As Species Vanish, We Discover More and More Creatures to Endanger

Since the last summary of the world’s mammals was published in 2005, tallying the roughly 5,400 mammalian species then known, Dr. Helgen said, an astounding 400 or so new species have been added to the list. “Most people don’t realize this,” he said, “but we are smack-dab in the middle of the age of discovery for mammals.”

Yet as he and other biologists are all too aware, we are also smack-dab in the middle of a great species smack down, an age of mass extinctions for which we humans are largely to blame. Estimates of annual species loss vary widely and are merely crude guesstimates anyway, but most researchers agree that, as a result of habitat destruction, climate volatility, pesticide runoff, ocean dumping, jet-setting invasive species and other “anthropogenic” effects on the environment, the extinction rate is many times above nature’s chronic winnowing. “Our best guess is that it’s hugely above baseline, a hundred times above baseline,” said John Robinson, an executive vice president at the Wildlife Conservation Society. “The problem is, we’ve only described an estimated 15 percent of all species on Earth, so most of what’s going extinct are things we didn’t even know existed.”

In sum, we have a provocatively twinned set of rising figures: on the one hand, the known knowns, that is, the number of new species that researchers are divulging by the day; and on the other, the unknown unknowns, the creatures that are fast disappearing without benefit of a Linnaean tag. To this second statistic must be added the “known no longers,” the named species that we’ve managed to directly or indirectly annihilate, like the Yangtze river dolphin, declared functionally extinct two years ago, or the dusky seaside sparrow, which tweeted its last in 1987.

Antithetical as they may seem, the two data sets are in many ways intertwined. One reason scientists are discovering more new species now than they were a couple of decades ago is that previously impenetrable places have been opened to varying degrees of development, allowing researchers to rush in and sample the abundance before it disappears. The gulp ’n’ go style of the global market can also deliver taxonomic novelty right to scientists’ door.