[Un article de The Conversation écrit par Simon Goodman – Lecturer in Evolutionary Biology, University of Leeds]
Climate change is at the origin of this spectacular decline in the largest closed sea in the world. Located on the border between Europe and Central Asia, the Caspian Sea is surrounded by Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan, and supports about 15 million people.
The Caspian is a fisheries, navigation and oil and gas production center, and its geopolitical importance is increasing, since it is at the crossroads of the interests of the great world powers. As the sea becomes in depth, governments face the crucial challenge of maintaining industries and their livelihoods, while protecting the unique ecosystems that support them.
I have been going to the Caspian for over twenty years, to collaborate with local researchers in order to study the Caspian seal, a unique and threatened species, and support its conservation. In the 2000s, the extreme northeast of the sea formed a mosaic of reedlières, vasières and shallows shallow teeming with life, offering habitats with Frai fish, migratory birds and tens of thousands of seals gathered there in spring to mute.
Today, these wild and remote places where we captured seals for satellite follow -up studies have become dry land, in transition to the desert as the sea retires, and the same story is repeated for other wetlands around the sea. This experience echoes that of the coastal communities, which see, year after year, the water is moving away from their cities, their fisheries and their cities, ports, leaving the infrastructure stranded on newly dried land, and residents worried about the future.
A sea set back
Caspian sea level has always fluctuated, but the extent of recent changes is unprecedented. Since the beginning of this century, the water level has dropped by about 6 cm per year, with falls up to 30 cm per year since 2020. In July 2025, Russian scientists announced that the sea had descended below the previous minimum level recorded since the start of instrumental measures.
During the XXe Century, variations were due to a combination of natural factors and humans by humans for agriculture and industry, but today, global warming is the main engine of decline. It may seem inconceivable that a mass of water as large as the Caspian is threatened, but in a warmer climate, the water flow entering the sea by rivers and precipitation decreases, and it is now exceeded by the increase in evaporation on the surface of the sea.
Even if global warming is limited to the target of 2 ° C set by the Paris Agreement, the water level should drop up to ten meters from 2010 coast. With the current trajectory of global greenhouse gas emissions, the decline could reach 18 meters, or approximately the height of a six -story building.
As the north of the Caspian is shallow – a large part only reaches five meters deep – small level decreases cause immense surface losses. In recent research, my colleagues and I have shown that a ten -meter optimistic decline would discover 112,000 square kilometers of seabed – an area larger than Iceland.
What is at stake
The ecological consequences would be dramatic. Four of the ten types of unique Caspian sea ecosystems would disappear completely. The Caspian seal, a threatened species, could lose up to 81 % of its current reproduction habitat, and the Caspian sturgeon would lose access to essential frai areas.
As during the Aral Sea disaster, where another huge central Asian lake has almost completely disappeared, toxic dust from the exposed seabed would be released, with serious health risks.
Millions of people are likely to be moved as the sea retires, or to be confronted with highly degraded living conditions. The only link in the sea with the world maritime network involves the Volga delta (which flows into the Caspian), then by a upstream channel connecting the donation, offering connections to the Black Sea, the Mediterranean and other river systems. But the Volga is already faced with a reduction in its depth.
Ports like Aktau in Kazakhstan and Bakou in Azerbaijan must be dredged simply to be able to continue to work. Likewise, oil and gas companies must dig long channels to their offshore facilities in the north of the Caspian.
The costs already incurred to protect human interests amount to billions of dollars, and they will only increase. The Caspian is at the heart of the “median corridor”, a commercial route connecting China to Europe. As the water level drops, maritime cargoes must be reduced, costs are increasing, and cities and infrastructure may be isolated, dozens or even hundreds of kilometers from the sea.
A race against the clock
Caspian riparian countries must adapt, moving ports and digging new navigation paths. But these measures may conflict with the conservation objectives. For example, it is planned to flirt with a new large navigation channel through the “threshold of the Ural” in the north of the Caspian. But this is an important area for the reproduction of seals, their migration and their diet, and it will be a vital zone for the adaptation of ecosystems as the sea retires.
As the rate of change is so rapid, the protected areas at fixed borders may become obsolete. What is needed is an integrated and prospective approach to establish a plan on the scale of the whole region. If the areas where ecosystems will have to adapt to climate change are mapped and protected now, political planners and decision -makers will be better able to ensure that infrastructure projects avoid or minimize new damage.
To do this, the countries of the Caspian will have to invest in monitoring biodiversity and in planning expertise, while coordinating their actions between five different countries with various priorities. Caspian countries already recognize existential risks and have started to conclude intergovernmental agreements to deal with the crisis. But the pace of decline could exceed that of political cooperation.
The ecological, climatic and geopolitical importance of the Caspian Sea means that its fate largely exceeds its retardant shores. It constitutes an essential case study on the way in which climate change transforms the large expanses of interior water around the world, from Lake Titicaca (between Peru and Bolivia) to Lake Chad (on the border between Niger, Nigeria, Cameroon and Chad). The question is whether governments will be able to act quickly enough to protect both the populations and the nature of this rapidly changing sea.
With an unwavering passion for local news, Christopher leads our editorial team with integrity and dedication. With over 20 years’ experience, he is the backbone of Wouldsayso, ensuring that we stay true to our mission to inform.
