Three Asian species of dolphins may go extinct by 2020 if governments fail to cut pollution and destruction of the species’ habitats, according to scientists at the Ocean Park Conservation Foundation in Hong Kong. The first dolphin species to go will likely be China’s baiji dolphin; there are only about 30 left in the Yangtze River. Pakistan’s river dolphin, the bhulan, and the irrawaddy dolphin of southeast Asia are also in trouble. Insecticides and PCBs pollute Asia’s river systems, and tests conducted on dolphins in the region have found high levels of mercury and heavy metals in their bodies. The animals are also threatened by dams, irrigation, development along coastal areas, and hunters who try to catch dolphins for Chinese aquariums.