Sea level rise threatens the lives of hundreds of millions of people in low-lying coastal areas, but many people living around lakes and inland seas may soon be wishing for a modest rise in water level. A new study reveals how close we are to catastrophe in the world's largest inland waterway, the Caspian Sea, with lessons for those dependent on other vulnerable bodies of water.
Called a sea because of its immense size and salinity (averaging a third that of the oceans), the Caspian is technically a lake. Those who live nearby depend on it for fishing, transportation, and species-rich wetlands.
Since the 1990s, the level of the Sea has been falling a few centimeters a year, much faster than the world's oceans are rising. A study in Communications Earth and Environment predicts that without major interventions this reduction will accelerate, and describes the likely consequences. Moreover, the paper argues, the problem is widespread across endorheic lakes (those without an outflow.
A warming climate means endorheic lakes evaporate faster. For some this is compensated by increased rainfall in their catchment areas, but in other cases reduced precipitation adds to the problems. Meanwhile irrigation often steals more of what does fall.
Dr Frank Wesselingh of Utrecht University and co-authors calculate these factors will cause the Caspian Sea to fall by 9-18 meters (30-60 feet) by 2100, double previous estimates; 23-34 percent of the surface area will be lost.
Environmental collapse can be a trigger for warfare, for example initiating the Syrian Civil War. With five often hostile nations bordering the Caspian, the risk of conflict over shrinking resources is high.
"If the North Sea would drop two or three meters, access to ports like Rotterdam, Hamburg and London would be impeded. Fishing boats and container giants alike would struggle, and all the countries on the North Sea would have a huge problem", Wesselingh said in a statement. "Here, we are talking about a decrease of no less than nine meters – in the best case scenario.”
The danger of a Caspian Sea catastrophe shouldn't be hard to spot. East of the Caspian lies the Aral Sea – or at least it once did. Diversion of the rivers that once fed the Aral to feed immense cotton farms by the Soviet Union caused it to lose 90 percent of its water, leading to eerie photographs of ships marooned hundreds of kilometers from the nearest water.
Even without human activity, endorheic lakes can be vulnerable. Lake Chad once rivaled the Caspian Sea. Only the last stages of its 99.9 percent vanishing act are humanity’s fault; most of the earlier decline happened naturally in a few centuries.