Our Broken Home
Hooke's observation wasn't exactly greeted with hugs and prizes. Theologians saw the idea as a challenge to the existence of God. Perfection was among the Creator's inherent qualities, and extinction implied that he had made...mistakes. Many mistakes. Beyond the church's objections stood a larger problem: for those less scientifically adept than Hooke -- which in 1667 was pretty much everyone -- the idea was almost inconceivable. It would take more than a century to prove Hooke's theory, and it wasn't until 1860 that the British paleontologist Richard Owen floated the idea that humans could play a part in the disappearance of other species. Our own ancestors, Owen believed, might have wiped out North America's ancient camels, cheetahs, and woolly mammoths some 10,000 years ago. How could that be? Humans were so puny, the wild so vast and ferocious.
Today we find ourselves vexed once again by religion and our own incomprehension, fumbling with the reality that humans are reconfiguring life on earth. The Christian right has convinced half the American public to reject one of the most basic tenets of modern science: evolution. Meanwhile, worries over a looming mass extinction -- what would be only the sixth in the earth's 4.6-billion-year history -- have matured from long-shot theory to probable event, driven by habitat loss and global warming. So here we are, stuck in the same old intellectual ditch, unable to wrap our minds around the catastrophe we're causing, let alone act to avoid it.
Just how big is that catastrophe? In Terra, the paleontologist Michael Novacek uses the disappearance of the dinosaurs as a benchmark. That die-off occurred 65 million years ago, between the Cretaceous and Tertiary periods, when an asteroid the size of Mt. Everest crashed into Mexico and triggered a pulse of thermal radiation that barbecued most life on the planet. How does our modern handiwork stack up? "If there is a phenomenon in the last 65 million years to match the trauma, destruction, and transformative power of the [Cretaceous/Tertiary] extinction event, we haven't found it yet," Novacek writes. "The only possible competitor, ironically, seems to be the trauma to the biota we are so peculiarly positioned to witness in our own time."
In other words: we have met the next killer asteroid, and it is us.
Novacek is the American Museum of Natural History's provost and senior vice president, and Terra is his bid to wave humanity off its destructive path. The book lays out the story of life on earth -- from the first single-celled organisms that arose some 3.5 billion years ago to today's carbon-spewing hominid -- with a singular purpose in mind. Novacek wants to make us care about what we're losing. "When an item is up for auction, its value is often elevated by knowledge about the source and the intricate history behind the piece," he writes.
Make no mistake -- Terra is great history. But it's also something more. Novacek brings recent findings to bear on centuries-old questions. Fresh fossil discoveries, new ice core data, and the blending of fields like geology, paleontology, and climatology are yielding a clearer picture of what existed in the past, how it came about, and why it died off. The implication, of course, is that if we want to understand how global warming will affect us and the world's other 1.75 million named species, we should study how analogous events played out in the past.
Take the rise of oxygen, for example. More than two billion years ago, photosynthesizing bacteria emerged from the primordial ooze (actually, the microbes probably were the primordial ooze) and began pumping oxygen into the atmosphere, which was then dominated by methane and carbon dioxide. If it were charted, that O2 spike might produce something like the hockey-stick graph of atmospheric CO2 made famous by Al Gore in An Inconvenient Truth. Novacek tracks what happened next: "Oxygen escaped to the atmosphere and accumulated to levels that spawned new species and new ways of life. Some of the species that exploited this oxygen-laden atmosphere included the lines leading to multi-cellular organisms -- plants, animals, and us." Where there are winners, though, there must be losers. "There were also casualties," Novacek writes. Many anaerobic organisms that thrived under previous conditions "were completely wiped out."
Or consider the conditions during the Carboniferous period, 354 million to 290 million years ago. The world's continents were then a single landmass, Pangea, concentrated near the equator. Things were hot and wet on Pangea. Equatorial positioning, combined with atmospheric carbon dioxide levels of 1,500 parts per million (nearly four times today's level), kept global temperatures high -- 72 degrees Fahrenheit on average, compared with 54 degrees today. Vegetation boomed. "As the plants died, their remains accumulated in wet peat, a global-scale compost heap, which through years of compaction from accumulating sediments above them turned to coal," Novacek writes. One of the ironies of our current situation is that by burning coal -- Carboniferous plants -- we're actively recreating the very atmospheric conditions that nurtured those plants in the first place.
Then there's the rise of man. Novacek notes that our evolution wasn't as simple as "a single-file procession from some stooping, knuckle-walking ape to Leonardo da Vinci." It was more like trial and error, and error, and error. Human history, he writes, was "a branching bush comprising numerous species that appeared and eventually died out, with only one surviving twig of Homo sapiens to represent its endurance."
But oh, the power of that twig. Even at our most primitive we've profoundly changed vast ecosystems -- just as they've changed us. Humans crossed the Bering land bridge from Asia into North America at least 14,000 years ago. That crossing happened because the last ice age locked up massive amounts of water in two-mile-thick glaciers, dropping sea level by 300 feet and exposing the bridge. Climate shaped evolution.
Climate continues to shape evolution, but today man pulls the levers. In the words of the Nobel-lauded Intergovernmental Panel on Climate Change, the scientific community has "very high confidence" that man-made greenhouse gases are spurring global warming: it's happening, and we're the cause. "In years past, many scientists regarded the [panel's] results as overextended," Novacek writes. "Now many are saying the opposite." Biodiversity loss is accelerating, supercharged by the double whammy of shrinking habitats and global warming.
As climate change transforms habitats, species adapted to those places must migrate to survive. But much of the wild is already so fragmented by human development that many animals have nowhere to go. Creatures that can't move, such as coral, are vanishing. A decade ago, estimates of vast species loss were called alarmist. "Many of us suspected that some of the doom and gloom might be overwrought," Novacek writes. Sadly, not so. Today, he says, "the prediction of a 30 to 50 percent loss of species by 2050 is realistic."
Novacek tells an alarming tale and he knows it. "Don't shoot the messenger," he pleads. Don't worry. Our policy with messengers is to ignore them. We're awash in evidence. The mystery is why we don't act.
Our own extinction event is happening almost overnight -- only the dinosaur-killing asteroid was faster -- but still it's too subtle and slow for many of us to perceive.
The battle to save the planet as we know it "has just begun," Novacek writes near the end of the book, but the preceding 354 pages argue that the fight will be won or lost in human time -- yours and mine -- and the consequences will play out in geologic time. We have but a brief moment of opportunity to wrap our minds around the profound changes we're effecting.