Land use legacies of the Ohio River Basin: Using a spatially explicit land use change model to assess past and future impacts on aquatic resources

Land uses and their legacies are a major driver of human impacts on the environment. Decision makers have recognized that the legacies of land-use activities continue to influence ecosystems, particularly aquatic ones, for decades or centuries. The main objectives of this paper are to develop land use legacy maps to (1) assess historical and future (predicted) shifts in dominant land use classes (urban, agriculture, forest) in the Ohio River Basin (ORB), and (2) determine the past and future location of catchments in the ORB exceeding critical land use thresholds (10% and 38% urban and agricultural use of catchment respectively) for water quality and other aquatic resources. Our land use legacy simulations show that approximately 80% of the ORB has remained as agriculture (～37%), forest (～34%), urban (～7%) and other classes (～2%) from 1930 to 1990. Within the remainder of landscape, agriculture to forest (～16%) and agriculture to urban (～1.5%) transitions were the most common land use changes between 1930 and 1990. Our forecast model shows that approximately 94% of the ORB will remain as forest (～47.46%), agriculture (～35.77%), urban (～8.84%) and other classes (～2.07%) between 2000 and 2050. 1.44% and 1.37% of the ORB is predicted to transition from forest to urban and agriculture to urban between 2000 and 2050, respectively. Our results also demonstrate that 13% and 74% of the catchments in the ORB already exceeded critical urban and agricultural land use thresholds in 1930, respectively. We predict that 37% of catchments in the ORB will have exceeded critical urban land use thresholds by 2050, whereas the proportion of catchments to exceed critical agricultural use will decrease to 45%.