Green-Moist-Cool Index
It is not only Germany’s major cities that are heat hotspots; there are also extensive heat landscapes. This is shown by a new scientific study by the ECONICS INSTITUTE.
The newly founded think tank for ecosystems is publishing a Green-Wet-Cool Index for Germany for the first time and presenting it in partnership with NABU (Nature and Biodiversity Conservation Union).
The study was first published as a preprint and submitted to an international journal: Yojana Adhikari, Pierre L. Ibisch, Peter Wohlleben, Anselm Schneider, Daniel Johnson (2025). Working landscapes under climate change need to be green, moist, and cool—a case study of Germany.
Key findings: Land use is responsible for almost a fifth of temperature differences, and where it is greener and cooler, there is even more precipitation – and not only in mountainous regions. Green vegetation, water, and relative coolness form a central triangular relationship that enables ecosystems to live and function.
The new data confirms the well-known fact that urban areas and industrial zones in particular heat up disproportionately on hot days. It also shows that large areas of heat-prone landscapes have developed even in regions with structurally poor agriculture. Without trees, hedges, and copses, i.e., without adequate amounts of natural vegetation, the soil dries out, heats up, and reinforces a vicious cycle. As a result, plants grow less well, leading to the threat of water shortages and crop losses. In contrast, regions with forests, wetlands, many hedges, and permanent grassland are significantly cooler. They store and evaporate water and even promote precipitation.
The positive >>green-wet-cool<< triad is therefore self-reinforcing. Positive feedback loops mean that green vegetation can thrive better in cooler, wetter areas, which in turn retain water better and can cool themselves even at higher temperatures. However, such feedback loops also apply in places where it becomes critically hot and dry: the living conditions for green plants deteriorate, and they can no longer cool and humidify their environment. Heat, drought, and the weakening of green vegetation fuel each other, which can lead to a downward spiral that reduces the performance of ecosystems. This then has consequences for all ecosystem services that are of interest to humans. These include, not least, the natural climate protection effect of nature: in drying out and weakened forests or moors, the stored carbon is released, which in turn further drives climate change.
The study by the new ECONICS INSTITUTE on the productivity and performance of nature in Germany allows for a novel view of the landscape based on international approaches and satellite image data.
Nature is not a green backdrop that we can simply visit and admire for recreation and relaxation, nor is it a warehouse from which we can take whatever we need for our economic activities. Rather, nature consists of complex systems that literally work to exist and function. Through their physical work, they also create the basis for our existence.
The scientific paper (in English) on the >>Green-Wet-Cool Index<< is currently under review and is available as a preprint.
The summary report can be downloaded hiere (in German):