15,589 species threatened

Report card of species around the world finds those at risk increased by 3300 since 2000

Nov 17, 2004
Trevor Stokes(ts42@nyu.edu)

More than 15,000 species around the world are at risk of extinction, according to a report released today (November 17) by the International Union for Conservation of Nature and Natural Resources (IUCN). The organization, whose annual list of endangered species is commonly known as the "Red List," found that one in eight birds, almost half of turtles and tortoises, one in four mammals studied, and one in three amphibians is threatened.

"We are in the midst of the sixth great extinction wave on the planet Earth, caused by the intervention of humans," David Brackett, Species Survival Commission Chair of the study, told The Scientist. "Species should come and go on an evolutionary time scale, not on our time scale." Brackett said that "objective information is showing that declines are not limited to vulnerable species, but are happening across the entire taxonomic spectrum."

The report, released at the Third IUCN World Conservation Congress in Bangkok, is the work of 8000 volunteer conservationists in 179 countries and is considered the most comprehensive study of threatened species by international conservationists. It found that 15,589 species—3300 since the last such report in 2000, most likely because amphibians are now included—are at risk of extinction.

One major notable shift is that continental extinctions have become as common as extinctions on islands, typically thought of as more ecologically fragile. The report concluded that the current extinction rate is 100 to a 1000 times the "natural" evolutionary rate.

In a press release, Craig Hilton-Taylor, co-editor of the report, wrote: "Although 15,589 species are known to be threatened with extinction, this greatly underestimates the true number, as only a fraction of known species have been assessed. There is still much to be discovered about key species-rich habitats, such as tropical forests, marine and freshwater systems, or particular groups, such as invertebrates, plants and fungi, which make up the majority of biodiversity."

In both plants and animals, according to the report, species were more likely to be at risk if they had slow growth rates, small populations, and low reproductive rates—species such as sharks, the great apes, and cycads. But regardless of the characteristics of the species, humans are either directly or indirectly the main reason for most species' declines, according to a press release by the International Union. Threatened species are exposed to significant pressures that include over-exploitation, invasive species, pollution, and disease.

The hardest hit plant group is the cycads, ancient palm-like plants that survived from the dinosaur age, said the report, which lists half of cycad species as threatened. Cycads are one of the best studied species in the list. "We were able to get complete taxonomic data points on cycads." Brackett told The Scientist. Like various economically valued species, black market trade threatens cycads. Jody Haynes, a biologist at the Montgomery Botanical Center in Miami who specializes in cycads and palms, told The Scientist that he was informed about a patch of previously undescribed species in Honduras, but "when I got there, the cycads were all gone" because they had been stolen.

Conversely, the study highlights the knowledge gap in marine species. One reason is simply the lack of technology to properly survey such remote areas such as the oceans' depths, according to George Burgess, director of the Florida Program for Shark Research. "We've hardly scraped the surface, unlike the terrestrial world," Burgess told The Scientist. "Our ability to survey becomes a technological headache. The sad part is that many species are disappearing before we can find out the basics about them."

The next step, according to Sam Gon, director of science at the Nature Conservancy's Hawaii division, is to "look at what is necessary to preserve habitats to benefit the maximum [number] of endemic species." Hawaii has been particularly vulnerable to species loss: it contains a mere 0.2% percent of US land but holds a quarter of the endangered species in the United States. The Red List acts as "an official list that often brings status and funding to taxa that may not get attention at all," Gon told The Scientist. "You don't have to know everything to take action," he said.