The war in Ukraine is making a growing environmental crisis in the Caspian Sea worse, claims Zaur Shiriyev, a scholar at the Carnegie Russia Eurasia Center. The Aral Sea is already almost entirely gone, but now global warming has seen the Caspian Sea shrink by a third and that has caused alarm in the bordering countries.

In early July, a sudden mass die-off of fish by Azerbaijan's coast raised concerns about the environmental impact of Russia's military activities in the Caspian Sea, particularly its cruise missile strikes on Ukraine. This coincided with a significant Russian missile attack that allegedly used Kalibr cruise missiles launched from the Caspian Sea.

Azerbaijan's biodiversity agency attributed the fish deaths to warmer water and lower oxygen levels. However, military activity can cause pollution and disrupt marine life, and Russia’s increased military operations in the Caspian Sea have heightened fears of environmental damage, Shiriyev said in a note. Similar incidents have occurred in the past, including mass seal deaths on Kazakhstan's and Russia's coasts, with some attributing these to environmental pollution potentially linked to military activities.

In March–May 2022, shortly after the full-scale invasion of Ukraine, an unprecedented number of dead seals were found along Kazakhstan’s Mangistau region coast. In November 2022, about 170 seal carcasses were found on Kazakhstan’s shores -- the largest die-off in years -- followed by thousands more on Russia’s Dagestan coast and hundreds on Turkmenistan’s Gyzylsuw Island a month later.

While Russia attributed the Dagestan incident to natural causes, Kazakhstan's February 2023 investigation linked its seal deaths to pneumonia and viral infections exacerbated by environmental pollution, without ruling out potential links to missile fuel pollution.

Pollution in the Caspian Sea is typically attributed to the oil and gas industry, but the renewed use of Soviet-era Kh-55 and other missiles by Russian bombers over the Caspian Sea has led to concerns that toxic substances from missile fuel are harming the marine ecosystem. These substances, including detsilin, a fuel ingredient, can be highly toxic, affecting the central nervous systems of marine life and accumulating in the food chain, Shiriyev reports.

“Such fears date back to 2022, when a Russian journalist claimed that Caspian fauna were dying due to poisonous substances from Soviet-era Kh-55 and other missiles fired by Tu-160 and Tu-95 bombers flying over the Caspian Sea. Since old missiles are often used, some fail and crash into the sea. These defective missiles leak substances like detsilin, a toxic fuel whose ingredients suppress central nervous systems. Such substances can poison creatures, build up in the food chain, and disrupt crucial habitats,” Shiriyev said.

The environmental degradation in the Caspian Sea, worsened by military activities, is difficult to quantify but could have severe long-term impacts. The noise and shock from missile launches and military exercises further disrupt the marine environment, affecting migration, breeding, and feeding patterns of marine species.

The growing environmental concerns also raise questions about potential violations of international agreements. The 2018 Caspian Convention, which promotes the peaceful use of the sea, lacks provisions for demilitarisation. However, the Framework Convention for the Protection of the Marine Environment of the Caspian Sea (Tehran Convention) could be invoked if evidence of significant environmental harm caused by military activities were found. Such a claim would require formal complaint and international arbitration if not resolved diplomatically, says Shiriyev.

“It’s unlikely that any Caspian state will complain publicly about pollution, but they are more vocal about falling water levels. The sea gets four fifths of its water from Russia’s Volga River, an inflow that has been shrinking annually for some years now and has recently reached a critical stage,” says Shiriyev.

Reduced inflows from Russia’s Volga River have been exacerbated by dam constructions and increased water use amid Western sanctions on Russia Azerbaijan has complained. This decline threatens maritime industries, including vital transport routes like the Trans-Caspian International Transport Route.

Ali Salajegheh, head of Iran’s Environment Department, attributed the decline in Caspian Sea levels in 2023 to Russia intentionally reducing the Volga inflow. While that has not been denied, some link the decline to natural variation, worsened by climate change.

“Lower river water levels would restrict inland water transport, which Russia relies on for trade—and increasingly for military purposes, another knock-on effect of the war in Ukraine,” says Shiriyev. “The Volga-Don Canal has allowed the Caspian Flotilla to travel to the Sea of Azov and Black Sea to reinforce the navy there, a crucial role since Turkey closed the Black Sea straits to military vessels from countries involved in the conflict, invoking the Montreux Convention.”

The falling water levels in the Caspian Sea threatens to disrupt trade in the entire region - not only for Russia but also routes from Central Asia to Europe through Azerbaijan. The Trans-Caspian International Transport Route, also known as the Middle Corridor, passes through Central Asia, the Caspian Sea, and the South Caucasus, and is crucial for trade between China and Europe.

“Officials in Kazakhstan and Azerbaijan, increasingly alarmed by the shrinking Caspian, say the issue is critical. Falling water levels impact every aspect of life, the maritime industry, and the region’s ecology, threatening the efficacy and economic potential of the Middle Corridor,” says Shiriyev.

The upcoming COP29 climate conference in Azerbaijan could provide a platform to address these environmental challenges, but geopolitical tensions and ongoing military activities complicate the prospect of effective multilateral solutions​​.