o The Frog Blog: Biology Prize Entries 2011 - The Three Gorges Dam: Biological & Environmental Dangers

Wednesday, 9 March 2011

Biology Prize Entries 2011 - The Three Gorges Dam: Biological & Environmental Dangers

Every year it provides 18,200 MW electricity to the Chinese electricity supply system – the Three Gorges Dam. At first sight it seems to be a huge step by the Chinese government towards using the natural and renewable resource water as an energy supply. Hydroelectric power stations do not emit greenhouse gases and especially such a huge plant like the three gorges dam replaces the combustion of 50m tons of raw coal, prevents further increase in the amount of acid rain and thus diminishes the amount of soot particles in the air. But a deeper look at the construction and usage of the three gorges dam reveals numerous biological and environmental dangers.

About 300 species of fish used to inhabit the Yangtze River, but since the construction of the dam was initiated many are not able to travel upstream to spawn meaning the population of these species has decreased and many have become endangered. Also 47 other rare species like the Chinese Tiger, the Chinese Alligator and the Giant Panda suffered since either their habitats have been inundated or they suffered lack of nutrients.

A famous example for the negative impact of the three gorges dam on the ecosystem of the Yangtze River is the almost complete extinction of the Baiji Dolphin. The Yangtze River is the dolphins’ only natural habitat and before the dam was built there were already less than 100 of these endangered dolphins in the river. The reservoir of the dam covers a significant area of the dolphins’ habitat. For this reason the government had plans to create natural reserves and artificial spawning programs in order to prevent the extinction of the Baiji and other endangered species, but at that time it was already known that past attempts to resettle the Baiji had failed and today international scientists are quite sure that the extinction of this unique dolphin has become a reality.

Pollution is also a serious problem for the three gorges dam. About 13 cities, 1500 villages and large areas of forest have been destroyed to allow for the massive expanse of water. This huge areas of forest and agricultural fields are now flooded, which has already led to erosion and will have further consequences as the sediments build up in the reservoir. The problem that evolved is that the sediment from further upstream which contains valuable nutrients, which the farmers need in order to fertilise their fields, is blocked behind the dam. As a consequence the fertility of the farmers’ land downstream from the three gorges dam has already suffered at this stage, after only about 18 years since the dam was constructed.

Although the usage of hydroelectricity diminishes the pollution of the environment compared to other power plants, it nevertheless leads to a different kind of pollution. The extension of the riverbed upstream the dam has led to an increase in shipping of coal which pollutes the Yangtze River. The inundation of all the towns and villages that have been demolished has also set innumerable amounts of pollutants and landfill sites free to float in the river. Since the stream of the Yangtze River has been slowed down due to the three gorges dam the pollution has already settled down and diminished the quality of the water.

Another danger caused by the three gorges dam is the lower concentration of dissolved oxygen in the water of the Yangtze River downstream from the dam. In aquatic ecosystems this dissolved oxygen is necessary for most plants to survive since they need it for aerobic respiration. The dam has, as mentioned above, slowed down the movement of the water and thus made the natural process of diffusion of oxygen into the water more difficult. For most of these dangers there is unfortunately already a large range of scientific data that prove their seriousness.

Furthermore, another danger has developed due to the building of the dam. The increased erosion of fertile land, caused by higher water levels in the upper course of the river, has led to increased growth of algae in the water. Algae require large amounts of oxygen to grow, which in turn leads to the suffocation of fish and other animals in the immediate surrounding of the algae.

Mimi v Blomberg, Form VI

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