Sensitivity to climate change of land use and management patterns optimized for efficient mitigation of nutrient pollution

Beginning in the mid-1990s, re-eutrophication has reemerged as severe problems in Lake Erie. Controlling non-point source (NPS) nutrient pollution from cropland, especially dissolved reactive phosphorus (DRP), is the key to restore water quality in Lake Erie. To address NPS pollution, previous studies have analyzed the effectiveness of alternative spatially optimal land use and management strategies (represented as agricultural conservation practices (CPs)). However, few studies considered both strategies and have analyzed and compared their sensitivity to expected changes in temperature and precipitation due to climate change and increased greenhouse gas concentrations. In this study, we evaluated impacts of climatic change on the economic efficiency of these strategies for DRP abatement, using an integrated modeling approach that includes a watershed model, an economic valuation component, and a spatial optimization model. A series of climate projections representing relatively high greenhouse gas emission scenarios was developed for the western Lake Erie basin to drive the watershed model. We found that performance of solutions optimized for current climate was degraded significantly under projected future climate conditions. In terms of robustness of individual strategies, CPs alone were more robust to climate change than land use change alone or together with CPs, but relying on CPs alone fails to achieve a high (> 71%) DRP reduction target. A combination of CPs and land use changes was required to achieve policy goals for DRP reductions (targeted at ~ 78%). Our results point to the need for future spatial optimization studies and planning to consider adaptive capacity of conservation actions under a changing climate.