One-fifth of the world’s vertebrate species are threatened with extinction, but the situation would be worse if not for current global conservation efforts, a new study finds.
University of Michigan biologist Ronald Nussbaum is one of 174 researchers from 115 institutions and 38 countries who authored the study published in Science Express.
The study used data for 25,000 species from the International Union for Conservation of Nature’s Red List of Threatened Species to investigate the status of the world’s vertebrates (mammals, birds, amphibians, reptiles and fishes) and how this status has changed over time.
The results show that, on average, 50 species of mammal, bird and amphibian move closer to extinction each year due to the impacts of agricultural expansion, logging, over-exploitation, and invasive alien species.
“The ‘backbone’ of biodiversity is being eroded,” said the American ecologist and writer Edward O. Wilson of Harvard University. “One small step up the Red List is one giant leap forward towards extinction. This is just a small window on the global losses currently taking place.”
Southeast Asia has experienced the most dramatic recent losses, largely driven by the planting of export crops like oil palm, commercial hardwood timber operations, agricultural conversion to rice paddies, and unsustainable hunting. Parts of Central America, the tropical Andes of South America, and even Australia, have also all experienced marked losses, in particular due to the impact of the deadly chytrid fungus on amphibians.
While the study confirms previous reports of continued losses in biodiversity, it is the first to present clear evidence of the positive impact of conservation efforts around the globe.
Results show that the status of biodiversity would have declined by at least an additional 20 percent if conservation action had not been taken.
“Our results clearly demonstrate that conservation efforts are having a positive effect on maintaining global biodiversity,” said Nussbaum, a professor of ecology and evolutionary biology and a curator at the U-M Museum of Zoology. “This is encouraging, but we must not become complacent. Hopefully these results will persuade governments, research institutions, corporations, and individual donors to step up their conservation efforts.”
The study highlights 64 mammal, bird and amphibian species that have improved in status due to successful conservation action. This includes three species that were extinct in the wild and have since been re-introduced back to nature: the California Condor (Gymnogyps californianus) and the Black-footed Ferret (Mustela nigripes) in the United States and Przewalski’s Horse (Equus ferus) in Mongolia.
Conservation efforts have been particularly successful at combating invasive alien species on islands. The global population of Seychelles Magpie-robin (Copsychus sechellarum) increased from fewer than 15 birds in 1965 to 180 in 2006 through control of introduced predators such as Brown Rat (Rattus norvegicus) and captive-breeding and re-introduction programs. On Mauritius, six bird species have undergone recoveries in status, including the Mauritius Kestrel (Falco punctatus), whose population has increased from just four birds in 1974 to nearly 1,000.
In South America, protected areas and a combination of the Convention on International Trade in Endangered Species (CITES) and the Vicuña Convention helped spark the recovery of the Vicuña (Vicugna vicugna). Similarly, legislation enacted to ban commercial whaling has seen the Humpback Whale (Megaptera novaeangliae) move from Vulnerable to Least Concern. Unfortunately, few amphibians have yet shown signs of recovery, but international efforts are escalating, including a program to reintroduce the Kihansi Spray Toad (Nectophrynoides asperginis), back into the wild in Tanzania.
“In recent years field biologists have discovered more than a thousand new species of amphibians, mostly living in the tropics, and it is clear that many more amphibians remain to be discovered. But just as we’re beginning to understand the abundance of amphibians and their previously underestimated role in community ecology, we’re finding that they’re among the most threatened of the major vertebrate groups,” said Nussbaum, whose research focuses on amphibians and reptiles. “Special attention should be given to reduce the rate of extinction of amphibians and to restore the statuses of many threatened species to non-threatened categories.”
The authors caution that their study represents only a minimum estimate of the true impact of conservation, highlighting that some nine percent of threatened species have increasing populations. Their results show that conservation works, given resources and commitment.
They also show that global responses will need to be substantially scaled up, because the current level of conservation action is outweighed by the magnitude of threat.
The study found that among vertebrates the percentage of species threatened ranges from 13 percent of birds to 41 percent of amphibians. Although the study focused on vertebrates, it also reports on the levels of threat among several other groups assessed for the IUCN Red List, including14 percent of seagrasses, 32 percent of freshwater crayfish, and 33 percent of reef-building corals.
Recently, a UN-sponsored study called The Economics of Ecosystems and Biodiversity (TEEB) calculated the cost of losing nature at $2-5 trillion per year, predominantly in poorer parts of the world. A recent study found one-fifth of more than 5,000 freshwater species in Africa are threatened, putting the livelihoods of millions of people dependent on these vital resources at risk.