Estimating the Effects of Vegetation Change on Carbon Sequestration and the Relative Impacts of Albedo in the Mid-Atlantic USA

The Mid-Atlantic Region (MAR) in the United States has gone through considerable shifts in its surface vegetative properties from the 1900s to the present day. During the 1900s, the MAR land-surface was composed of 38% Broadleaf Deciduous Forest (BDF), 32% crops, with evergreen trees and grasses covering the remaining areas. By 2000, the MAR experienced increases of BDF and reached up to 44%, cropland decreased to 17%, while evergreen and grass coverage remained roughly constant. With the observed vegetation changes in the MAR, the corresponding land-use conversion of around 500,000 km² has led to substantial changes in surface radiative properties, surface energy budgets, and amounts of carbon assimilation. Such shifts in the MAR reveal an interplay between two contrasting aspects of global warming: the positive effect of sequestering more carbon by adding trees, and the counteracting increase in surface temperature caused by a reduction in albedo. By estimating the albedo's relative effects on carbon sequestration using a common currency such as CO2 equivalent, we can determine the proportion of sequestered carbon that was offset by the decrease in albedo due to afforestation. While these calculations are typically conducted on a global scale, we focus on the MAR to examine the implications of land-use changes specifically for policy implementation. We use albedo and net ecosystem-exchange data outputs from multiple climate models in the study, allowing us to assess the differences in the climate models' representation of this change and providing a more comprehensive understanding of the uncertainty range for the global warming potential due to afforestation. Additionally, we also conduct a perturbation experiment using a climate model to quantify the biophysical impact of vegetation change, thereby assessing its effects on surface energy and radiative fluxes.