from the WonkBlog at the Washington Post
by Brad Plumer
There have been five mass extinctions in Earth’s history. Now we’re facing a sixth.
There have been five mass extinction events in Earth’s history. In the worst one, 250 million years ago, 96 percent of marine species and 70 percent of land species died off. It took millions of years to recover.
Nowadays, many scientists are predicting that we’re on pace for a sixth mass extinction. The world’s species are already vanishing at an unnaturally rapid rate. And humans are altering the Earth’s landscape in far-reaching ways: We’ve hunted animals like the great auk to extinction. We’ve cleared away broad swaths of rain forest. We’ve transported species from their natural habitats to new continents. We’ve pumped billions of tons of carbon-dioxide into the atmosphere and oceans, transforming the climate.
Those changes are pushing more species to the brink. A 2007 report from the Intergovernmental Panel on Climate Change suggested that 20 to 30 percent of plant and animal species faced an increased risk of extinction this century if the planet keeps warming (though scientists are still debating these exact numbers, with some going far higher).
So what happens if the extinction rate speeds up? That’s one of the questions that New Yorker science writer Elizabeth Kolbert explores in her excellent new book, The Sixth Extinction, an in-depth look at the science of extinction and the ways we’re altering life on the planet. We spoke by phone this week about the topic.
Read the rest here.