From model outputs to conservation action: Prioritizing locations for implementing agricultural best management practices in a Midwestern watershed

Abstract

Many ecologically significant Midwestern rivers are heavily impacted by agriculture yet retain high value for conservation of biodiversity. To address these concerns, watershed managers promote conservation practices (e.g., use of cover crops). Yet taking action to promote implementation of these practices in a cost-effective manner across a watershed is difficult because we rarely know where practices will be most effective, or how much of a benefit will accrue as the result of implementation of a given practice. To improve targeting of conservation practice implementation in locations most beneficial to biodiversity, we propose using a flexible approach assessing fields across a watershed for contributions towards ecological outcomes. We focused on Michigan's Paw Paw River Watershed, where key concerns for biodiversity include reduced infiltration and groundwater recharge that lead to pronounced low and high flow periods, and reduced water quality due to high sediment loads. We used outputs from several existing models to identify and prioritize the agricultural fields where conservation practices will have the greatest reduction in threats to biodiversity, including estimates of the input to groundwater and reduction in sedimentation. We tested the usefulness of our approach using four scenarios for implementation of six practices that vary in terms of the concentration of the practices in areas recommended by the models. Estimates of groundwater recharge under these scenarios were compared to recharge under simulated, “historic” placement scenarios based on USDA Natural Resources Conservation Service (NRCS) data for applied conservation practices in the same watershed. Collectively across the six practices, the prioritized scenarios provided an increase in groundwater recharge of between 23% and 36% over the historic scenario. Results for sediment reduction were more variable, but prioritized scenarios suggested a doubling of benefit can be obtained by focusing on agricultural lands predicted to contribute the highest sediment volumes. To maximize the benefits of aggregating practices, we identified subbasins of the watershed for direct outreach to landowners based on a ranking of potential, cumulative downstream conservation benefits and on opportunity factors. As a result of this process, prioritized areas and estimates of groundwater recharge are now informing implementation of conservation practices in the Paw Paw River Watershed, an approach applicable across the region.