A stressed world
Biologists call it the sixth extinction. There have been five great mass extinctions in the history of the earth including:
- The Permian extinction 250 million years ago wiped out 70 per cent of all land animals and over 90 per cent of sea creatures. The causes are unclear.
- The Cretaceous extinction 65 million years ago saw the dinosaurs go down. Scientists think this was caused, at least in part, by a massive asteroid off Mexico’s Yucatan Peninsula, which turned the atmosphere into a blast furnace.More than 70 per cent of the earth’s species were lost. It took tens of millions of years to bounce back.
Today’s extinction is different. It’s human-made rather than natural. There is a natural rate of extinction – evolution wouldn’t exist without it.
But what’s happening now is unprecedented.
The International Union for the Conservation of Nature (IUCN) estimates the loss of species today is 1,000 to 10,000 times higher than the natural rate that occurs through evolution. But as ecologists say, we’re all in this together. Humans need clean water, wild spaces, unpolluted air and uncontaminated land.
So do plants, animals and all other forms of life.
Our interdependence has never been clearer.
The IUCN says nearly 40 per cent of all species are threatened. These include:
- A quarter of all mammals
- One in eight birds
- A third of all amphibians and half of all tortoises and freshwater turtles
- More than half of reptiles
- Over 70 per cent of flowering plants
- More than half of all insects
This article is from
the September 2009 issue
of New Internationalist.
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