According to a new report in the scientific journal Nature, about 41% of amphibians, 26% of mammals and 13% of birds are currently on the verge of oblivion. If things keep going as they have until now, our planet may face the sixth great extinction by the end of the century.
Previously, mass extinctions, defined as the loss of 75% of all species, were caused by natural events, like changing sea levels, non-anthropogenic global warming and asteroid impacts. The last extinction on a mass scale – the Cretaceous-Jurassic extinction event – happened around 66 million years ago and is best known for having wiped out the dinosaurs.
In today’s world, however, the livelihood of animals is mostly threatened by human activities. Scientists think that the continuing spread of agriculture, pollution, introduction of invasive species and overfishing are to blame for the principal part of habitat loss and devastation of marine ecosystems.
“Habitat destruction, pollution or overfishing either kills off wild creatures and plants or leaves them badly weakened,” claims Derek Tittensor, a marine ecologist at the World Conservation Monitoring Centre in Cambridge. “The trouble is that in the coming decades, the additional threat of worsening climate change will become more and more pronounced and could then kill off these survivors.”
Exacerbating the problem is our limited knowledge of the planet’s biodiversity – current estimates of the total number of animal, plant and fungi species range from 2 million to 50 million, while the extinction rate is thought to be anywhere between 500 and 36.000 species per year. “This is the real problem we face,” remarked Tittensor. “The scale of uncertainty is huge.”
And yet, if we keep losing 0.01 to 0.7 per cent of all existing species every year, the next great extinction could befall our planet by the end of this century, although that will depend on where exactly on the spectrum the rate of extinction will fall.
The editorial accompanying this report calls for an urgent and accurate census of the number of animal, plant and fungi species and their rates of extinction to be carried out by the world’s governments and groups like the International Union for Conservation of Nature. This might not be the most exciting undertaking, but it is absolutely vital if we want to protect our planet and the survival of our own species. As the ecologist Paul Ehrlich once said: “In pushing other species to extinction, humanity is busy sawing off the limb on which it perches.”
Original report: Nature 516, 158-161, 11 December 2014. DOI: 10.1038/516158a.