Caspian Sea 2011
Hyrdro schemes are not currently a feature of the region, yet dams constructed 30 to 40 years ago are still having a regional impact. The construction of dams altered the water flow of all rivers in the area. The hydrological balance in deltas was changed, with consequent large-scale impacts on wetlands, water temperatures and on other factors. While the long-term impact of these changes is still not fully understood, there is no doubt that the whole eco- system of the Caspian Sea is affected. One of the clear impacts of the dam construction programme was the interruption of fish migration paths to spawning grounds and the destruction of those spawning areas. In total, about 80% of sturgeon spawning grounds were inundated as a result of dam-building. Sturgeons were cut off from their normal spawning ground in the Volga, Terek, Kura and Sefid-Rud rivers. Over the course of only two generations, this resulted in a dramatic reduction of sturgeon reproductive capacity and an overall decline in bioresources. Demographic factors such as population growth rarely have a direct impact on habitats and bio- diversity. However, demographics can have many indirect consequences, with specific impacts. An increase in population around the Caspian Sea has led to an increase in effluent runoff and more eutrophication. Other features of population growth are developments in coastal infrastructure including recreation centers and roads, and more agricultural activities with the conversion of wild areas to fields and pastures. An increase in night- time lighting can be a significant disturbance factor for birds, particularly in wetlands during nesting periods. Roads can interrupt the natural migration paths of gazelles and other mammals. Fishing and hunting are traditional human activ- ities in the region and it is now clear that fishing is exhausting many species resources. Stocks of lamprey, sturgeon, tulka, salmon, coregonids and several other species are depleted. The depletion of tulka stocks could have a large impact as it was the most abundant species in the Caspian Sea and functioned as a key part of the Caspian Sea food chain. Many predator species, especially seals, depend on tulka stocks.
Species invasions, both accidental and inten- tional, have been occurring in the Caspian Sea re- gion for hundreds of years. The majority of these species became integrated into the ecosystem without too much disturbance. However, the re- cent invasion of the comb jelly or Mnemiopsis liedye, disturbed the balance of the Caspian Sea ecosys- tem, resulting in a reduction of zooplankton di- versity. This has had a large impact on many fish species, particularly tulka.
Made with FlippingBook - Online catalogs