Loblolly scenarios. These local and global impacts suggest that biophysical feedbacks need to be considered when evaluating the benefits of bioenergy feedstock production.