Recognizing Agricultural Headwaters as Critical Ecosystems

Abstract

Agricultural headwaters are positioned at the interface between terrestrial and aquatic ecosystems and, therefore, at the margins of scientific disciplines. They are deemed devoid of biodiversity and too polluted by ecologists, overlooked by hydrologists, and are perceived as a nuisance by landowners and water authorities. While agricultural streams are widespread and represent a major habitat in terms of stream length, they remain understudied and thereby undervalued. Agricultural headwater streams are significantly modified and polluted but at the same time are the critical linkages among land, air, and water ecosystems. They exhibit the largest variation in streamflow, water quality, and greenhouse gas emission with cascading effects on the entire stream networks, yet they are underrepresented in monitoring, remediation, and restoration. Therefore, we call for more intense efforts to characterize and understand the inherent variability and sensitivity of these ecosystems to global change drivers through scientific and regulatory monitoring and to improve their ecosystem conditions and functions through purposeful and evidence-based remediation.

How to Achieve a 50% Reduction in Nutrient Losses From Agricultural Catchments Under Different Climate Trajectories?

“…When estimating cost-effectiveness other ecosystem services enabled by SM such as flood control, biodiversity improvement, and social benefits should be taken into account (Hambäck et al, 2023). Stream mitigation can achieve a higher cost-effectiveness compared to measures strictly focusing on one ecosystem service or water quality problem (Bieroza et al, 2024;Djodjic et al, 2022). For example, SM is the only tested measure that also significantly impacted discharge dynamics, which is promising for mitigating floods and droughts under climate change (Figure 4).…”