Earth's plants and animals are vanishing at a rate that's 10 to 100 times faster than previous estimates suggested, according to a new analysis of changes to the planet's biodiversity.
Yet even the new estimate of the pace of extinctions is likely to be too low, according to the analysis, which is set to appear in Friday's issue of the journal Science. By its nature, the new estimate doesn't include millions of species that biologists have yet to describe or discover.
New discoveries, researchers note, often involve species highly specialized to a relatively small habitat – a habitat that human encroachment is fragmenting or altering in dramatic ways. This suggests that as new species are discovered, they are likely to be facing serious threats and may be endangered.
But amid the mounting evidence that Earth is undergoing its sixth mass extinction, there is reason for hope, notes Stuart Pimm, a conservation ecologist at Duke University in Durham, N.C., and the lead author of the review.
"This is not all gloom and doom," he says. Within the past five years, sophisticated, public databases of global marine and land-based plants and animals have emerged, built in part by citizen scientists who use smart phones to snap images of a plant or animal, pinpointing the time and location of the picture.
One clearinghouse for smart phone data, iNaturalist.org, has delivered more than 500,000 quality-checked and approved observations worldwide into the Global Biodiversity Information Facility, a database funded by governments around the world.
The confluence of powerful data-gathering and analysis tools, and the influx of new information from backyards, woods, fields, and even a US military latrine in Iraq, "puts us in a much better position to manage biodiversity than we were even five years ago," Dr. Pimm says.
"We can be more focused in how we act," which in turn can help accelerate conservation efforts, he says.
As an example of the power of these data, he cites an area along Brazil's coast that has more threatened species than anywhere else in the Western Hemisphere. One key reason: The habitats are extensively fragmented, a condition that can play a key role in triggering extinctions. Based on information from global databases, a conservation group in Brazil has been able to pinpoint the fragments and buy land in between them to try to rebuild the habitats and ensure that species can move among them.
The analysis in Science was not designed to be the definitive word on changing biodiversity and extinctions. Instead, the aim was to provide an updated estimate of extinction rates as well as map species' distribution and the protected areas designed to nurture them. The study is expected to help guide a broader global biodiversity analysis by the Intergovernmental Platform on Biodiversity and Ecosystem Services, an international science advisory panel set up to track progress toward meeting conservation goals for 2020 set by the Convention on Biological Diversity. The convention was one outcome of the first United Nations-sponsored Earth Summit, held in Rio de Janeiro in 1992.
Coming up with estimates for known species is tough, note Pimm and eight colleagues from institutions in the United States, Brazil, Britain, and Switzerland. Some 300,000 plant species have names that scientists accept, but catalogs contain species with multiple names, with some 264,000 plants that haven't received widely accepted names yet.
Sifting through the data, the team estimated that some 400,000 plants are known, with another 50,000 remaining to be discovered. As for animals, 1.9 million species have been described, with anywhere from 5 million to 11 million species yet to be described.
Several lines of evidence suggest that one could have expected to see, averaged over the globe, 1 in 10 million species vanish in a given year without a human influence on the environment. Today the rate is 1,000 times to 10,000 times that background rate and rising as human populations continue to encroach on other species' habitats.
Global warming is altering habitats and by some estimates is expected to drive from 4 to 7 percent of marine species extinct by 2050, while 10 to 14 percent of land species would follow suit. Still, the dominant driver of extinctions remains outright habitat destruction, the team observes. Until the models projecting future declines can be compared against existing extinctions and include a wider variety of contributors, from disease to invasive species, estimates of future losses will carry large uncertainties, the researchers suggest.
Crowd-sourcing efforts to gather data on species will be a big help in filling data gaps and assessing the effectiveness of protected areas, Pimm says, adding that gathering the data doesn't necessarily mean tromping over the same ground day after day snapping pictures.
The serendipitous observation can be enlightening as well.
Pimm recalls a trip to Brazil during which he came across a frog he didn't recognize and snapped its picture, recording a species that no one else seemed to know about, either.
Some expeditions are less exotic.
In May 2011, during iNaturalist.org's Global Amphibian BioBlitz, a US soldier serving at Joint Base Balad in Iraq was making a routine visit to the latrine when he found a yellow tree frog inside. He released it outside, snapped a photo, then uploaded it to iNaturalist.org.
It turned out that the species hadn't been seen before within several hundred miles of the base, Pimm says, adding, "It's indicative of the wonderfully idiosyncratic way in which observations take place."