The Caspian Sea, the largest inland body of water in the world, is shrinking dramatically and has reached its lowest recorded point of 29 metres below sea level. It is bordered by five littoral states, such as Azerbaijan, Iran, Russia, Turkmenistan, and Kazakhstan, covering an expansive area of 386,400 square kilometres. Renowned for its rich biodiversity, it hosts nearly 850 animal and 500 plant species1. Beyond its biological diversity, the Caspian Sea boasts abundant natural resources, including oil and natural gas. It is estimated that the Caspian Sea holds approximately 48 billion barrels of oil and 292 trillion cubic metres of natural gas2.
Unfortunately, the Caspian Sea faces an explicit risk of desertification, posing a significant threat to its marine flora and fauna, as well as to the socio-economic situation in the coastal states. The main causes of the reduction of the Caspian Sea can primarily be related to the impacts of climate change and anthropogenic factors, including the regulation of river inflows, desalination, and hydrocarbon contamination.
The alarming decline in the water level of the Caspian Sea began in the early 20th century. Between 1930 and 1941, it experienced a significant annual decrease, averaging 14.7 cm. From 1941 to 1978, the Caspian Sea continued to shrink, albeit at a slower pace, decreasing by approximately 3 cm per year. It reached its lowest level in 1977 at -29 m. Interestingly, contrary to predictions of further decline, the water level started to rise between 1978 and 1995, increasing by around 15 cm per year. However, this trend did not last long, as the water level began to decline again from 1995 onwards3. Since then, it has been shrinking by an average of 7 cm per year. In 2023, it exceeded its lowest level, reaching 29.20 m below sea level4.
Caspian Sea Level (CSL) Change: 1840-2015
If this trend continues, particularly in the northern part of the Caspian Sea, bordered by Kazakhstan, it faces the risk of disappearance5. It is estimated that 70 percent of the water area vulnerable to desiccation is situated in Kazakhstan6. The northern region is especially at risk due to its shallowest depth, containing only 1/100 of the total water volume with an average depth of 4.5 m. A negative trend was already observed last summer in the city of Aktau, which lies on the Caspian Sea’s shores. On June 8, 2023, a state of emergency was declared in the port city due to the reduction of the Caspian Sea level7. Following the declaration of the state of emergency, Kazakhstan’s Minister of Ecology, Zulfiya Suleimenova, stated that the environmental situation in the Caspian Sea is complicated, and the negative consequences primarily impact Kazakhstan’s sector8.
Why is the Caspian Sea shrinking?
The primary cause of the environmental issues in the Caspian Sea is related to climate change. Due to climate change, the amount of precipitation over the Caspian Sea has decreased and the evaporation rate has risen. Since 1979, the average surface temperature over the Caspian Sea has increased by about 1 degree Celsius per year9. Furthermore, climate change has affected the rate of river inflows that feed the Caspian Sea. With about 130 rivers providing the bulk of the annual drainage in the water body, the main inflow comes from the Volga River, accounting for about 80 percent of the volume of the Caspian Sea. Low precipitation on the inflowing rivers results in a reduction in the Caspian Sea level10. As a result of these factors, in 2010, the level of the Caspian Sea decreased by 31-44 cm11.
However, the reason for the decrease in the Caspian Sea is not limited to natural causes. Anthropogenic factors resulting from human activities have significantly influenced the water level. A notable example is the reduction of discharges from the Caspian rivers. The industrialization conducted by the Soviet Union in the 1930s played a pivotal role in shaping the condition of the water body12. Numerous reservoirs were constructed on the inflowing rivers to maintain the operation of hydroelectric power industries. It was during this period that the Caspian Sea’s level began to decrease. The construction of dams on the Volga River in the 1950s disrupted the flow of water and sturgeon into the body of water. Between 1956 and 1969, the Caspian Sea’s volume decreased by 25 km3 annually. It is estimated that if the amount of water inflowing from the Caspian rivers had not been reduced, the current level of the Caspian Sea would have been more than 1-1.5 m higher13. Currently, there are about 8 dams on the Volga River that significantly hinder the discharge of water into the Caspian Sea14.
Anthropogenic damage from river inflows extends beyond the water level reduction, as these rivers also significantly contaminate the Caspian Sea. Annually, they carry 75,000 tons of oil products to the water body, accounting for half of its total hydrocarbon contamination. More than 95% of this contamination originates from the Volga River alone. The other half of hydrocarbon pollution is linked to the extraction of hydrocarbons in the Caspian Sea itself. Given the vast amount of hydrocarbon resources in the body of water and their large-scale production by littoral states, it is unsurprising that hydrocarbon contamination poses a significant problem.
In the Kazakh sector alone, an estimated 8,000 tons of oil leak into the Caspian Sea annually15. Hydrocarbon extraction has accelerated the Caspian Sea level’s decline through three main ways. Firstly, as hydrocarbon production releases greenhouse gases, it contributes to decreased precipitation over the water body, leading to drying out of the area. Secondly, hydrocarbon extraction contributes to soil erosion, which further leads to the decline of the water level. Finally, the extraction process itself significantly pollutes the water, constituting the main negative influence of hydrocarbon extraction on the Caspian Sea16.
The decrease in the water level of the Caspian Sea can also be linked to desalination efforts undertaken by Kazakhstan, Turkmenistan, Azerbaijan and Iran. These littoral states rely on desalination from the Caspian Sea due to water scarcity in their respective territories. Given the relatively low cost of desalination from the water body, these states are interested in extracting large amounts of water. Moreover, desalinated water is used not only for human consumption and agriculture but also for the production of green hydrogen. Notably, it takes five metric tons of desalinated water to produce one megawatt of energy. Kazakhstan has several projects in collaboration with EU countries for hydrogen production and importation. While such projects would certainly contribute to environmental improvement in Europe by reducing greenhouse gas emissions, they may lead to negative consequences for the Caspian Sea, accelerating its water level decline17.
What are the consequences of the water level decline in the Caspian Sea?
The consequences of the Caspian Sea’s shrinking primarily affect its marine life, particularly the Caspian seal population. Their numbers have significantly declined since 1950, with the most recent sharp decline observed in 2022 on the Russian coast of the Caspian Sea, where the bodies of 2,500 dead seals were found18. Their mass extinction led to their inclusion in the International Union for Conservation of Nature’s red list of threatened species, as well as in the Red Books of the coastal states.
The decline in the seal population can be attributed both to abovementioned natural and anthropogenic factors. Low precipitation and high evaporation have diminished thickness and seasonal duration of the ice sheets, which are crucial for the seal reproductive processes. Consequently, seals have to change their habitats to other areas, which negatively affects their breeding. Moreover, new areas might be contaminated by hydrocarbon extraction, leading to the accumulation of toxicants in seal bodies. As a result, seals lose their resistance to diseases and environmental stress19.
Furthermore, the negative consequences of a decrease in the water level may affect residents of city ports who consume desalinated water from the Caspian Sea. In January 2023, due to unfavourable weather conditions, the water intake canal in the port city of Aktau froze. Consequently, the canal was unable to desalinate water and left city residents without water for more than 10 days20. This incident shows that port city residents in coastal countries will be left without water if the Caspian Sea continues to shrink. In addition, the economies of the littoral states would suffer as a result of water level decline, affecting shipping and the maritime transportation industry. Given the large profits generated by trading routes in the water body, desertification would cause serious damage to the region's economy.
Problems in the Caspian water management
The consequences of the reduction in the level of the Caspian Sea might be more devastating due to ineffective water management. Despite negative indicators in the state of the Caspian Sea being observed since the beginning of the 20th century, the first joint measures aimed at addressing environmental issues were taken only in 2003. In particular, five littoral states reached an agreement for the first time and signed the Convention for the Protection of the Marine Environment of the Caspian Sea, which came into effect in 2006. The Convention contains four protocols, such as Regional Preparedness, Response and Co-Operation in combating Oil Pollution Incidents, Protection of the Caspian Sea against Pollution from Land based Sources and Activities, Conservation of Biological Diversity and Environmental Impact Assessment in a Transboundary Context.
However, the process of designing and ratifying environmental institutions for the Caspian Sea has been prolonged, hindering the implementation of measures to mitigate environmental issues. Moreover, only the first two protocols have entered into force, while the others have not been ratified by either Russia or Iran21. Their reluctance to ratify the protocols may be explained by their geopolitical and economic interests in the region. They prioritize environmental concerns if they align with their interests. For instance, to halt the construction of the Trans-Caspian Pipeline, Russia and Iran invoked the Convention on the Legal Status, which obliges the parties to abide by environmental standards when constructing pipelines in the water body22. In addition, Russia’s reluctance to regulate the inflow from the Volga River is driven by its economic interests. Therefore, there is still no management of the river inflows in the Caspian Sea, despite this being the main factor contributing to reducing the water level.
Another issue with water management stems from legal uncertainty regarding the delimitation of the Caspian Sea. The littoral states have divergent preferences on the division of the water body. For instance, Kazakhstan and Azerbaijan advocate for a partition that would ensure the sovereignty of the coastal states over the divided territories. Kazakhstan, in particular, favours treating the Caspian Sea as an enclosed sea and therefore prefers the division of the seabed and resources along the median line principle. According to Azerbaijan’s position, the Caspian Sea is a border lake that should be completely divided along the median line. On the other hand, Iran supports the condominium approach, where the water body is divided equally and jointly managed by all coastal states. Without this arrangement, Iran will have the smallest share in the water body23.
Despite disagreements over the delimitation of the water body, the littoral states signed the Convention on the Legal Status of the Caspian Sea in 2018 in Aktau. According to the Convention, the Caspian Sea is divided into three zones: territorial waters, fishery zones, and the common area. The littoral states have sovereignty over territorial waters, which extend from the coast up to 15 nautical miles, and fishery zones, which extend further 10 nautical miles. The area beyond fishery zones is intended for common use. However, the delimitation of the seabed area remains unresolved. States can delimit their respective seabed sectors only by concluding bilateral or multilateral agreements24. Additionally, the Convention has not yet been ratified by Iran, rendering it invalid25.
Overall, the environmental degradation of the Caspian Sea can be attributed to global warming, anthropogenic factors, and weak water management. All these factors contribute to the reduction of the Caspian Sea level, which may have far-reaching consequences for biodiversity and the socio-economic situation of the littoral states. While the immediate consequences may not be explicit at the moment, the situation may worsen in the near future. To avoid repeating the fate of the Aral Sea, it is necessary to take timely measures to regulate the water resources of the Caspian Sea.
What can be done to prevent the threat of desertification in the Caspian Sea?
The first important step is to implement the Integrated Water Resource Management (IWRM). The implementation of the IWRM strategies should start with the development of action plans to address the reducing level of the Caspian Sea. This can be achieved if all littoral states come together and take comprehensive measures to minimize the impact of all anthropogenic factors on the water level.
As river inflows play the most significant role in reducing the level of the Caspian Sea, their management needs to be addressed first. Russia, where the main Caspian rivers are located, must maintain sustainable irrigation levels in these inflowing rivers and monitor the quantity and quality of discharged water. The management of desalination should involve cooperation among riparian states and the establishment of an agreement on an acceptable desalination rate that would minimize the impact on the decrease in water level. Regarding the management of hydrocarbon contamination, this issue has already been addressed in the Aktau Protocol. However, effective monitoring and enforcement mechanisms are necessary to implement the objectives of the agreement.
Furthermore, achieving the delimitation of the seabed area of the Caspian Sea is crucial. Water management in the Caspian Sea will not succeed without the full division of the water body. The littoral states should bear responsibility for the ecological state of their respective sectors. As the accomplishment of these measures depends on the cooperation and consensus between the five littoral states, they should prioritize environmental protection of the Caspian Sea over economic goals.
Finally, the engagement of the international community in managing the environmental issue of the Caspian Sea is an important step to prevent the threat of desertification. Considering the global economic significance of the Caspian Sea, the consequences of the reduction of water levels will extend beyond the littoral states. Therefore, developed states must provide scientific expertise and technology to regulate the level of the Caspian Sea and prevent adverse consequences.