Climate change and disappearing forests eliminate one of nature’s great freshwater purification systems
Drinking water quality will be affected by the disappearance of forests due to climate change, according to a report new study from the Helmholtz Center for Environmental Research (UFZ) in Germany. Experts point out that the damaging effects of climate change are particularly evident in Germany’s largest reservoir, the Rappbode reservoir, which supplies around a million people with drinking water.
Between 2015 and 2020, long periods of drought severely weakened the tree population in the Harz region, where parasites such as bark beetles had already caused considerable damage. The added stress of the drought was too much for the trees, which were quickly wiped out.
In the last four years, the Rappbode basin, characterized by conifers, mainly spruces, has lost more than 50% of its forest. “This massive forest retreat is advancing rapidly and is dramatic. This will have consequences for the drinking water reservoir”, explains Professor Michael Rode, a hydrologist at the UFZ.
Forests are necessary for good water quality because they filter water and retain nutrients. Water with fewer nutrients, such as nitrogen or phosphorus compounds, is easier to treat. This hampers algae growth, which makes treating drinking water in treatment plants more profitable and easier.
The UFZ team began investigating the effects of climate-induced deforestation on the water quality of the reservoir. They did this by collecting environmental data over a period of more than ten years, which they fed into a mathematical model to estimate climate-related effects on nutrient balance in the catchment area. This allowed simulating the effects of deforestation on projected water quality for 2035.
Forests are necessary for good water quality because they filter water and retain nutrients
For a projected deforestation of up to 80%, the Rappbode Dam will experience an 85% increase in dissolved phosphorus concentration and a more than 120% increase in nitrogen concentration in just 15 years. The result will be an increase in diatoms (microscopic algae) of more than 80% and an increase in green algae of more than 200% in the dam.
To reduce this excess of nutrients, the solution is to continue promoting reforestation projects with drought-resistant tree species, say the researchers.
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