Opposite effect: sea level rises – lake level falls

Opposite effect
Sea levels rise – lake levels fall

In many regions of the world, sea levels are threatened to rise as a result of climate change. But on land the problem with the water is completely different – the level of the largest lake on earth could even sink by almost 20 meters in the coming decades. With dramatic consequences.

The water level of many lakes could fall considerably in the coming decades as a result of rising temperatures – with dramatic effects on the environment, economy and politics. Researchers from Bremen and Giessen as well as the Netherlands illustrate this using the example of the Caspian Sea. The water level of the largest lake on earth could have dropped 9 to 18 meters by the end of the century.

“This aspect of climate change – sinking water levels in lakes – could be just as devastating as the rise in global sea levels,” the scientists write in the journal “Communications Earth & Environment”. They demand immediate action, as the problem has so far received far too little attention from the scientific and political side.

Caspian Sea bigger than Germany – still

The Caspian Sea lies between the very edge of Eastern Europe and the Middle East and Central Asia. The neighboring countries include Russia, Kazakhstan, Iran and Azerbaijan. The lake covers 371,000 square kilometers and is thus slightly larger than Germany (357,000 square kilometers). The largest tributary is the Volga, the salt lake has no natural connection to the sea. The water level of the lake is determined by precipitation, inflow and evaporation. With climate change, evaporation increases and the water level falls – a few centimeters a year since the 1990s.

By 2100, the drop will have added up to 9 to 18 meters – with medium to high carbon dioxide emissions. “If the North Sea dropped two or three meters, access to ports like Rotterdam, Hamburg and London would be impeded. Fishing boats and giant containers would have problems alike, and all countries on the North Sea would have a big problem,” explains Frank Wesselingh from the university Utrecht in a communication. “We’re talking about a decrease of no less than nine meters – in the best case.”

As the water level falls, the area of ​​the lake shrinks by 23 to 34 percent. As a result, the habitat of numerous animal and plant species would disappear or its size and quality would be impaired. An example: if the water level falls, the ice surface shrinks in winter – the nursery of the threatened Caspian seal. The animals would also lose valuable food sources.

Influence on fishing and tourism

The people around the lake are also likely to suffer from the shrinking because their fishing areas are becoming smaller, the problem of water shortages in many regions is exacerbated or recreation and tourism are impaired. Political tensions are also to be expected in an already unstable region because borders, water access rights or fishing grounds would have to be renegotiated, the researchers continue.

“The Caspian Sea is representative of many other lakes in the world. According to our models, inland water is shrinking dramatically due to climate change,” says Matthias Prange from the Marum Center for Marine Environmental Sciences at the University of Bremen. The problem does not receive enough attention in the reports of the Intergovernmental Panel on Climate Change either. “That has to change, we need more studies and more knowledge about the effects of global warming in this region.”

The scientists propose the establishment of a global working group to develop and coordinate strategies to develop adaptation strategies for the Caspian Sea and other large lakes and regions facing similar challenges.

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