Recent land use change is a substantial component of the forest carbon sink in the eastern US
Quantifying forest carbon (C) stocks and stock change within a matrix of land use and land use change is a central component of large-scale forest C monitoring and reporting practices such as prescribed by the International Panel on Climate Change’s Good Practice Guidance. Despite being suggested by such guidance, true land use accounting of forest stock emissions/transfers instead of land cover assessment (with associated C modeling) has rarely occurred across the diverse forest ecosystems and land use patterns of the eastern US. Using a region wide repeated forest inventory of the eastern US, forest C stocks and stock change by pool were examined by general land use categories (forest, agriculture, and developed) and forest cover change.
Forest C stock change was much more strongly correlated with forest land use change than forest cover change (0.38 vs 0.13). The strongest sinks of forest C were in landscapes not completely dominated by forests, even when there was some loss of forests to agricultural/developed land uses. In landscapes with large forest C stocks and/or large net increases in their stocks, land cover change assessments indicated loss of forest cover while forest land use change indicated increase of forest land use. Despite some transfers of C from forests to developed/agricultural land uses over the study’s time period, transfers of C from these land uses to forests represented a large net transfer of C (~40% of sink strength) that approached the same scale of net accumulation of C in forests remaining forests. In forests of the eastern US, land use change is a substantial component of the forest C sink strength only subordinate to that of C accumulation in forests remaining forests where their comingling with dynamic land uses enhances sink strength (i.e., management and/or recovery from past land use history).