Swiss Agriculture Also Damages Waterways

With climate heating, our waterways are also becoming increasingly warmer.

Too hot for many living creatures and simultaneously ideal for the growth of numerous algae, whose decomposition process strips waterways of vital oxygen. Fish removal and artificial aeration represent costly and labour-intensive symptom management aimed at maintaining the illusion of a natural idyll. What is urgently needed are measures that address the problems at their root.

On a hot summer's day, a plunge into a cool lake or river — for many in Switzerland the very epitome of natural idyll. Yet the idyll is only seemingly natural. Beneath the surface, something is brewing.

What the heat means for aquatic life

Last summer, fishermen and authorities responded to hundreds of emergency callouts to remove remaining fish from overheated, partially drying waterways and relocate them elsewhere. In the canton of Bern alone, there were around 200 such operations. “When water temperatures rise, the solubility of gases in water decreases — something that can also be observed in the formation of bubbles when boiling water,” explains Michael Casanova, water protection expert at Pro Natura. “When oxygen saturation in a body of water decreases while temperature rises, this poses an existential threat to many species that depend on cool, oxygen-rich water. Trout and grayling experience heat stress above 20°C; above 25°C conditions become critical and the fish suffer organ failure.”

What this has to do with over-fertilisation

Algae, on the other hand, thrive at high temperatures. “When the surrounding region is also heavily fertilized and slurry is spread, this leads to a true algal plague in warmed waters,” says Casanova. In standing bodies of water, the water then begins to putrefy, drawing even more oxygen out of the ecosystem until it dies — as occurred in Lake Baldegg, Lake Hallwil, and Lake Sempach. “Such clinically dead ecosystems have therefore been artificially supplied with oxygen and kept alive for decades using expensive aeration systems,” the expert explains.
In warm lakes, where toxic blue-green algae also proliferate massively under these conditions, swimming bans must even be imposed to protect people and domestic animals — as was the case, for example, at Lake Neuchâtel and Lake Greifen last year. Aquatic organisms, however, cannot leave their habitat and are largely defenceless against these severe impairments.

Measures for Climate Adaptation

In order to preserve aquatic habitats, rivers and lakes in Switzerland must be supported in adapting to the climate crisis and the associated heat and water scarcity. Three things are particularly important for this:

1. It is of central importance thatriverbanks and lakeshores are planted in a nature-friendly and site-appropriate manner. Riparian vegetation retains water in the soil both during flooding and during dry periods, making the body of water more resilient to high temperatures. The shading of the water surface and the evaporation of water through leaves have a cooling effect on water bodies and are thus the most natural means of protecting them from overheating.
2. It is important todrastically reduce nutrient inputs from agricultureand to maintain buffer zones around water bodies in order to keep algal growth within limits.
3. Theresidual water volumes of hydropower must be adjusted. When new concessions are granted and existing usage rights are renewed, the residual water volume must be increasedespecially during the hot season. When more water flows, the overall warming decreases.

More on the topic of climate change and environmental and nature conservation.

You can help all animals and our planet with compassion. Choose compassion on your plate and in your glass. Go vegan.