Less forest, less drinking water
If the average global temperature rises by more than three degrees Celsius over the next 200 years, Siberia, Canada, Amazonia and eastern China could lose up to two-thirds of their current forest area. In addition, problems with the drinking water supply in West Africa, southern Europe and in the east of the United States are likely to worsen.
Even a lower temperature increase of less than two Kelvin will cause the forests in regions that are currently still densely vegetated to shrink by thirty percent, predict scientists led by Marko Scholze from the University of Bristol. They compared 52 current computer simulations of climate change in order to calculate possible risks for globally important ecosystems. Their summary confirms frequently mentioned consequences of global warming, such as rapid changes in extreme environmental events.
For example, rising temperatures are favoring more frequent droughts in the north-eastern Amazon region, which in turn increases the risk of fire there. As a result, the forest is disappearing, which triggers more severe flooding and erosion during episodic heavy rainfall. Similar developments also apply to the Mediterranean region. Beyond three Kelvin of heating, current carbon dioxide sinks could also become plentiful sources because their biomass is more rapidly microbially degraded or destroyed by fire - ultimately leading to further amplification of the greenhouse effect, the researchers warn.
However, some regions can also potentially expect an increase in forest area: Trees find improved growth conditions above all in the savannah areas of Africa and in today's tundra regions of North America and Eurasia.
