Background
Freshwaters are particularly vulnerable to climate change for many reasons. The publication "Rote Liste der gefährdeten Biotoptypen" (Red List of endangered habitat types), which is published by the Federal Agency for Nature Conservation at approximately ten-year intervals, states in the latest version of 2017 that almost two thirds of the habitat types occurring in Germany are endangered. Particularly high levels of endangerment are found in nitrogen-sensitive peatlands and nutrient-poor lakes and small bodies of water against the background of land-use influences. Lakes are also suitable indicators of the effects of climate change. Smaller water bodies in particular react quickly to temperature rises and dry periods and can provide valuable information for adapted and modified decisions on action or management.
Current research results indicate that the global temperature increase is already having a measurable impact on lakes in Germany (as well as globally). Added to this are stress factors from the last few dry years. Unfortunately, the Intergovernmental Panel on Climate Change (IPCC) still focuses primarily on the effects of climate change on oceans and the cryosphere in relation to "climate and water ecosystems". However, the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), the largest research centre for inland waters in Germany, summarises in its 2019 annual research report: "Due to climate change, more and more water bodies will dry up at least temporarily, and many lakes will shrink or disappear permanently. This trend not only endangers drinking water reserves and important ecosystems: Drying waters play an important role in the global carbon cycle, as they can release CO2 and other climate-relevant gases and thus further intensify climate change. The consequences for biodiversity under and over water are considerable, especially since many aquatic and amphibian species are already classified as endangered or threatened with extinction.