Agricultural systems are experiencing increasing demands as we strive to increase food and feed production, produce fuel and fiber, and maintain ecosystem services. Moving forward, it will be necessary that we understand how varying ecological and societal drivers of change may mitigate or augment current stress on agricultural land. The Yahara Watershed, an agricultural and urbanizing watershed spanning 1,345 km2 in Southern Wisconsin with a chain of five lakes, exemplifies many of the current challenges regarding the impact and interaction of climate change, land-use/land cover, and nutrient management in the Midwest US. To evaluate the impacts of increased perennial grass cover and reduced crop nutrient applications on ecosystem services in a changing climate, we generated 30 scenarios using an agroecosystem model, Agro-IBIS. Agro-IBIS simulates energy, water, carbon, and nutrient balance by modeling biophysical and biogeochemical processes at a 220 m by 220 m scale. Scenario development focused on quantifying the tradeoffs associated with a transition from annual row crops to perennial grasses (10%, 25%, 50% transition) within the Yahara watershed, under varying manure and fertilizer applications (10%, 25%, 50% reduction) and climate change. In order to incorporate both spatial and temporal analysis, all scenarios were projected to the year 2070.
Results/Conclusions
For each of the 30 generated scenarios, watershed level averages of key ecosystem services were analyzed based on decadal averages, with percent change calculated between the following timespans: 2004-2013 and 2061-2070. As eutrophication is a long-term problem, emphasis is placed on water quality metrics – phosphorus yield and nitrate leaching. Based on our findings, inaction leads to further environmental degradation – with phosphorus yield increasing by 13%, 7%, and 23% under a baseline climate, warmer and drier climate, and a warmer and wetter climate, respectively. However, by increasing the percentage of cropland dedicated to perennials – water quality improves as phosphorus yield decreases between 10-22%. A combined approach incorporating both an incremental increase in proportion of land dedicated to perennials and a decrease in manure and fertilizer application rates results in the greatest mitigating potential, leading to about a 50% reduction in phosphorus yield. Nitrate leaching results followed similar trends. Across all scenarios, soil carbon content remained relatively constant for the next 50 years with changes ranging from -/+ 5%. Crop yield increased despite reductions in manure and fertilizer application. Our research emphasis the large-scale management changes required to promote ecosystem services under a changing climate.