Will it be lights out for the human race as the sixth round of mass extinction gathers pace?
According to a study by researchers at Stanford, Princeton and Berkeley universities, “Vertebrates are vanishing at a rate that is 114 times faster than what would be expected without the destructive influence of humans.”
It identifies deforestation, pollution and human-induced climate change as having a domino effect on entire ecosystems, making many species across the world “essentially, the walking dead.” At this rate, it says, “life would take many millions of years to recover and our species are likely to disappear early on.”
Are we then in the middle of a new period of extinction similar to the one which saw off the dinosaurs 65 million years ago, following Earth’s collision with a giant asteroid?
The cataclysmic event threw up so much debris into the atmosphere that it blocked photosynthesis and pushed down the global temperatures, wiping out most of the living systems on the planet.
And that was just one of five extinction cycles Earth has had, all of which were triggered by physical causes like volcanic eruptions or asteroid impacts. The current die-off, though, has a biotic trigger: The humans, who are putting unsustainable stress on the ecosystem by wantonly terraforming, polluting and overexploiting its species.
The new report is hardly surprising, considering that for a long time, evolutionary biologists puzzled over the ‘sudden’ disappearance of several species of large animals that became extinct for no apparent reason.
Be it Australia, North America, or Madagascar, scores of species ranging from mammoths, giant ground sloths, and prong-horned antelopes to the glyptodonts (large armour-bodied mammals) blinked out in less than a thousand years.
Then in 1965 Paul Martin, an American scientist, offered his ‘overkill’ theory to explain the mystery. It held that ‘major continental-scale catastrophes’ were caused by migrating prehistoric humans hunting down large animals into extinction.
This was validated by computer simulations of goings-on more than 13,000 years ago when the first humans traversed Ice Age land bridges to step onto North America.
Computer models also confirm that mass exterminations did occur in Australia, roughly around the time when people first set foot there.
So, the sixth extinction probably began when the first humans migrated out of Africa some 100,000 years ago and spread across the world, disrupting ecosystems in the process. The invention of agriculture some 10,000 years ago gave a leg-up to the extinction drive.
Humans started manipulating other species and also tinkered with ecosystems, for instance, to produce food crops, while exterminating many native plant and animal species.
Sceptics may argue that just as species die, new ones spring up. Never mind if this flies in the face of scientific evidence that it takes 10 million years before biodiversity even begins to resemble what existed before a die off.
Indeed, life on Earth has always been so resilient, bouncing back with amazing vitality once the agent of extinction faded away.
With the Sixth Extinction, however, that agent happens to be us — which means we must change our attitude towards the ecosystem. Else, there will not be any humans around on the planet to declare when the sixth extinction phase is over.
Prakash Chandra is a science writer
(The views expressed are personal)