Marine life cemetery: The Caspian Sea ecosystem is collapsing under pressure from global warming and pollution

In late April, the carcasses of endangered seals were once again found on the shores of the Caspian Sea — marking the second mass die-off in just six months. Scientists have yet to agree on what’s driving the deaths: trawl fishing, pollution, disease, or the shallowing of the sea caused by global warming. Since 2020, the Caspian’s water level has been falling by roughly 30 centimeters a year, and the drop is not only disrupting oil transport and threatening navigation. Fish stocks are nearing collapse, and environmentalists are sounding the alarm over an unfolding ecological catastrophe. The Insider reports on what lies ahead for the Caspian, and how environmental advocates are pressuring the region’s governments to take meaningful action.

• 1.A breeze with a scent of decay
• 2.Why are the seals dying?
• 3.Warming waters and disappearing fish
• 4.Is the Caspian facing the fate of the Aral Sea?
• 5.Water retreat cuts supply lines: a blow to ports, cargo, and logistics

RU

A breeze with a scent of decay

The cool sea breeze in Karaman-6, a suburb of Makhachkala, brings no relief. Instead of fresh air, the beach reeks of death. The stench ebbs and flows with the gusts of wind. Walking here requires caution — you have to watch your step to avoid trampling bird carcasses. Some are nearly covered by sand; others have only recently washed ashore.

I stumble upon the first dead bird just minutes after descending a wooden staircase onto the beach. It is a large pelican, though only the beak hints at what species it once was. A few meters away lie smaller waterfowl, also lifeless. The beach reeks of rot and neglect. Judging by the number of decaying carcasses, local authorities are doing nothing to clean it up.

Dead pelican in the southern part of Karaman-6 beach in Makhachkala

But the main problem facing local residents is the dead seals. In December and January, dozens of endangered Caspian seals washed ashore, but their bodies were not removed until April, when concerned owners of nearby hotels and cafés raised the issue in the media ahead of the tourist season. The authorities reported that cleanup work had been carried out, but almost immediately new bodies began appearing on the beach. Locals say the waves bring them in daily. They are removed far less frequently. With no hope for help from city services, entrepreneurs involved in the local tourism industry have taken to disposing of the dead seals.

Every day, waves bring in the bodies of endangered Caspian seals

“There were two near our café, so we buried them ourselves — further away from the shoreline. They were small. The bigger ones were taken away by the city, yes,” says Akhmed, who owns an establishment on the beach. “It’s a pity, of course. We saw them here last December too.”

The beach at Karaman-6 is a quiet, peaceful spot located about 12 kilometers outside Makhachkala. “Clean sand and clear water. A gently sloping entrance into the sea makes it perfect for families with children,” read travel guide descriptions of the area. But today, as I walk the four kilometers of shoreline, I see tire tracks left behind by municipal services during seal carcass removal. Soon I come across two dead seals myself.

One large seal lies about 20 meters from the water, right near the staircase leading to the beach. It's partially covered in sand but still clearly visible. It’s an adult, around a meter and a half long. All around are dead birds, scraps of fishing net, tangled gear, and other debris. My companion Ahmed, the café owner, says the beach always looks like this after winter. Soon, he and other business owners will clean it up. Then he clarifies — he’s talking only about the area around the café, where he has already set out sun loungers.

Seal carcass and dead bird on the beach in Karaman-6 neighborhood

Another dead seal lies about 300 meters from the first one, right at the water’s edge. It’s a pup, likely born this past winter. Its coat is smooth and light gray, with a couple of wounds — peck marks from crows. Judging by its appearance, it died very recently and was washed ashore that very morning.

“If you walk along the beach, you’ll still see them lying there. It’s heartbreaking. It never used to be like this,” says a young woman walking with her elderly mother. “That smell is haunting me now.”

The Karaman-6 area boasts several resorts and guest houses offering various types of accommodation, along with hotels ranging from one to four stars. Their owners are hoping for a good tourist season. An ongoing ecological disaster in Anapa, the result of two fuel tankers running aground back in February, means Russian beach goers will have even fewer options than usual this summer. Karaman-6 and other coastal areas of Dagestan have become popular travel destinations in recent years, and federal TV is unlikely to warn vacationers about the surprise awaiting them there in the form of dead animals.

Why are the seals dying?

The seal deaths are not just a threat to the tourist season — they’re an ecological catastrophe. The Caspian seal is listed in the IUCN’s Red List of Threatened Species, and it is also on the protected lists of several countries in the region: Russia, Iran, Azerbaijan, Kazakhstan, and Turkmenistan.

Over the past century, the Caspian seal population has dropped by 90%, and the decline continues. In the past, the cause was unregulated hunting, but the reasons for today’s die-offs remain unclear. Locals have various theories.

“We’ve got patrol — what do you call them — steamships out there. The seals swim and hunt nearby. They get caught in the propellers, and the current washes them ashore,” suggests one fisherman on a Makhachkala beach. I’m reminded of the dead seal pup in Karaman-6 — its snout had been smashed.

Dead seal on the beach in the Karaman-6 area

“They say there’s some drilling going on in Kazakhstan,” suggests a Makhachkala resident walking the beach with her mother.

The first major mass die-off of seals was recorded in 2016, when around 300 carcasses washed ashore. At the time, the deaths were attributed to severe storms that had “accelerated the natural death” of mostly older animals. A similar event occurred in 2020, with hypoxia from natural gas emissions cited as the cause.

The Caspian Sea basin is indeed rich in natural gas seeps, from mud volcanoes to gryphons (points of fluid and gas release). If seals swim into such zones during migration, they may become trapped and suffocate, and researchers at the Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences found signs of asphyxiation in all the animals they examined. Scientists ruled out the possibility of shockwaves caused by geological surveys or military tests.

Then, in May 2021, 170 carcasses were found along the shore. Russia’s Ministry of Natural Resources concluded the animals had been accidentally caught in illegal fishing nets and dumped back into the sea. “Somebody’s fishing for sprat along their migration route, and then tries to cover their tracks,” said the then Minister of Natural Resources, Alexander Kozlov.

But the most tragic incident occurred in December 2022, when over 2,500 dead seals were counted on the beaches of Dagestan, with researchers at the local university naming influenza as the preliminary cause. At Maly Zhemchuzhny, there was also a mass bird die-off, and the virus responsible can also infect mammals.

In November 2024, around a thousand seals were discovered on the shores of Kazakhstan. “Such a number of washed-up seals is unprecedented,” said Mirgali Baimukanov, director of Kazakhstan’s Institute of Hydrobiology and Ecology. He noted that all the seals were young, well-fed, and many of the females were pregnant — signs pointing to sudden, unnatural deaths unrelated to age or starvation.

But not even autopsies and lab tests have provided a clear answer as to why the seals are dying. Weeks often pass between an animal’s death and the moment it washes ashore, and by then, samples taken from the carcass may no longer be reliable.

The seals’ very way of life complicates the picture. Caspian seals breed only on the ice of the Northern Caspian, then migrate seasonally to the south and back again. These are the periods when mortality spikes occur. Some experts believe that migration routes pass over areas with hydrocarbon seeps. The gases — methane, propane, butane mixed with hydrogen sulfide — are heavier than air and can hang close to the sea’s surface. When seals come up to breathe, they may inhale the toxic mix instead of oxygen.

Caspian seal pup Institute of Ecology and Evolution Problems,

Russian Academy of Sciences

Scientists report that the overall population of Caspian seals has dropped by up to 90% over the past few decades. In the early 1980s, there were around 450,000 seals, said Magomed-Rasul Magomedov, chief researcher at the Caspian Institute of Biological Resources at the Dagestan Scientific Center of the Russian Academy of Sciences. The sharp decline began in 2005, and by 2012, an aerial survey of the northern Caspian counted only 260,000 seals.

The decline only continued from there. “By 2019, the total seal population was estimated at 43,000 to 66,000,” Magomedov noted.

“In October last year, we were on an expedition and found no animals during the fall season. Only one seal was recorded on the Tyuleniy Islands,” said Mirgali Baimukanov, head of Kazakhstan’s Institute of Hydrobiology and Ecology. “Hundreds of thousands of seals used to live there in the 19th century. Tens of thousands in the early 20th. Now they’re gone. That’s the situation in the Northern Caspian. As for the Central Caspian, not a single seal was spotted on the Kendirli Islands.”

In October 2024, only one seal was recorded on the Tyuleniy Islands

Caspian seals face a major threat from wastewater pollution in the sea. According to the Russian state environmental watchdog Rosprirodnadzor, about 850 million cubic meters of wastewater are discharged into the Caspian from Dagestan every year. Of that, roughly 80 million cubic meters are released completely untreated, while the rest receives only partial treatment.

Local utilities are the main sources of pollution, as most coastal settlements in the republic lack sewage and wastewater treatment systems. Where such systems do exist, they are often critically outdated, and the situation is exacerbated by industrial facilities and agricultural complexes that dump waste without proper filtration. Over the past five years, activists and environmentalists have identified more than 100 illegal discharge points into the Caspian Sea in Dagestan alone.

Dead bird and remnants of fishing gear

In such an environment, not only seals, but also fish — the seal's primary food source — can become carriers of toxins. “Our sea is so polluted, both chemically and domestically, that a cumulative effect, pathological changes to the immune system, may have occurred,” says Magomed-Rasul Magomedov. “That means even background pollution or bacterial contamination can lead to mass die-offs.”

Some experts link the seal deaths to trawl fishing for sprat. The practice resumed in 2020, and although it is supposed to take place in deep waters, it is often carried out at middle depths. Seals, which rely on sprat as a staple food, end up in the nets. The large-scale harvesting of sprats alone may affect not just the seal population, but could also disrupt the entire ecological chain, as the fish is a food source for sturgeon, salmon, and other species.

Warming waters and disappearing fish

The central beach in Makhachkala is bustling. It’s one of the city’s most popular spots, and on warm days, it’s always full of visitors. This beach is much better maintained than the one in the Karaman-6 area. In the southern section, the sand underfoot is full of shells, while large rocks lie nearby. Almost every day, fishermen can be seen standing on them. Judging by the buckets filled with gobies, it’s been a lucky day.

“There are fish. We catch it, we eat it. We cook it the usual way — dry it, salt it, fry it in oil. We feed the cats too, and they’re not complaining!” says one of the fishermen, showing a fishing line with five gobies on it and a black-and-white cat keeping watch nearby.

Fishermen on a beach in Makhachkala

Everyone has heard about the dead seals, but according to locals, none have washed up on the central beach. The idea that the seals were poisoned doesn’t sound convincing to them. “What around here is clean anymore, really? Even the food we buy at the store — is that clean?” muses another hobby fisherman.

This conversation takes place towards the end of April, when a ban on recreational fishing running from April 15 to June 15 — during the spawning season, when fish are especially vulnerable — is already in effect. Throughout these months, large numbers of fish enter the Sulak, Samur, and Terek rivers, as well as the Kizlyar and Agrakhan bays, where they form spawning clusters.

While the North Caucasus territorial directorate of Russia’s Federal Fisheries Agency reports intensified raids against poachers, the Caspian Sea is facing a much deeper, systemic problem — a rapid decline in fish stocks. Despite tighter enforcement, the fishermen themselves admit that in practice, fishing continues as usual, and there’s little concern about inspections. Meanwhile, experts are sounding the alarm: the fish population in the Caspian is collapsing, and illegal fishing is only part of the problem.

According to Azerbaijan’s Ministry of Ecology and Natural Resources, fishing volumes in the Caspian Sea have significantly decreased over the past decade. The All-Russian Research Institute of Fisheries and Oceanography has issued a similar warning: over the past 35 years, the catch of Caspian roach has dropped sixtyfold.

Fishermen on the rocks in Makhachkala, with a tanker on the horizon

One of the driving factors is climate change. In 2021, record-high temperatures of 30 degrees Celsius were noted in the southern Caspian. Rising temperatures lead to decreased oxygen levels in the water and contribute to eutrophication — massive algal blooms that worsen living conditions for fish. These processes have already altered the species composition and pushed fish to migrate to the cooler regions of the mid-Caspian, said Elchin Mamedov, head of the department for fish stock assessment and catch forecasting at the Ministry of Ecology and Natural Resources’ Biodiversity Conservation Service.

The problem is multifaceted. Human economic activity, including marine pollution, also contributes to the degradation of biological resources. “If current fishing rates continue and climate change is ignored, the Caspian could lose a significant portion of its ecosystems in the coming years,” the All-Russian Research Institute of Fisheries and Oceanography warned. “A regional-level reassessment of how Caspian resources are used is essential.”

The Caspian Sea remains one of the world’s last major sturgeon spawning grounds. Over the past few decades, their population has already dropped by 90 percent, and falling water levels now threaten their key spawning sites. For the commercial fishing industry, this could mean losses in the tens of millions of dollars.

Maps show that even a 5–7 meter drop in sea level would leave sturgeon without their primary spawning grounds in the northern Caspian (spawning sites marked in purple on the right-hand map)

Losses for the fishing industries of countries bordering the Caspian are estimated in the billions of dollars annually. A five-meter drop in sea level could wipe out these fishing areas entirely.

Thus, even if anti-poaching efforts succeed, the situation cannot be salvaged without large-scale international adaptation measures. As a landlocked sea with a closed ecosystem, the Caspian is especially vulnerable, and its fish stocks are already rapidly shifting from a source of natural wealth to a scarce resource.

Is the Caspian facing the fate of the Aral Sea?

In March of this year, a blogger named Alexander decided to fly his drone over the coast of Aktau. He launched the Mavic above the staircase leading to the sea — exactly where he had flown it seven years earlier. But once the drone was airborne, he realized that he no longer recognized the coastline. The water had receded roughly 30 meters from its previous line — where the sea had once lapped the shore, only rocks remained.

“I came across an archived shot from 2018 and decided to return to the same spot, film a flyover, and document how far the sea had pulled back,” Alexander wrote on his blog. “I was shocked watching it live and comparing it with the old footage!”

The shrinking of the Caspian is another phenomenon that worries scientists. It could have devastating effects not only on the seal population, but on the entire ecosystem and the economies of both Caspian and non-Caspian countries.

Coastline of Aktau: left — 2018, right — 2025

Lada.kz / Instagram / alex_fpv_

True, the Caspian Sea’s water level fluctuated over the course of the 20th century. As an enclosed body of water fed by rivers, its level depends in part on natural factors like precipitation, snow cover, and weather. But historically, these changes were relatively minor. The Caspian lies below the global ocean level, and around 1900 it stood at -25.8 meters relative to sea level. By 1977, scientists recorded the lowest level since instrumental observations began in 1837: -29 meters. After a brief rise of 2.4 meters in 1995, the Caspian has been steadily receding, and by 2022, its level was again nearing that of 1977.

Climate models based on analyses of precipitation, evaporation, and river inflow suggest that the sea’s regression will continue through the end of the 21st century. Earlier projections estimated a drop of five meters by 2100, but the latest research indicates a decline of at least nine meters — and potentially as much as 21 meters — by the century’s end.

Photo by Alexander, shared with The Insider. The image shows how far the water has receded from the embankment of the city of Aktau in 2025

Scientists link the drop in water level to several factors, all related to human activity. One of the main causes is climate change, which leads to rising air and water temperatures. This accelerates evaporation from the sea surface, especially during hot summer months. The situation is further aggravated by a year-to-year decline in regional precipitation.

The second important factor is the reduction of river inflow feeding the Caspian. This is a direct consequence of human activity that began in full force in the 1930s. The sea receives water from about 130 rivers, with over 80% coming from the Volga, Ural, and Terek rivers in its northern part. The construction of reservoirs, irrigation systems, and dams, along with the use of river water for agricultural irrigation, has significantly reduced inflow. For example, due to intensive water use for agriculture in Kazakhstan and Turkmenistan, the catchment basins of rivers such as the Ural and Terek have greatly decreased their contribution to the sea.

If the shallowing continues, the endangered Caspian seals could disappear entirely

If the shallowing continues, the endangered Caspian seal could disappear altogether, since even a five-meter drop in water level would render most of the shallow areas crucial for seal reproduction inaccessible to them. A study conducted by scientists from the UK, Germany, Russia, Kazakhstan, Azerbaijan, and Turkmenistan lays out the most likely scenarios.

Four scenarios show the shrinking area of the Caspian Sea in the event of a sea level drop of 2.5 meters, 5 meters, 10 meters, and 15 meters. The forecast shows that with a drop of 10–15 meters, the Caspian seal would lose its breeding grounds (marked in purple) “Rapid decline of the Caspian Sea level threatens ecosystem integrity, biodiversity protection, and human infrastructure,”Nature, April 10, 2025

After a five-meter drop in sea level, around 77,000 square kilometers of the current water area (around 20% of the current surface of the Caspian Sea) will turn into land. The most affected areas will be the northern basin, Kara-Bogaz-Gol, and the Turkmenistan coastline. In the most extreme scenario, an 18-meter drop would cause up to 143,000 square kilometers of water to become land — a loss of 37% compared to the current area of the Caspian Sea.

The disappearance of ice in the northern Caspian could also negatively affect the seal population, even if the water does not recede. The animals use shallow areas covered with ice in winter for breeding. The presence of this ice is critical for the seals, as the pups must remain on the ice until their first molt — that is, until they can swim in the water. The absence of ice will deprive them of natural shelters from predators and wind, as pups usually hide between ice hummocks.

Water retreat cuts supply lines: a blow to ports, cargo, and logistics

Rising gas and oil production in coastal countries is also impacting water levels. The construction and operation of offshore platforms place added strain on the ecosystem, which over time may contribute to changing hydrological conditions. In Kazakhstan and Russia, for example, key oil fields lie in shallow waters. As water levels drop, these platforms risk becoming stranded far from the water, complicating hydrocarbon extraction and transport. This will inevitably drive up costs for infrastructure upgrades and the development of new logistics routes.

The falling Caspian Sea level is hampering efforts to increase oil shipments from Kazakhstan and is negatively affecting navigation safety. It already disrupts operations at the port of Aktau, a vital hub for transporting oil, grain, metals, and containers to Azerbaijan, Russia, Iran, and Turkmenistan. To ensure safe passage for vessels — including tankers — loads must now be reduced by 10%, according to Erbolat Tlepiev, head of the port’s department.

Port Aktau receives its 200th container train from China,

September 2024 rail-news.kz

For example, dry cargo ships with a capacity of 6,500 tons are loaded with only 5,500 tons, while tankers designed for 12,000 tons carry a maximum of 10,000 tons. This requires additional investment in infrastructure to adapt ports, deepen seabeds, and build new sea channels. In some cases, this will lead to increased transportation costs and, consequently, higher freight rates.

“If dredging is not completed by the end of 2025, the port will become unprofitable,” warned the administration of the Aktau port. The projected drop in water levels by 2.5–5 meters may also cause navigation problems in other major ports — Baku in Azerbaijan and Turkmenbashi in Turkmenistan.

When it comes to freight transport, the impact of shallowing will be especially noticeable in the northern and central sections of the Caspian Sea, where the Volga-Caspian canal is used for cargo transportation. Even a 5-meter drop in water level could make this canal impassable for international vessels, complicating cargo shipments between the Caspian Sea and the rest of the world. This will create additional logistical challenges and increase transportation costs, potentially causing long-term economic consequences for countries dependent on the Caspian region for shipping.

Ports without the sea. A forecast by scientists from the University of Bremen on the possible decline of the Caspian Sea level, published in the journal Nature, based on 15 climate models from the Coupled Model Intercomparison Project 6. Areas of drying are shown in red

The operability of Caspian ports, and thus the economic viability of the Caspian Sea, is critical not only for the countries of the region but also for the European Union. Amid the war in Ukraine, shipments along the Northern Corridor, which connects China with Europe by rail through Russia, have decreased significantly. Meanwhile, attacks by Yemeni Houthis have complicated maritime transport through the Indian Ocean, the Red Sea, the Suez Canal, and the Mediterranean Sea. This has made the Trans-Caspian International Transport Corridor the only direct and safe logistics route linking Asia and Europe. It passes through the Kazakh ports of Kuryk and Aktau, as well as Azerbaijan’s Baku, and a southern route — through the port of Turkmenbashi — also depends on the Caspian Sea.

The operation of these ports is also crucial in the context of the new joint EU-Central Asia investment initiative, The Global Gateway, which aims to enhance logistics between Europe, China, and countries in Central and Southeast Asia. This project was a central topic during the first visit to Uzbekistan by European Commission President Ursula von der Leyen and European Council President António Costa in February, a summit attended by the presidents of all Central Asian republics.

Advancing the project — particularly its logistics component — requires improving port navigability. However, environmental challenges and climate change are likely to impede the realization of The Global Gateway. If it is to overcome these hurdles, the European Union will need to actively participate in addressing the issue of the Caspian Sea’s declining water levels — not only for the sake of the seals, but for the economic health of countries located far away from the mammals’ shrinking habitat.