The Caspian Sea is shrinking because water is leaving its enclosed basin faster than it is being replenished. Rising temperatures and evaporation are important drivers, but river inflow, precipitation, winds, and human water use also shape its level. As the shoreline retreats, ports, fisheries, coastal communities, and wildlife habitats face growing pressure across the five countries that border the sea.
Why is the Caspian Sea shrinking?
The Caspian is an enclosed inland water body, not a sea connected to the world ocean. Its level depends on the balance among water flowing in, precipitation, evaporation, and water use within its drainage basin. A change in any of these can affect the whole sea, and several can act at once.
The recent decline is real, but the Caspian has experienced substantial rises and falls over its history. A short period of decline should not be mistaken for a perfectly steady, permanent downward trend. UNEP’s November 2024 working paper describes the drivers as complex and calls for coordinated analysis across the basin.
Warming and evaporation
As temperatures rise, evaporation increases, accelerating water loss. UNEP’s June 2026 overview identifies warming-driven evaporation as a factor hastening the decline. The World Bank’s 2026 project appraisal also attributes water loss to climate change and human water use. These sources support treating warming as an important driver, not the sole explanation for every change in level.
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River inflow and upstream conditions
Rivers supply most of the water entering the Caspian. In a 2025 speech, UNEP Executive Director Inger Andersen said the Volga provides around 80 per cent of total inflow. That dependence makes the sea especially sensitive to changes in the Volga’s discharge, which can be affected by weather and by water management upstream. Other rivers, precipitation, and winds also matter to the basin’s water balance.
Water use and diversions
Human withdrawals and diversions within the drainage basin can reduce the water reaching the sea. UNEP’s 2024 paper identifies water use and diversions alongside temperature, evaporation, precipitation, river discharge, and winds as interacting factors. The available sources do not assign a single share of the decline to each cause.
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How much has the level fallen, and will the Caspian dry up?
In her 2025 speech, Andersen reported that the Caspian level had fallen around two metres since the 1990s. That is an attributed figure from the speech, not a harmonized annual measurement for all five littoral states or a 2026 update. The sources described here do not establish one current annual rate that can be applied across the sea.
A World Bank 2026 project appraisal cites a modeled range of –1.5 to –4.1 metres in the 2050s compared with the 1995–2014 reference period. This is a range of modeled future levels, not an observation or a certain single forecast. Future conditions depend on climate and basin-wide water conditions, so it does not establish that the Caspian will dry up completely. It does indicate that substantial further decline is a serious planning concern.
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What does a retreating shoreline mean for people?
When the water’s edge moves, places built around the old shoreline can be left farther from navigable water. Shallow approaches can constrain shipping, while ports, transport links, and fishing areas may become harder or more costly to use. UNEP has identified ports and fishing villages among visibly affected places; the World Bank identifies shipping infrastructure as a particular economic challenge. These are risks and exposures, not proof that any specific port will close.
Fisheries and coastal livelihoods
Fishing communities depend on access to productive coastal waters and habitats. Retreat can alter shore and delta environments, while lower levels can compound other stresses on fisheries, including pollution, drought, overfishing, and barriers between fish and spawning rivers. UNEP reports that sturgeon are struggling to reach river deltas needed to swim upstream and breed; that difficulty should be understood alongside the other pressures on the species, not attributed to water level alone.
The World Bank appraisal reports regional sturgeon catches falling from 27,000 tons to less than 1,000 tons per annum between the late 1970s and 2007. This long-term catch history is not a measure of the effect of falling water levels by themselves. The appraisal also describes a commercial sturgeon fishing moratorium in its source context; that does not establish the rules in force today.
Costs for coastal communities
Changes to ports, fishing access, infrastructure, and local livelihoods can affect food security and income. In 2025, UNEP warned of economic costs, food-security threats, and potential displacement of millions of people. That is a stated risk, not a count of people already displaced by the retreating sea.
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What does the decline mean for Caspian wildlife?
The Caspian is important habitat for sturgeon, and UNEP describes the Caspian seal as endangered. Falling water levels can change coastal and delta habitats, but wildlife declines in the region have several interacting causes. The World Bank lists overfishing, river dewatering and dams, invasive species, agricultural pollutants, and chronic pollution associated with oil and gas activity and transport among the pressures on the ecosystem.
For fish that need to reach rivers to reproduce, water conditions and physical barriers can both matter. For seals and other wildlife, habitat change sits alongside pollution and other ecosystem stresses. It would be misleading to treat shoreline retreat as the sole cause of declines in any of these species.
What can countries do—and what remains uncertain?
The five littoral states—Azerbaijan, Iran, Kazakhstan, Russia, and Turkmenistan—share a basin-wide problem. Local measures can help communities and ecosystems adapt, but they cannot by themselves control the sea’s overall level. UNEP’s 2024 working paper calls for coordinated science on the interacting drivers; the World Bank appraisal likewise describes the need for cooperation and stronger implementation.
- Improve monitoring and shared assessment: More coordinated information on levels, inflows, climate, and water use can help distinguish basin-wide trends from local variation.
- Plan for exposed infrastructure and livelihoods: Adaptation can account for changing shorelines, port access, fisheries, and community needs without assuming that a local project can reverse the overall decline.
- Protect habitats and reduce other ecosystem pressures: Conservation efforts can address pollution, overfishing, invasive species, and barriers to river access as well as changing water conditions.
The Tehran Convention, formally the Framework Convention for the Protection of the Marine Environment of the Caspian Sea, was signed by the five littoral states in 2003 and entered into force in 2006, according to the World Bank’s 2026 appraisal. The appraisal describes monitoring and assessment frameworks and protected-area and biodiversity work, while noting the need for better implementation and cooperation.
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In a 2025 speech, UNEP described a regional 2026–2036 Action Plan as being developed, with monitoring, climate adaptation, and ecosystem protection among its aims, and called for its adoption and implementation. That account establishes the plan’s status at the time of the speech, not whether it was subsequently adopted.
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