Have you ever heard about the South Asian river dolphin? This ancient species is scientifically called Platanista gangetica, and it's classified in two subspecies, the Ganges river dolphin (P. g. gangetica) and the Indus river dolphin (P. g. minor). It inhabits the fresh waters of Bangladesh, India, Nepal and Pakistan.
Sadly, this beautiful species is severely endangered in its two varieties, and we may be facing the extinction of the South Asian river dolphin. There are many reasons behind the decline in their population; stay with us at AnimalWised and discover why is the South Asian river dolphin endangered.
Where do South Asian river dolphins live?
Ganges river dolphins can be found in the counter-current pools below channel convergence. Annual monsoon-based floods cause massive variability in the access of these South Asian river dolphins to the larger part of their range. As a result, isolation in seasonal lakes and escapement into artificial river bodies have been known to occur.
The Ganges river dolphin once lived in the Ganges-Brahmaputra-Meghna and Karnaphuli- Sangu river systems of India, Nepal, and Bangladesh. Ganges river dolphins do not occur in waters of salinity higher than 10 ppt, though they have occasionally been recorded in saline waters of 23 ppt.
Indus river dolphins inhabit the deepest river channels, and they are less likely to be found in secondary channels. During the low water season, water levels drop and these river dolphins are concentrated in deep areas. This river dolphin subspecies can be found almost exclusively in Pakistan.
Here you can learn more about the different types of river dolphins and their habitats. In the picture you can see the Ganges River.
Why is the South Asian river dolphin's habitat endangered?
Water development projects in South Asia have affected the abundance, habitat and population structure of the river dolphin. Dams and barrages have not only fragmented the population, but also degraded habitats.
Canals are population sinks which dolphins enter, risking their safety. Inter-basin transfers through water diversion driven by agricultural and industrial demands is causing major problems for the South Asian river dolphin.
More than 50 dams have been constructed affecting the habitat of the Ganges river dolphins since 2000. Currently there are dams and similar projects in development in the Karnali river in Nepal and the Surma river in Cachar, India.
Besides fragmenting and dividing the South Asian river dolphin population, these man-made barriers also cause the formation of reservoirs with heavy sedimentation, leading to excessive salinity and destruction of habitats.
All in all, the main threats to the South Asian river dolphin's habitat include:
- Fragmentation of river dolphin population.
- Reduction and destruction of habitat due to dry-season flow.
- Escapement of river dolphins into canals.
- Cascading impact of prey organism migration and destruction of prey breeding habitats.
- Contaminants and toxins in the waters.
- Loss of habitat complexity due to channelization and sediment entrapment.
- Downstream effects of the ecology of the delta such as saline encroachment and loss of sediment.
- Embankments that reduce counter currents where river dolphins are found.
- Projects such as the Flood Action Plan by the World Bank which does not take loss of prey into account.
Why are the waters of the Ganges and the Indus rivers polluted?
The pollution in South Asian rivers has increased with industrialization and the spread of intensive agricultural techniques caused by water diversion. Toxins and pollutants can be found in the waters, and the rivers do not have the capacity to dilute them because of impoundments, diversion and water abstraction.
Arsenic and DDT as well as salts have contaminated the rivers inhabited by the South Asian river dolphins. Other toxins found in the tissues of Ganges river dolphins include butyltin and oragnochlorine, which increased with industrialization and agriculture.
Industrial pollution harms the habitat of the South Asian river dolphin, especially in counter-current pools of confluence and sharp meanders close to urban areas. Therefore, industrial, agriculture and human-induced pollution has led to this sharp habitat degradation.
It is estimated that 9,000 tons of pesticides and 6 million tons of fertilizers are in the vicinity of the Ganges River each year, and the effects of these products can be noticed in the bodies of South Asian river dolphins, which show toxic chemicals.
Besides industrial waste, municipal sewage and effluents as well as overexploitation of prey are some of the reasons why the South Asian river dolphin is endangered.
Why are South Asian river dolphins hunted by poachers?
One of the reasons why South Asian river dolphins are endangered is direct action by humans. These dolphins are hunted by people in the Brahmaputra River for meat and by fishermen in the Ganges River for oil. Dolphin oil is a valuable fish bait, so fishermen have a great incentive to kill these gentle creatures.
The preferred habitat of the Ganges river dolphins is in the same locations as fishing grounds in the middle Ganges. Fishermen even set their nets strategically to capture the dolphins; Gangetic dolphins face mortality by fishing gear, such as gillnets. A well-funded and corrupt fishery wildlife management system further aids the problem.
River dolphins trapped in dams are the target of poachers, even more so during dry months of summer. Below the dam, the dolphins are threatened by pollution as much as by fishermen and vessel traffic. All in all, dams disturb the migration and breeding cycles of the South Asian river dolphins as much as their natural habitat.
How do water management projects endanger river dolphins?
Habitat degradation on account of dredging and removal of stones and debris is dangerous to the river dolphins, as these activities harm the integrity of the river ecosystem.
Their natural habitat is also under threat by water abstraction from tube wells and surface pumps. Reduced water supply and dry-season flows will have a catastrophic effect on the river's population, not only on the South Asian river dolphins.
Why is the Ganges river dolphin endangered?
Living in one of the most densely populated regions of the world, the Ganges river dolphin has been particularly threatened by damming rivers for irrigation and electricity generation. Consider that more than 20 barrages and 18 high dams have been constructed in the GBM region since the 1950s and new projects are on the anvil and you will understand the magnitude of the threat.
River dolphin strandings are on the rise due to habitat loss. Used as catfish bait, Ganges river dolphins are also subject to accidental entanglement in fishing nets.
Why is the Indus river dolphin endangered?
Indus river dolphins are also under threat due to the construction of some 25 dams and barrages; this has reduced the available habitat and led to population fragmentation. Irrigation canals are also an obstacle, because the Indus river dolphins swim into them. Migration affects reproduction and leads to higher mortality rates.
Escalating demand for water due to Pakistan being a desert nation is also a reason why natural habitats are becoming dry, threatening the Indus river dolphin. Reduced flows and high pollution loads from industrialized Punjab cities is another the reason for the destruction of this subspecies. It is also harmed by agricultural effluents which are used on crops in riverbanks.
Why is the South Asian river dolphin endangered, then? As you can see, there are many reasons, but they mostly have to do with the negative impact of human populations and their demand for resources.
Stay with us to learn all about endangered wildlife and how to protect it, including:
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- Endangered animals in the Great Barrier Reef
- Why are giraffes a vulnerable species?
- Why is the house sparrow population decreasing?
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