ADVERTISEMENTThe world’s largest landlocked water body is shrinking at a rate that could critically endanger an iconic seal species, put coastal communities at risk and release toxic dust, new research reveals.
Water levels in the Caspian Sea – which is bordered by Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan – are falling as rising temperatures mean more water is evaporating than flowing in.
Even if global warming is limited to below 2°C, it is likely that the Caspian Sea will drop by 5 to 10 m, shaving 112,000 km² off its current size of 387,000 km². Left unchecked, climate change could see water levels drop by as much as 21 m by 2100.
Researchers at the UK’s University of Leeds have now mapped what that means for the region’s biodiversity and human infrastructure. With many of the Caspian Sea’s most important areas located in shallow water, they say that urgent action is required to protect species and coastal communities.
The animals that depend on the Caspian Sea staying big
Caspian seals are found exclusively in the brackish Caspian Sea, where they have adapted to wide swings in temperature.
Between January and March, the seals give birth to their white-coated pups on the ice in the northern Caspian Sea. But even a 5m decline could reduce the area of this habitat by up to 81 per cent, according to the new study, putting huge pressure on an already reduced population.
The Caspian seal was listed as endangered by the International Union for the Conservation of Nature (IUCN) in 2008, due to a wide range of stressors, including oil and gas drilling, shipping, and the already evident signs of habitat alteration from climate change.
The shrinking sea will also make the seals’ haul-out sites – areas where they rest on land – inaccessible. Though receding water levels may create some new islands, it is not yet known if they will be suitable alternatives.
The diminutive seals are the obvious ‘poster children’ of the Caspian Sea’s plight, but many other species are threatened by its retreat, and the environmental impacts are far-reaching.
The Caspian Basin was once home to the world’s most diverse array of sturgeons, an ancient family of large fish. All five Caspian sturgeon species which spawn in rivers are critically endangered due to overfishing for their meat and caviar.
Now, the shallower parts of the sea that sturgeons inhabit in summer and autumn are facing a potential reduction in size of up to 45 per cent, which may stop the fish reaching their spawning sites in the Volga, Ural and other inflowing rivers.
The Caspian Sea is also a globally important habitat for birds migrating between Europe, Asia and Africa. These birds rely on coastal lagoons and reed beds for resting, shelter and food during their migrations, but such habitats are vulnerable to loss as waters recede.
In total, a 10m decline in water levels would wipe out four out of 10 ecosystem types unique to the Caspian Sea. Marine protected zones, safeguarded for their biodiversity, would almost completely vanish – except for a very small amount of water in Kazakhstan.
What are the human implications, and how can people help?
More than 15 million people live around the coasts of the five Caspian countries, and they rely on the sea for fishing, shipping and trade. In the northern Caspian, the findings show that some settlements, ports and industrial facilities could end up being stranded far from new shorelines.
Ports in Baku (Azerbaijan), Anzali (Iran), and Aktau (Kazakhstan) are expected to see increases in distance to shore of 1 km or more, while Turkmenbashi (Turkmenistan) and Lagan (a planned site in Russia) could see that distance grow by 16 km and 115 km.
ADVERTISEMENTCoastal communities in the north are likely to be hit hardest as income from fishing disappears. And climate change could serve an economic double whammy, as loss of water from the Caspian would alter the regional climate – leading to lower rainfall across central Asia, making agricultural work harder.
There are also pressing health concerns. Once exposed, the dry seabed is likely to release dust containing industrial contaminants and salt, posing serious threats to human health. It could be a similar story to the Aral Sea – where salty dust storms from the dried-up sea bed continue to make people sick.
Given the manifold risks climate change poses to the Caspian Sea, time is of the essence.
“Some Caspian Sea level decline appears unavoidable, even with action to reduce global greenhouse gas emissions,” says Dr Simon Goodman from the School of Biology at the University of Leeds, who supervised the research.
ADVERTISEMENT“However, with the anticipated effects unfolding over a few decades, it should be possible to find ways to protect biodiversity while safeguarding human interests and wellbeing.
“That might sound like a long timescale, but, given the immense political, legislative and logistical challenges involved, it is advisable to start action as soon as possible to give the best chance of success.”
Welcoming the study’s important warnings, Dr Elchin Mamedov from the Ministry of Ecology and Natural Resources in Azerbaijan says it shows “the need to enhance regional and international cooperation to help manage the impacts.”
