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The Caspian Sea, seen here from the in­ter­na­tional space sta­tion ISS, is the largest lake in the world. Its wa­ter levels are fall­ing due to cli­mate change.

© NASA | Scott Kelly | The Caspian Sea, seen here from the in­ter­na­tional space sta­tion ISS, is the largest lake in the world. Its wa­ter levels are fall­ing due to cli­mate change.

Cli­mate crisis is caus­ing lakes to shrink

Au­thors of sci­entific art­icle call for more at­ten­tion to re­gions with fall­ing wa­ter levels

Cli­mate change is im­pact­ing not only the oceans, but also large in­land lakes. As the world’s largest lake, the Caspian Sea is a per­fect ex­ample of how a body of wa­ter can and will change. In an art­icle in the Nature journal Communications Earth & Environment, Dr. Mat­thias Prange of MARUM – Cen­ter for Mar­ine En­vir­on­mental Sci­ences at the Uni­versity of Bre­men, and his col­leagues dis­cuss the pos­sible eco­lo­gical, polit­ical and eco­nomic con­sequences, as well as vi­able solu­tions.

While global sea levels are rising due to the cli­mate crisis and threat­en­ing near-coastal in­fra­struc­tures, higher tem­per­at­ures in other areas are hav­ing ex­actly the op­pos­ite ef­fect. The wa­ter levels are fall­ing and also caus­ing massive prob­lems. Al­though the con­sequences are equally ser­i­ous, however, de­clin­ing wa­ter levels are re­ceiv­ing less at­ten­tion ac­cord­ing to Mat­thias Prange, Thomas Wilke of the Jus­tus Liebig Uni­versity in Gießen, and Frank P. Wessel­ingh of the Uni­versity of Utrecht and the Nat­uralis Biod­iversity Cen­ter Leiden (The Neth­er­lands).

“The Caspian Sea can be viewed as rep­res­ent­at­ive of many other lakes in the world. Many people are not even aware that an in­land lake is dra­mat­ic­ally shrink­ing due to cli­mate change, as our mod­els in­dic­ate,” says Mat­thias Prange. The re­port of the In­ter­gov­ern­mental Panel on Cli­mate Change (IPCC) also failed to men­tion lakes, and dis­reg­arded the so­cial, polit­ical and eco­nomic con­sequences of global warm­ing on the af­fected re­gions. “This has to change. We need more stud­ies and a bet­ter un­der­stand­ing of the con­sequences of global warm­ing in this re­gion.” The goal must be to raise aware­ness of the con­sequences of cli­mate change for in­land seas and lakes so that ap­pro­pri­ate strategies can be de­veloped, in­clud­ing ap­proaches for other large lakes and re­gions fa­cing sim­ilar chal­lenges.

Be­cause of its size (it is the largest lake in the world) and be­cause of its re­l­at­ively high sa­lin­ity of about one per cent, which is about one-third of the salt con­cen­tra­tion in the oceans, the Caspian has been named a ‘Sea’. Its largest in­flow is the Volga River and it has no nat­ural con­nec­tion to the ocean. The wa­ter level is de­term­ined by the pro­por­tional in­flu­ences of in­flow, pre­cip­it­a­tion and evap­or­a­tion. Global warm­ing is caus­ing in­creased evap­or­a­tion, which res­ults in a de­clin­ing wa­ter level.

The Caspian Sea is an im­port­ant re­gional wa­ter reser­voir and, des­pite its salt con­tent, a bio­lo­gical and com­mer­cial cen­ter. It is bounded by Kaza­kh­stan, Turk­menistan, Iran, Azerbaijan and Rus­sia. De­pend­ing on the de­gree of global warm­ing in the fu­ture, the wa­ter level could fall by 9 to 18 meters dur­ing this cen­tury. “This would af­fect not only the biod­iversity, vari­ous spe­cies, and hab­it­ats that would dis­ap­pear. The eco­nom­ies of all the bor­der­ing coun­tries would be im­pacted, in­clud­ing har­bors, fish­er­ies and fish farm­ing.” For this reason, the au­thors ar­gue that in the fu­ture the Caspian Sea should be used as an ex­ample in sci­entific re­search to as­sess the vul­ner­ab­il­ity of cer­tain re­gions to fall­ing wa­ter levels. Be­cause no na­tion can solve the res­ult­ing con­flicts alone, they pro­pose a global task force to de­velop and co­ordin­ate strategies. The art­icle sug­gests that “in­ter­na­tional cli­mate funds” could of­fer a pos­sib­il­ity for fin­an­cing pro­jects and ad­apt­a­tion meas­ures if changes in the lake level are at­trib­uted to cli­mate change.

  • Mat­thias Prange, Thomas Wilke, Frank P. Wessel­ingh: The other side of sea level change.  Com­mu­nic­a­tions Earth & En­vir­on­ment 2020. DOI: 10.1038/s43247-020-00075-6

MARUM 2020

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