We Aren’t Destroying the Earth

Since humanity left Africa some tens of thousands of years ago, large land animals across the world have had a mysterious habit of dying out: giant kangaroo, woolly mammoth, glyptodont, to name a few. As Alfred Russel Wallace put it, we live in a world that lacks “all the hugest, and fiercest, and strangest” animals. It’s no wonder that invasive species are considered a big threat to wildlife, and none more so than the one species invasive on six out of seven continents: us.

Hence the “ecological despair” that the conservation biologist Chris Thomas identifies early in his provocative new book. “A mass extinction is in full swing, and prognoses for the future seem dire. For these reasons, we have gone so far as to describe ourselves as the scourge of the Earth, and as exceeding our planetary boundaries,” he writes. But Thomas is not interested in feeding this despair. Rather, he makes an argument considered apostasy by many: People’s impact on the planet has not been that catastrophic.

In other words, nature is more complicated, as the book explores in some detail. People spreading out across the globe and building international trade networks have reunited the continents in a kind of virtual supercontinent, mixing plant, animal, microbe and fungal species in a way unseen since Pangaea, more than 200 million years ago. Human alterations to the planet’s surface — like the conversion of most of the world’s grasslands into pasture and crops — have transformed the environment in which all other species thrive or die. As a result, some plants, animals, microbes and fungi win, and some lose.

The book is filled with such lovely anecdotes, many from Thomas’s own rich life of natural adventure, whether surveying sparrows in Italy or encountering pygmy elephants in Borneo. And though there are few flourishes in the writing, for a scientist, the prose is remarkably clear, if a bit repetitive at times.

The repetition serves a purpose though. Thomas is building a case, not telling a story. He argues that new species are arriving and evolving faster than old species are dying out globally. In the Atlantic region of Brazil, for example, one type of bird has been lost — Alagoas curassow R.I.P. — but two species have been gained: the cattle egret and the cattle-tyrant. There are more species of plants and animals in the tropics, therefore more species like it hot than cold, therefore maybe global warming will be good for more kinds of plants and animals. “Come back in a million years and we might” — by unleashing warm-weather biodiversity on the rest of the planet — “be looking at several million additional species whose existence can be attributed to the activities of humans,” Thomas writes.

Instead of a sixth extinction, it’s a sixth genesis.

The human impact on the course of evolution is clear — more types of species derived from sparrows, rats and eucalyptus. Thomas offers four rules for how we might cope with this brave new world he dubs Anthropocene Park: accept change, maintain flexibility (perhaps by swapping one species for another), acknowledge ourselves as a natural force and live within our means.

It’s the latter that seems like the biggest challenge currently, to this reader’s eyes. “Nature is fighting back” is a nice idea, but the reality is that Earth’s life revives only when we take the pressure off and let it. Actually fighting back would be a valid way to describe the present state of the environment only if there were some new hunter to prey on humans or perhaps a virus that lays our species low.

And Thomas relays only a little of the wonder of nature, like the evolution of a fly’s superpowered hearing to track down and find crickets. There is little recognition that such superpowers may be disappearing without our even knowing it, as the loser species fade away or the crickets learn to be silent. The mourned dead, like the great auk, the penguin of the north, only occasionally intrude.

Thomas relegates the ecosystem that covers some 70 percent of the Earth’s surface — the ocean — to a few perfunctory mentions. The resilience he otherwise locates on land might be harder to find there, thanks to human impacts like the reduction of the amount of oxygen in the water or its increasing acidity. When it comes to the ocean, we may not know enough even to know what we don’t know, or have already lost.

And even Thomas admits that the total number of species worldwide is down. As the ecologist Anthony Barnosky has calculated, we’ve already driven 1,000-plus species extinct, with another 20,000 or more in that dreadful queue.

“Who will remember even 100 years from now that the last individual of Rabbs’ fringe-limbed tree frog passed away on 26 September 2016,” Thomas writes. One can hope this book will help. We do remember Martha, the last passenger pigeon, or Cecil the lion and Lonesome George, the last Pinta Island tortoise. We need to preserve as many different species and habitats as possible on this “global Ark,” Thomas thinks. “We might presume that some presently rare species will be valuable to us in future — although we do not yet know which.” That certainly argues for keeping as many species around as possible, much as ecology’s forefather Aldo Leopold urged: “If the biota, in the course of aeons, has built something we like but do not understand, then who but a fool would discard seemingly useless parts? To keep every cog and wheel is the first precaution of intelligent tinkering.”

Instead, we are busily creating a homogeneous world, the diversity of plants and animals replaced by 22 billion chickens, 1.5 billion cattle, 1.2 billion sheep and a billion each for goats and pigs, a mix of species determined by the 7.5 billion Homo sapiens on the planet. If all those livestock were to disappear, we would eat through the remaining large animals in a month.

It is human concerns that determine everything here on Earth now. An animal that arrived in a particular location hundreds or thousands of years ago is fine with us, while a more recent immigrant, like garlic mustard, is cause for alarm and extensive campaigns to extirpate the interloper. Nostalgia is deadly, as people kill to preserve or restore some ill-remembered but more natural past, and we disdain new species as weeds. Anthropocene Park is truly a strange world in which people fly all over to see rare or declining animals and plants, emitting the greenhouse gases that may make those animals and plants extinct — an estimated 10 percent of land species may die off as a result of climate change, as Thomas notes. We are picking winners and saving losers and perhaps one day soon could make genetic changes to turn losers into winners. Maybe we want to get really crazy and set kangaroos loose everywhere in the world, Thomas suggests at one point.

That may sound a bit too much, but despair is all too easy these days. The vaquita, a tiny porpoise that lives in the Gulf of California, is on the verge of extinction, down to as few as 30 individuals as of this writing. Yet people have trained dolphins for military purposes that can now perhaps be used to herd their tiny cousin into refuges, where humans can work feverishly to save them, as we have done with the California condor or black-footed ferret. There has been a cultural transition away from killing animals for fun, food or fur and toward saving life. It’s not too late: The vast majority of species on the planet today can be saved. We still have a choice in how we end up changing the world.