BARCELONA, SPAIN — At least one-quarter of the world's mammal species in the wild are threatened with extinction, according to an international survey released Monday that blames the loss of wildlife habitat as well as hunting and poaching for the steep declines.
The survey, assembled over five years by 1,700 researchers in 130 countries, is the most comprehensive yet to assess the status and future of mammals on every continent and in every ocean.
The baiji, or Chinese river dolphin, is teetering on the edge of extinction and may have already joined the list of species that have vanished from Earth. Others are not far behind, such as the vaquita, a small porpoise that has been drowning in fishing nets in the northern part of the Gulf of California; the North Atlantic right whale; and various monkeys and other primates hunted by poachers in Africa.
Scientists have determined that about 25% of the world's 5,487 species of mammals face extinction. The proportion of marine mammals in trouble appears to be higher, with an estimated one-third under serious threat of being wiped out. Many are killed when they are struck by ships or become entangled in fishing gear and drown.
About half the world's remaining species of apes, monkeys and other primates face threats from hunting or deforestation to make way for farming, said Russell A. Mittermeier, president of Conservation International.
"Chimp and gorilla meat fetches a higher price in many markets in Central African cities than beef or chicken because it's considered a luxury item," Mittermeier said. "We are losing many of these animals that otherwise could survive because they cling to relatively good habitat."
Scientists find these extinctions particularly worrisome because a diversity of species helps stabilize the planet. Each extinction can disrupt this balance and ripple through the food chain, making it more difficult for other species, including humans, to survive.
The bleak assessment was released in Barcelona at the World Conservation Congress, a meeting of 8,000 scientists, conservationists, business leaders and representatives from governmental environmental ministries. It was part of a larger update to the Red List of all threatened species, maintained by the International Union for the Conservation of Nature, which hosts this gathering every four years.
