Improving kettle holes as habitat and reproduction areas for amphibians – a case study in organic farms in north-eastern Germany

Kettle holes are found in young moraine landscapes and serve as an important habitat for amphibians. The loss of amphibians has been dramatic in recent decades, mainly because of the increase in land use intensity and deterioration of habitats e.g., kettle holes in agricultural landscapes. We monitored amphibian species on three organically managed farms in north-eastern Germany to get an overview of their occurrence and proof of reproduction to develop effective protection strategies. From 2016 to 2020, we investigated 50 kettle holes in cultivated fields. In 2018, we implemented the nature conservation measure ‘cutting back dense wooded belts’ in six of these kettle holes. Here, we focused on seven species considering four highly endangered species. We found six to seven species in up to 17 kettle holes in the 44 kettle holes without the measure ‘cutting back dense wooded belts’. Bombina bombina occurred at the most kettle holes (57%). The number of kettle holes where amphibians reproduced differed strongly. On average, at least one species reproduced at 58% of the kettle holes. Many kettle holes become overgrown with negative effects for amphibians due to the reduction in solar irradiation and higher water consumption. The nature conservation measure increased the number of species on average from two to four and the number of species with reproduction from one to three. It is one of more than 100 measures in the ‘Farming for Biodiversity’ project that farmers can choose to receive a nature conservation certificate, which can be used for marketing purposes.