From the Bookshelf of Around the Year in 52 Books …

... there’s a dark synergy between fragmentation and global warming, just as there is between global warming and ocean acidification, and between global warming and invasive species, and between invasive species and fragmentation.  A species that needs to migrate to keep up with rising temperatures, but is trapped in a forest fragment - even a very large fragment - is a species that isn't likely to make it.  One of the defining features of the anthropocene is that the world is changing in wa

... there’s a dark synergy between fragmentation and global warming, just as there is between global warming and ocean acidification, and between global warming and invasive species, and between invasive species and fragmentation.  A species that needs to migrate to keep up with rising temperatures, but is trapped in a forest fragment - even a very large fragment - is a species that isn't likely to make it.  One of the defining features of the anthropocene is that the world is changing in ways that compel species to move, and another is that it's changing in ways that create barriers—roads, clear-cuts, cities—that prevent them from doing so.

Deep inside the Grotte, the walls are covered with hundreds of engravings. All the images are of animals, many of them now extinct: mammoths, aurochs, woolly rhinos. The most detailed of them possess an uncanny vitality: a wild horse seems to lift its head, a reindeer leans forward, apparently to drink.

It is often speculated that the humans who sketched on the walls of the Grotte des Combarelles thought their images had magical powers, and in a way they were right. The Neanderthals lived in Europe for more than a hundred thousand years and during that period they had no more impact on their surroundings than any other large vertebrate. There is every reason to believe that if humans had not arrived on the scene, the Neanderthals would be there still, along with the wild horses and the woolly rhinos. With the capacity to represent the world in signs and symbols comes the capacity to change it, which, as it happens, is also the capacity to destroy it. A tiny set of genetic variations divides us from the Neanderthals, but that has made all the difference.

Though many of the preceding chapters have been devoted to the extinction (or near¬ extinction) of individual organisms—the Panamanian golden frog, the great auk, the Sumatran rhino—my real subject has been the pattern they participate in. What I’ve been trying to do is trace an extinction event—call it the Holocene extinction, or the Anthropocene extinction, or, if you prefer the sound of it, the Sixth Extinction—and to place this event in the broader context of life’s history. That history is neither strictly uniformitarian nor catastrophist; rather, it is a hybrid of the two. What this history reveals, in its ups and its downs, is that life is extremely resilient but not infinitely so. There have been very long uneventful stretches and very, very occasionally “revolutions on the surface of the earth.”

To the extent that we can identify the causes of these revolutions, they’re highly varied: glaciation in the case of the end-Ordovician extinction, global warming and changes in ocean chemistry at the end of the Permian, an asteroid impact in the final seconds of the Cretaceous. The current extinction has its own novel cause: not an asteroid or a massive volcanic eruption but “one weedy species.” As Walter Alvarez put it to me, “We’re seeing right now that a mass extinction can be caused by human beings.”

The one feature these disparate events have in common is change and, to be more specific, rate of change. When the world changes faster than species can adapt, many fall out. This is the case whether the agent drops from the sky in a fiery streak or drives to work in a Honda. To argue that the current extinction event could be averted if people just cared more and were willing to make more sacrifices is not wrong, exactly; still, it misses the point. It doesn’t much matter whether people care or don’t care. What matters is that people change the world.

This capacity predates modernity, though, of course, modernity is its fullest expression. Indeed, this capacity is probably indistinguishable from the qualities that made us human to begin with: our restlessness, our creativity, our ability to cooperate to solve problems and complete complicated tasks. As soon as humans started using signs and symbols to represent the natural world, they pushed beyond the limits of that world. “In many ways human language is like the genetic code,” the British paleontologist Michael Benton has written. “Information is stored and transmitted, with modifications, down the generations. Communication holds societies together and allows humans to escape evolution.” Were people simply heedless or selfish or violent, there wouldn’t be an Institute for Conservation Research, and there wouldn’t be a need for one. If you want to think about why humans are so dangerous to other species, you can picture a poacher in Africa carrying an AK-47 or a logger in the Amazon gripping an ax, or, better still, you can picture yourself, holding a book on your lap.