The most exhaustive study every undertaken on the future of mammals, the broad family of animals to which humans belong, has found that more than a third of all marine species and a quarter of those living on land are at risk of extinction.
The researchers – who are publishing their results in the current issue of Science – found that the larger the size of mammal, the more likely it was to be facing a perilous future.
The finding suggests that without major conservation measures, big iconic animals such as polar bears, great apes and hippos will soon be rare or non-existent, at least in the wild. Mammal species would then be dominated by small creatures belonging to such groups as the rodent and bat families or somewhat larger ones, such as raccoons and coyotes, that are able to adapt to human interference in the environment.
Even many of the species not at risk of outright extinction are in trouble, according to the study, which found a worrisome trend: Half of all types of mammals are experiencing population declines.
“It's a critical time in the conservation of mammals,” observed Andrew Derocher, a leading Canadian polar-bear expert and biologist at the University of Alberta, who helped conduct the research. “We really are on a tipping point in terms of species loss.”
The study, to which more than 1,700 of the world's leading experts contributed, blamed the massive impact humans are having on the global environment.
Habitat loss and hunting “are by far the main threats” for land mammals, the study says, although marine species are also being affected by chemical pollutants, climate change and mortality through ship collisions and entanglement in fishing nets.
“The drivers behind this are very clear. … These are all pressures caused by human activities and a growing human population,” said Cormack Gates, University of Calgary professor of environmental science and a co-author.
The research is considered the most comprehensive ever undertaken of the known 5,487 species in the mammals group. Mammals, which range in size from bats and mice to whales, are the branch of life characterized by being warm-blooded, bearing live young and having females that feed their newborns milk.
The biologists who did the assessment, led by the International Union for Conservation of Nature, didn't have enough information to determine the outlook for all species.
But for those for which adequate data were available, 1,139 faced the possibility of extinction.
Among these, the plight of 188 was so dire that researchers deemed them “critically endangered.” with a high probability that they won't survive much longer.
These creatures include the baiji, a rare freshwater dolphin from China's Yangtze River that is considered on the edge of extinction or possibly extinct.
If the Chinese dolphin has already died out, as many biologists fear, it would be the first modern-era loss of a marine mammal species since the 1700s, when hunting wiped out the Steller's sea cow, a huge sea-like creature that once lived on the Asian side of the Bering Sea.
Among land mammals, the most threatened species are concentrated in South and Southeast Asia. The study said “a staggering” 79 per cent of primates in this region are threatened with extinction. It singled out the Western Ghats in India, a region with a rich ecosystem that includes wild elephants and mongooses, as a high-risk zone. In the Americas, the tropical Andes in South America is considered another likely extinction hot spot.
Although the study highlighted the threat to mammals, Prof. Derocher said there have been some success stories where concerted conservation efforts brought species back from the brink. One such case is the swift fox, a tawny-coloured canine the size of a house cat, which was formally extinct in Canada but has been successfully reintroduced into Alberta from U.S. stock and has since spread to Saskatchewan.
But many species won't be so lucky, if the projections hold.
Future human societies, Prof. Derocher said, will “marvel that we were so short-sighted, that we didn't do something in time.”
