There have been five extinction waves

There have been five extinction waves in the

planet’s history—including the Permian extinction

250 million years ago, when an estimated

70% of all terrestrial animals and 96% of all marine

creatures vanished, and, most recently, the Cretaceous

event 65 million years ago, which ended the

reign of the dinosaurs. Though scientists have directly

assessed the viability of fewer than 3% of the

world’s described species, the sample polling of animal

populations so far suggests that we may have entered

what will be the planet’s sixth great extinction

wave. And this time the cause isn’t an errant asteroid

or megavolcanoes. It’s us.

Through our growing numbers, our thirst for natural

resources, and, most of all, climate change—which,

by one reckoning, could help carry off 20% to 30% of

all species before the end of the century—we’re shaping

an Earth that will be biologically impoverished. A

2008 assessment by the International Union for Conservation

of Nature found that nearly one in four

mammals worldwide was at risk for extinction, including

endangered species like the famous Tasmanian

devil. Overfishing and acidification of the oceans

are threatening marine species as diverse as the

bluefin tuna and reef-forming corals.

Scary for fishermen, yes, but the question arises,

“Why should it matter to the rest of us?” After all,

nearly all the species that were ever alive in the past

are gone today. Evolution demands extinction. Why

should the loss of a few species among millions matter?

Answer: for one thing, we’re animals too, dependent

on this planet like every other form of life. When

we pollute and deforest and make a mess of the ecological

web, we’re taking out mortgages on the Earth

that we can’t pay back—and those loans will come

due. Then there are the undiscovered organisms and

animals that could serve as the basis of needed medicines—

as the original ingredients of aspirin were derived

from the herb meadowsweet—unless we unwittingly

destroy them first.

Forests razed can grow back, polluted air and water

can be cleaned—but extinction is forever. And we’re not

talking about losing just a few species. In fact, conservationists

quietly acknowledge that we’ve entered an

age of triage, when we might have to decide which

species can truly be saved. The worst-case scenarios of

habitat loss and climate change show the planet losing

hundreds of thousands to millions of species, many of

which we haven’t even discovered yet. The result could

be a virtual genocide of much of the animal world.

So if you care about tigers and tamarins, rhinos and

orangutans, if you believe Earth is more than just a

home for 6.7 billion human beings and counting,

then you should be scared. But fear shouldn’t leave

us paralyzed. Environmental groups worldwide are responding

with new methods to new threats to wildlife. Britanica 2010