Caspian Sea ecosystem
The Caspian Sea, the world's largest enclosed body of water, spans approximately 143,244 square miles (371,000 square kilometers) and is bordered by five countries: Kazakhstan, Russia, Azerbaijan, Turkmenistan, and Iran. This unique ecosystem, a remnant of the ancient Thetis Ocean, showcases diverse aquatic life, with around 80 percent of its species being endemic. The Caspian Sea's waters vary in salinity from fresh in the northern regions to brackish in others, and it is home to numerous fish species, including various types of sturgeon, which are vital both ecologically and commercially. However, the region faces significant environmental challenges, including pollution from industrial activities, overfishing, and climate change, which threatens the delicate balance of its ecosystem. Additionally, the geopolitical importance of the Caspian Sea is amplified by its vast oil and gas reserves, leading to complex resource management issues among the bordering nations. The health of the Caspian Sea's ecosystem is critical not only for local biodiversity but also for the economies reliant on its natural resources. As climate patterns shift, the future of the Caspian Sea remains uncertain, necessitating concerted conservation efforts and sustainable management practices.
Caspian Sea ecosystem
- Category: Inland Aquatic Biomes.
- Geographic Location: Asia.
- Summary: Due to large oil reservoirs in the Caspian Sea, the world's largest enclosed body of water is facing geopolitical and environmental issues from the five countries that border its shores.
The Caspian Sea is the largest enclosed body of water on Earth with a surface area of 143,244 square miles (371,000 square kilometers), a volume of 18,761 cubic miles (78,200 cubic kilometers), composing at least 40 percent of the total inland waters of the world. The land-locked body of water, considered a sea by some and a lake by others, has no outflows. Kazakhstan is located on the sea's north and northeast coasts, Russia is to the northwest, Azerbaijan is on the west, Turkmenistan to the east, and Iran is on the southern shore. Oil and gas reserves and pipelines, along with the ancient and modern trade routes, define the region's geopolitical and economic climate.
The Caspian Sea is a relic of the ancient Thetis Ocean, which served as a link between the Atlantic and Pacific Oceans. Due to tectonic uplift and a fall in the worldwide sea level, the Caspian became landlocked some 5.5 million years ago. Its water is a mix of fresh and saline, depending on the location. The body of water has freshwater in its northern portions and is brackish elsewhere, with salinity of about one-third that of the global oceanic average.
More than 130 rivers empty into the Caspian. The Volga River drains 20 percent of Europe's land area and enters from the northwest, its delta channels providing three-fourths of the Caspian's freshwater inflow. Among others, the Ural and Kura Rivers empty into the sea from the north and the west, respectively.
To the west and south, the Caspian Sea is framed by the Caucasus and Alborz Mountains; in the latter range is Mount Damavand, at 18,600 feet (5,670 meters) the tallest peak in Eurasia west of the Hindu Kush range in central Asia. By contrast, the lands to the north and east of the sea tend to be flat steppe. Indeed, the semi-arid desert of the Caspian Depression is as much as 430 feet (130 meters) below sea level.
Depths in the Caspian Sea vary dramatically, too. The northern part is a shallow shelf with an average depth of just 16 to 20 feet (2 to 6 meters). Most of the Caspian islands lie in this region, with a total area of approximately 772 square miles (2,000 square kilometers). The islands are small and mostly without human settlements. The island of Ogurja Ada, at 23 miles (37 kilometers) long, is the largest. The middle part of the Caspian has an average depth of 623 feet (190 meters), and the deepest parts of the southern basin plunge more than 3,281 feet (1,000 meters).
The northern portion freezes in the winter; if the weather turns very cold, the water's surface freezes in the Caspian's southern area. Cold continental desert climate rules the northern region, except for a more temperate and moist zone around the Volga delta, while a warm temperate climate embraces the southernmost extent.
Biota
Due to its enclosed nature, the aquatic plants and animals in the Caspian reach a very high level of endemism (species found exclusively here), as much as 80 percent. Despite the challenges of its variable salinity conditions, the Caspian Sea is home to 87 species of microphytes and many species of green algae.
Wetlands at the inflow points of its rivers give the Caspian various grassland and forest habitats as well. The Volga delta harbors such characteristic wetlands vegetation as waterwheel plant (Aldrovanda vesiculosa) and Caspian lotus (Nelumbo caspica). In the floodplain of the Samur River, which enters the Caspian from the Caucasus, a liana forest is found.
The most emblematic aquatic species here are the various types of sturgeon; the Caspian Sea was home to more than three-quarters of all sturgeon in the world as recently as 1980. Among the key species are Russian sturgeon (Acipenser gueldenstaedtii), Persian sturgeon (A. persicus), star sturgeon (A. stellatus), and beluga or European sturgeon (Huso huso). Being anadromous, these fish use the major rivers as spawning grounds—a fact that has acted to deplete their populations here in part due to dam construction.
Other Caspian fish, important both commercially and to the ecosystem, include the kutum or Caspian whitefish, salmon, marine shad, Caspian roach (Rutilus caspicus), and white-eyed bream (Abramis sapa).
Tyuleniy Archipelago in the northeastern Caspian Sea is an important area for waterbirds such as swans, coots, and egrets. Caspian gull (Larus cachinnans) and Caspian tern (Hydroprogne caspia) are among the endemic avian species here.
Among mammals unique to this biome, the Caspian seal (Pusa caspica) is one of just two inland seals in the world, the other being endemic to Lake Baikal in Siberia. The Caspian seal seems to be comfortable in all areas of the Caspian Sea, as well as some river stretches. It also varies in its birthing regimen, perhaps preferring ice floes in the northern waters but also seen giving birth on sandbars further south. These seals feed on crustaceans as well as fish of the Clupeonella genus.
Environmental Concerns
Since the Caspian Sea has a closed basin, it has no natural outflow except evaporation. Therefore, its sea level has been inconsistent over the centuries. Scientists have noted that the sea level changes in the Caspian are linked to atmospheric conditions in the North Atlantic. The cycles of the North Atlantic Oscillation, a climatic phenomenon of atmospheric pressure at sea level, causes variations in the interior depressions of Eurasia, resulting in the fluctuating rainfalls in the Volga River valley. This climate regime eventually affects the level of the Caspian Sea and increases its significance in global climate change studies.
The rivers of the Caspian carry large quantities of industrial pollutants from their catchment basins, endangering the biological environment of the Caspian. Overfishing is another threat, particularly to the sturgeon, whose eggs are processed into quite valuable caviar. Caviar harvesting targets reproductive females of this slow-to-mature fish family, putting its sustainability even more at risk. Conservationists have suggested bans on sturgeon fishing in the Caspian until the population fully recovers.
Because of the construction of water channels and canals like the Volga-Don during the twentieth century, many species were introduced to the Caspian from the Black and Mediterranean Seas. Some of these could not survive properly, while others were hostile to some native species. Mineral extraction, underwater oil drilling, and gas pipelines, coupled with transport activities, are additional environmental threats to the Caspian's ecosystem.
Geopolitical Issues
Various islands near the coast of the Caspian Sea have strong geostrategic significance. Nargin, the largest island in Baku Bay, served as a base for the former Soviet Union. The region also is important because of its oil resources, production of which dates as far back as the 10th century. Some of the world's first offshore wells and machine-drilled wells were made in Bibi-Heybat Bay in Baku, present-day Azerbaijan. The greater Caspian-Caucasus area once provided more than two-thirds of the Soviet Union's entire oil production. The fields are still producing; in 2006, Azerbaijan began transporting oil to Turkey through the Baku-Tbilisi-Ceyhan pipeline.
The fate of fossil-fuel projects here is subject to agreements among the five littoral states of the Caspian about the use of the sea for oil excavation, transportation—and the impacts on commercial fishing. Various issues concerning how to divide the resources of the Caspian Sea remain to be settled between Russia, Iran, Azerbaijan, Kazakhstan, and Turkmenistan. Not only overland pipelines but also the use of riverways and canals hold weight in negotiations. The Volga River, for instance, connects the Caspian Sea through the canals with the Black Sea, Baltic Sea, Northern Dvina, and White Sea. It is the only way at present that the landlocked states of Azerbaijan, Kazakhstan, and Turkmenistan can gain access to international waters.
Climate Change
The water level of the Caspian Sea is decreasing. Researchers predict that by the end of the century, it will lose 9 to 18 meters (about 30 to 59 feet) of depth. Losing so much water will decrease its size by 25 percent, uncovering 93,000 square kilometers (35,908 square miles) of land. Climate change is to blame. The level of the Caspian Sea depends on how much water flows into it from rivers, in particular the Volga river. The water level also depends on rainfall and evaporation. The increase in temperature will significantly increase evaporation, making the water level of rivers lower, as well as the water level of the Caspian Sea.
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