Monday, February 10, 2014

The Human Strain

Elizabeth Kolbert, The Sixth Extinction: An Unnatural History

Since multi-celled life began around 600 million years ago, natural history has seen five mass extinctions. Life’s trend line favors greater complexity: more than twice the number of life forms exist today than right before the dinosaurs vanished. Yet five times, the number has contracted violently. Scientists who study and classify life’s profound complexity say we’re now facing a sixth mass extinction, the first caused by one species’ actions.

New Yorker journalist Elizabeth Kolbert takes two tacks in her analysis of extinction. She considers extinction as a philosophical concept and scientific fact, while also exploring current circumstances where entire species are vanishing under human eyes. The results are often astonishing. Our understanding of Earth’s biome continues evolving, but Kolbert cannot escape the consequence that humans, inevitably, change all life around ourselves.

Natural philosophers once couldn’t comprehend the idea of extinction. Whenever explorers encountered bones of vanished animals, they invented extravagant explanations how the bones arrived: Noah’s flood, or mythological creatures, or we’ll find them across the horizon. Even Thomas Jefferson, himself a noted naturalist, couldn’t compass the idea that species might vanish. This even as European colonialism changed environments wherever white plows broke the soil.

But French researcher Georges Cuvier examined the evidence and could only conclude: entire categories of species no longer existed on earth. Cuvier identified mammoths, pterodactyls, giant sloths, and other vanished species. But he didn’t just prove that species had vanished in the past; he proved that species could still vanish today, changing how humans perceive our relationship with nature. Any species could potentially vanish—including, imaginably, us.

Globally, innumerable species now face critical jeopardy. Kolbert travels to witness heroic efforts to preserve the Panamanian golden frog, tropical corals, and complex Amazonian biomes. But extinctions resist easy explanation. Traditional narratives, like global warming, habitat loss, or hunting, prove too simplistic for Earth’s complex, shifting biology. One factor underlies all likely explanations, though: species are vanishing because of human actions. We’re annihilating species we haven’t even identified yet.

Humans pushing other species off the brink is nothing new. Science has demonstrated that ancient “megafauna,” like mastodons and moas, vanished when early humans overhunted them. We probably also exterminated Neanderthals, too. But circumstances have changed today. Humans know the consequences our actions are producing, and have the choice whether to continue. Unlike our ancestors, we can no longer sit back in ignorance, blind to the consequences of our actions.

This makes today’s extinctions different from the past. Each of the “Big Five” had different causes: depletion of breathable air, or global cooling, or the Chicxulub asteroid. Some mass extinctions have happened slowly, and one happened in one violent day. But never before has one species so thoroughly changed Earth’s ecology. Humans so completely dominate Earth today that some scientists recognize a new geological era, beginning around 1750, the Anthropocene.

Essentially, humans aggressively reverse natural history. Earth separated the continents to create separate life spheres; our transportation technologies bring these spheres together, turning ordinary species into invasive weeds. Earth pulled carbon out of the air, creating a temperate, breathable atmosphere; we turn that carbon into fuel, burn it, and create the most carbon-soaked conditions our planet has seen in forty million years. We turn Earth’s clock back.

Kolbert doesn’t completely disparage human activity. Though our consumption has driven many creatures to, or past, the point of extinction, we’ve also worked to prevent that very effect. Professional scientists and interested volunteers strive heroically to prevent extinction. Species long vanished in nature survive because humans persevere. But even this proves Kolbert’s underlying thesis, that human action, not wind and water, now dominates Earth’s surface.

One recalls the invisible morals Lee Van Ham warns about.

Notwithstanding her title, Kolbert admits we aren’t in a sixth mass extinction event. Yet. Though many, many species are critically endangered, and extinctions currently occur far beyond what ordinary biology explains. But growing knowledge and humans’ ability to make moral decisions make reversal of this dismal trend possible. Humans could restore Earth to the unprecedented diversity that life enjoyed relatively recently. The question, then, becomes: will we?

Humans act. That’s our nature. Unlike, say, the tropical trees Kolbert spotlights in one chapter, we don’t just strike balances with nature; we make choices, devise plans, and act. But in our technological we’ve accepted complacency as the price of comfort. Kolbert calls humans to choose against passivity and dedicate ourselves to reversing our destructive ways. The burden lies on us now. Will we listen while we still have time?

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