The Caspian Sea Is Shrinking: Causes, Ecological Impact, and Why It Matters

Climate change, declining river inflows, and human activities are causing the Caspian Sea to shrink rapidly, threatening biodiversity, regional economies, and millions of livelihoods

Caspian Sea Shrinking Raises Global Environmental Concerns

The Caspian Sea, the world's largest inland water body, is shrinking at an alarming rate due to a combination of climate change and human activities. Scientists warn that the continued decline in water levels could severely impact biodiversity, fisheries, regional trade, and the livelihoods of millions of people living along its coastline.

A June 2026 study titled "The Shrinking Caspian Sea: Eco-Hydrological Responses to Human and Climate Pressures" identifies declining river inflows and increased evaporation caused by rising global temperatures as the primary reasons behind the shrinking sea.

Since the mid-1990s, the Caspian Sea has lost approximately 5.5% of its surface area, equivalent to around 630 cubic kilometres of water.

What Is the Caspian Sea?

Although called a sea, the Caspian is technically the world's largest landlocked lake because it has no natural connection to any ocean.

Located between Europe and Asia, it covers approximately 371,000 square kilometres and has a coastline stretching about 6,819 kilometres.

The Caspian Sea is bordered by five countries:

• Azerbaijan

• Iran

• Kazakhstan

• Russia

• Turkmenistan

Around 130 rivers flow into the Caspian, with Russia's Volga River contributing nearly 80% of the total freshwater inflow.

Why Is the Caspian Sea Ecologically Important?

The Caspian Sea is one of the world's most unique inland ecosystems.

Because it is isolated from the oceans, nearly 80% of its aquatic species are endemic, meaning they are found nowhere else on Earth.

Some of its most famous species include:

• Caspian Seal

• Beluga Sturgeon

• Several species of sturgeon that produce the majority of the world's caviar

The shallow northern Caspian serves as an important breeding ground for fish, supports wetlands, and lies along major migratory bird routes connecting Europe, Asia and Africa.

The sea also helps regulate regional temperature and moisture because water leaves the basin only through evaporation.

Economic Importance of the Caspian Sea

Apart from its ecological value, the Caspian Sea is strategically important.

It contains:

• Vast oil reserves

• Natural gas deposits

• Offshore energy infrastructure

• Major shipping routes connecting Europe and Asia

Its ports play an important role in:

• Russia's trade

• Central Asian transport networks

• Iran's maritime connectivity

• China's Belt and Road Initiative

• India's International North-South Transport Corridor (INSTC)

Why Is the Caspian Sea Shrinking?

Scientists attribute the shrinking Caspian Sea to both human activities and climate change.

1. Declining Freshwater Inflow

The largest contributor is the reduction in freshwater entering the sea, especially through the Volga River.

Major causes include:

• Construction of dams

• Reservoir projects

• River diversion

• Excessive withdrawal of water for irrigation

These activities have significantly reduced the volume of water reaching the Caspian.

2. Increased Evaporation Due to Climate Change

Climate change has intensified evaporation across the region.

Between 1979 and 2015, the average local surface air temperature increased by approximately 1°C.

Combined with changing wind patterns, this has accelerated evaporation far beyond the amount of water entering through rivers.

Unlike oceans, the Caspian cannot receive additional water from elsewhere because it is completely enclosed.

Major Consequences of the Shrinking Caspian Sea

Threat to Biodiversity

The falling water level threatens many endangered species.

Beluga Sturgeon

The Beluga Sturgeon migrates into freshwater rivers for breeding.

The Caspian Sea once produced nearly 90% of the world's black caviar, but declining water levels and pollution are disrupting breeding cycles and pushing these fish closer to extinction.

Caspian Seal

The endangered Caspian Seal is losing its shallow coastal habitat as shorelines retreat.

Declining Water Quality

Scientists have observed increasing chlorophyll-a concentrations, indicating higher algal growth caused by:

• Warmer water

• Nutrient enrichment

This raises the risk of:

• Harmful algal blooms

• Poor water quality

• Reduced oxygen levels

Impact on Coastal Communities

Thousands of families depend on the Caspian Sea for:

• Fishing

• Employment

• Food security

Shrinking water levels are reducing fish stocks and threatening traditional livelihoods.

New Land and Toxic Dust Storms

Experts estimate that if the sea level falls by 5 metres, nearly 20% of the Caspian Sea could become dry land.

The exposed seabed may release:

• Toxic salts

• Dust particles

These could create environmental and public health hazards similar to those experienced around the Aral Sea.

Trade and Transport Challenges

Lower water levels make navigation increasingly difficult.

Reduced navigability may disrupt:

• Shipping routes

• Energy transportation

• Regional trade between Europe and Asia

This could affect major international transport corridors.

The Tehran Convention

To protect the Caspian Sea, the five coastal nations signed the Framework Convention for the Protection of the Marine Environment of the Caspian Sea, commonly known as the Tehran Convention, in 2003.

Supported by the United Nations, it remains the only legally binding regional agreement dedicated to protecting the Caspian Sea.

The Convention is based on:

• Precautionary Principle

• Polluter Pays Principle

• Information sharing and cooperation

Its objectives include:

• Preventing pollution

• Protecting biodiversity

• Restoring marine ecosystems

Four Protocols Under the Tehran Convention

The Convention includes four important protocols:

• Aktau Protocol – Oil pollution response

• Moscow Protocol – Land-based pollution control

• Ashgabat Protocol – Biodiversity conservation

• Environmental Impact Assessment Protocol

COP29 Declaration on Caspian Sea Water Level Decline

Recognising that climate change has become the biggest challenge facing the Caspian Sea, the five littoral nations adopted the Declaration on Strengthening Cooperation to Address the Caspian Sea Water Level Decline during COP29 in 2024.

The declaration calls for:

• Joint scientific research

• Coordinated monitoring

• Regional cooperation

• Establishment of a working group to study declining water levels

What Needs to Be Done?

Experts believe reversing the crisis requires stronger regional cooperation.

Priority actions include:

• Better management of the Volga River basin

• Reducing excessive water withdrawals

• Regulating dam construction

• Restoring degraded habitats

• Conserving endangered species

• Promoting sustainable fisheries

• Strengthening scientific data sharing among the five coastal countries

Key Facts About the Caspian Sea

• World's largest inland water body

• Covers approximately 371,000 sq km

• Coastline of 6,819 km

• Bordered by Azerbaijan, Iran, Kazakhstan, Russia and Turkmenistan

• Receives water from around 130 rivers

• Volga River supplies nearly 80% of freshwater inflow

• Lost 5.5% of its surface area since the mid-1990s

• Around 80% of aquatic species are endemic