Over the past decade, Elizabeth Kolbert has established herself as one of our very best science writers. She has developed a distinctive and eloquent voice of conscience on issues arising from the extraordinary assault on the ecosphere, and those who have enjoyed her previous works like “Field Notes From a Catastrophe” will not be disappointed by her powerful new book, “The Sixth Extinction: An Unnatural History.”
Kolbert, a staff writer at The New Yorker, reports from the front lines of the violent collision between civilization and our planet’s ecosystem: the Andes, the Amazon rain forest, the Great Barrier Reef — and her backyard. In lucid prose, she examines the role of man-made climate change in causing what biologists call the sixth mass extinction — the current spasm of plant and animal loss that threatens to eliminate 20 to 50 percent of all living species on earth within this century.
Extinction is a relatively new idea in the scientific community. Well into the 18th century, people found it impossible to accept the idea that species had once lived on earth but had been subsequently lost. Scientists simply could not envision a planetary force powerful enough to wipe out forms of life that were common in prior ages.
In the same way, and for many of the same reasons, many today find it inconceivable that we could possibly be responsible for destroying the integrity of our planet’s ecology. There are psychological barriers to even imagining that what we love so much could be lost — could be destroyed forever. As a result, many of us refuse to contemplate it. Like an audience entertained by a magician, we allow ourselves to be deceived by those with a stake in persuading us to ignore reality.
For example, we continue to use the world’s atmosphere as an open sewer for the daily dumping of more than 90 million tons of gaseous waste. If trends continue, the global temperature will keep rising, triggering “world-altering events,” Kolbert writes. According to a conservative and unchallenged calculation by the climatologist James Hansen, the man-made pollution already in the atmosphere traps as much extra heat energy every 24 hours as would be released by the explosion of 400,000 Hiroshima-class nuclear bombs. The resulting rapid warming of both the atmosphere and the ocean, which Kolbert notes has absorbed about one-third of the carbon dioxide we have produced, is wreaking havoc on earth’s delicately balanced ecosystems. It threatens both the web of living species with which we share the planet and the future viability of civilization. “By disrupting these systems,” Kolbert writes, “we’re putting our own survival in danger.”
The earth’s water cycle is being dangerously disturbed, as warmer oceans evaporate more water vapor into the air. Warmer air holds more moisture (there has been an astonishing 4 percent increase in global humidity in just the last 30 years) and funnels it toward landmasses, where it is released in much larger downpours, causing larger and more frequent floods and mudslides.
The extra heat is also absorbed in the top layer of the seas, which makes ocean-based storms more destructive. Just before Hurricane Sandy, the area of the Atlantic immediately windward from New York City and New Jersey was up to nine degrees warmer than normal. And just before Typhoon Haiyan hit the Philippines, the area of the Pacific from which it drew its energy was about 5.4 degrees above average.
Our oceans, a crucial food source for billions, have become not only warmer but also more acidic than they have been in millions of years. They struggle to absorb excess heat and carbon pollution — which is why, as Kolbert points out, coral reefs might be the first entire ecosystem to go extinct in the modern era.
The same extra heat pulls moisture from soil in drought-prone regions, causing deeper and longer-lasting droughts. The drying of trees and other vegetation leads also to an increase in the frequency and average size of fires.
Food crops are threatened not only by more pests and the disruption of long-predictable rainy season-dry season patterns, but also by the growing impact of heat stress itself on corn, wheat, rice and other staples.
Earth’s ice-covered regions are melting. The vanishing of the Arctic ice cap is changing the heat absorption at the top of the world, and may be affecting the location of the Northern Hemisphere jet stream and storm tracks and slowing down the movement of storm systems. Meanwhile, the growing loss of ice in Antarctica and Greenland is accelerating sea level rise and threatening low-lying coastal cities and regions.
Viruses, bacteria, disease-carrying species like mosquitoes and ticks, and pest species like bark beetles are now being pushed far beyond their native ranges. Everywhere the intricate interconnections crucial to sustaining life are increasingly being pulled apart.
This is the world we’ve made. And in her timely, meticulously researched and well-written book, Kolbert combines scientific analysis and personal narratives to explain it to us. The result is a clear and comprehensive history of earth’s previous mass extinctions — and the species we’ve lost — and an engaging description of the extraordinarily complex nature of life. Most important, Kolbert delivers a compelling call to action. “Right now,” she writes, “we are deciding, without quite meaning to, which evolutionary pathways will remain open and which will forever be closed. No other creature has ever managed this, and it will, unfortunately, be our most enduring legacy.”
Kolbert expertly traces the “twisting” intellectual history of how we’ve come to understand the concept of extinction, and more recently, how we’ve come to recognize our role in it. When mastodon bones were first studied, in 1739, many scientists reasoned that the large and unique bones belonged to an elephant or hippopotamus. But in 1796, the French naturalist Georges Cuvier presented evidence of an entirely new theory: The bones belonged to a lost species from “a world previous to ours.” Cuvier collected and studied as many fossils as he could, eventually identifying dozens of extinct species, and over the next several decades, with the contributions of Charles Lyell and Charles Darwin, extinction evolved as a scientific concept.
Since the origin of life on earth 3.8 billion years ago, our planet has experienced five mass extinction events. The last of these events occurred some 66 million years ago when a six-mile-wide asteroid is thought to have collided with earth, wiping out the dinosaurs. The Cretaceous extinction event dramatically changed the composition of biodiversity on the planet: Marine ecosystems essentially collapsed, and about 75 percent of all plant and animal species disappeared.
Today, Kolbert writes, we are witnessing a similar mass extinction event happening in the geologic blink of an eye. According to E. O. Wilson, the present extinction rate in the tropics is “on the order of 10,000 times greater than the naturally occurring background extinction rate” and will reduce biological diversity to its lowest level since the last great extinction.
This time, however, a giant asteroid isn’t to blame — we are, by altering environmental conditions on our planet so swiftly and dramatically that a large proportion of other species cannot adapt. And we are risking our own future as well, by fundamentally altering the integrity of the climate balance that has persisted in more or less the same configuration since the end of the last ice age, and which has fostered the flourishing of human civilization.
As early as the 1840s, scientists noticed large gaps in the fossil record — time periods in which earth’s biodiversity declined rapidly and could not be explained by a static system. Some scientists theorized that abrupt climate changes had caused past mass extinction events. But in the modern era, three factors have combined to radically disrupt the relationship between civilization and the earth’s ecosystem: the unparalleled surge in human population that has quadrupled our numbers in less than a hundred years; the development of powerful new technologies that magnify the per capita impact of all seven billion of us, soon to be nine billion or more; and the emergence of a hegemonic ideology that exalts short-term thinking and ignores the true long-term cost and consequences of the choices we’re making in industry, energy policy, agriculture, forestry and politics.
“People change the world,” Kolbert writes, and she vividly presents the science and history of the current crisis. Her extensive travels in researching this book, and her insightful treatment of both the history and the science all combine to make “The Sixth Extinction” an invaluable contribution to our understanding of present circumstances, just as the paradigm shift she calls for is sorely needed.
Despite the evidence that humanity is driving mass extinctions, we have been woefully slow to adopt the necessary measures to solve this global environmental challenge. Our response to the mass extinction — as well as to the climate crisis — is still controlled by a hopelessly outdated view of our relationship to our environment.
Fortunately, history is full of examples of our capacity to overcome even the most difficult challenges whenever a controversy is finally resolved into a choice between what is clearly right and what is clearly wrong. The anomalies Kolbert identifies are too glaring to ignore. She makes an irrefutable case that what we are doing to cause a sixth mass extinction is clearly wrong. And she makes it clear that doing what is right means accelerating our transition to a more sustainable world.