The Causes of Dolphins Being Endangered

Habitat Loss and Pollution

• The plight of South Asia's Ganges River dolphin, also known as the susu or blind dolphin, provides an extreme example of environmental threats to the survival of some species. Despite identification with the Ganges, this dolphin lives in river systems spanning three countries, but according to the World Wildlife Fund, "this vast area has been altered by the construction of more than 50 dams and other irrigation-related projects." For freshwater dolphins, runoff and reduced river levels diminish available habitat, but dolphin species face other less obvious threats, including exposure to industrial toxins, which can accumulate at high levels in animals at the top of the food chain.

Entanglement in Fishing Nets

• Modern industrial fisheries take their toll as well. Dolphins used to die in the nets by the millions, snared as unwanted "bycatch" by boats pursuing tuna or other commercially valuable fish. Today, the IUCN says that problem has diminished, but that other driftnet and gillnet fisheries around the world continue to kill unsustainable numbers of dolphins. In the Mediterranean, for example, fishers reduced local populations of threatened species by more than 10 percent in a single year, despite a European Union ban on driftnets.

Hunting

• The IUCN cites commercial hunting, particularly by the Japanese whaling industry, as a continuing threat to some dolphin populations but smaller scale hunting also kills significant numbers. Indian fishers have targeted river species for their oil and meat. In Sri Lanka, fishers actually began going after dolphins deliberately once they discovered willing buyers for dolphins they once considered bycatch.

Case Study: China's Baiji

• The baiji, or Yangtze River dolphin, shows the looming threat of extinction, particularly for freshwater dolphins living in rapidly developing or highly populated areas. In 2003, the IUCN blamed fishing, boat collisions and dam construction for the decline of the species, and a six-week expedition in 2006 failed to locate a single survivor. After the expedition, one of the leaders, August Pfluger, told the BBC that "we have to accept the fact that the baiji is extinct. We lost the race." The IUCN's 2008 Red List classified the baiji as critically endangered and possibly extinct.