The Earth has been stripped of up to 90% of its species five times before in the past 450 million years. Now it's happening again—and this time there's no rogue asteroid responsible.
One of the first great rules of terrestrial biology is that no species is forever.
The Earth has gone through five major extinction events before—from the Ordovician-Silurian, about 350 million years ago, to the Cretaceous-Paleogene, 65 million years back. The likely causes included volcanism, gamma ray bursts, and, in the case of the Cretaceous-Paleogene wipeout, an asteroid strike—the one that killed the dinosaurs. But the result of all of the extinctions was the same: death, a lot of it, for 70% to 90% of all species, depending on the event.
As increasingly accepted theories have argued—and as the Science papers show—we are now in the midst of the sixth great extinction, the unsettlingly-named Anthropocene, or the age of the humans.
The numbers are sobering: Over all, there has been a human-driven decline in the populations of all species by 25% over the past 500 years, but not all groups have suffered equally. Up to a third of all species of vertebrates are now considered threatened, as are 45% of most species of invertebrates. Among the vertebrates, amphibians are getting clobbered, with 41% of species in trouble, compared to just 17% of birds—at least so far. The various orders of insects suffer differently too: 35% of Lepidopteran species are in decline (goodbye butterflies), which sounds bad enough, but it’s nothing compared to the similar struggles of nearly 100% of Orthoptera species (crickets, grasshoppers and katydids, look your last).
Facebook
Twitter