Climate and Humans as Amplifiers of Hydro-Ecologic Change: Science and Policy Implications for Intensively Managed Landscapes

Abstract:

Climatic trends and agricultural intensification in Midwestern U.S. landscapes has contributed to hydrologic regime shifts and a cascade of changes to water quality and river ecosystems. Informing management and policy to mitigate undesired consequences requires a careful scientific analysis that includes data-based inference and conceptual/physical modeling. It also calls for a systems approach that sees beyond a single stream to the whole watershed, favoring the adoption of minimal complexity rather than highly parameterized models for scenario evaluation and comparison. Minimal complexity models can focus on key dynamic processes of the system of interest, reducing problems of model structure bias and equifinality. Here we present a comprehensive analysis of climatic, hydrologic, and ecologic trends in the Minnesota River basin, a 45,000 km² basin undergoing continuous agricultural intensification and suffering from declining water quality and aquatic biodiversity. We show that: (a) it is easy to arrive at an erroneous view of the system using traditional analyses and modeling tools; (b) even with a well-founded understanding of the key drivers and processes contributing to the problem, there are multiple pathways for minimizing/reversing environmental degradation; and (c) addressing the underlying driver of change (i.e., increased streamflows and reduced water storage due to agricultural drainage practices) by restoring a small amount of water storage in the landscape results in multiple non-linear improvements in downstream water quality. We argue that “optimization” between ecosystem services and economic considerations requires simple modeling frameworks, which include the most essential elements of the whole system and allow for evaluation of alternative management scenarios. Science-based approaches informing management and policy are urgent in this region calling for a new era of watershed management to new and accelerating stressors at the intersection of the food-water-energy-environment nexus.