Ecosystem Services of Kettle Holes in Agricultural Landscapes

Kettle holes are small water bodies of glacial origin which mostly occur in agricultural landscapes. They provide numerous ecosystem services (ES), but their supply may be negatively affected by agricultural management. We conducted a literature review to identify which ES are supplied by kettle holes and to analyze feedbacks with agricultural management. Taking Germany as a test case, we also analyzed how kettle holes are addressed in policy documents and for which ES they are regulated. This was done to identify the societal value officially associated with kettle holes. The literature review found eight ES attributed to kettle holes, of which hydrological cycle and flood control, chemical condition of freshwaters, nursery populations and habitats and biotic remediation of wastes were addressed most often. In contrast, only the provision of habitat service was addressed in German policy documents related to kettle holes. We identified types of agricultural management that negatively affected the supply of ES by kettle holes, in particular artificial drainage, high levels of pesticide and fertilizer application, and management where tillage and erosion result in elevated sediment inputs. Additionally, climate change may lead to an increased drying up of kettle holes. Based on our finding, we conclude that the intensity of agricultural management around kettle holes threatens the supply of all ES while only the service of providing habitats for biodiversity is addressed in German policy regulations. Further regulation is required to induce agricultural management change towards a conservation of all ES supplied by kettle holes.