November 25, 2011 2:47 pm

Mass extinction: Humans could join list of threatened species

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It is 65m years since an asteroid is believed to have wiped out the dinosaurs, along with three-quarters of the species in existence at the time. Now, some scientists believe we are in the middle of another period of mass extinction and this time it could include us.

In 1953, there were about 2.5bn people on earth. Today there are 7bn. We have nearly trebled our numbers in half a century.

Mankind’s expansion has led to overexploitation of natural resources, causing a series of potentially devastating effects, including climate change, ocean acidification, ozone depletion and the spread of invasive flora and fauna.

Douglas Crawford-Brown, director of the Cambridge Centre for Climate Change Mitigation Research in the UK, estimates the earth is losing about 20,000 species a year: “The real cause of this loss of diversity is habitat destruction, driven by the number of people and how much they’re consuming.”

His view is shared by Prince Charles, who referred to himself as a member of an “endangered species” in his inaugural speech as president of the Worldwide Wildlife Fund in September.

He said that without biodiversity, which is severely threatened, we will not be able to survive, and he called for a “sustainability revolution” that would transform the world economy, so that growth does not come at the expense of nature.

However, not everyone takes such an extreme view. While civilisation as we know it may collapse, complete extinction of the human race is unlikely, says Niles Eldredge, curator emeritus at the American Museum of Natural History, New York. “The species would probably cling on, rather as in the Amazon there are still tribes speaking languages related to those of the Mayans and the Incas.”

Dr Eldredge suggests the “system” would collapse first, as happened in ancient Egypt, Greece, and Rome.

“On the other hand, nobody could imagine extinction of the passenger pigeon in the US – there were millions,” he points out. The last died in a Cincinnati zoo in 1914, and the same almost happened to American bison, which, from millions in the 19th century, at one point fell to a few hundred individuals.

“We can’t say just because there are 7bn people it would be impossible to erase them.”

Scientists believe the planet could support up to 13bn or 15bn, possibly even more. But protecting the human race is partly a matter of sharing resources more equally, says David Nally, geography lecturer at Cambridge university, UK.

“The number of obese is higher than the number of starving, and there is lots of surplus; the amount of waste in the US alone would be enough to feed the world’s malnourished.”

Dr Eldredge agrees the distribution of wealth needs to be more even. “In the mid-1990s, Americans had more than their share of the world’s resources, and now they have more – and wealth is now concentrated in a smaller percentage of the US population.”

Although the Horn of Africa is rich in minerals such as diamonds, gold and uranium, its land is being bought by countries such as Yemen, Saudi Arabia and China for their own use. So resources are not being used for the benefit of local people.

Legislation is needed to protect farmland, for example by requiring the use of crop rotation and natural means of fixing nitrogen in soil, says Mr Nally. “We need regulations so resources can’t be pillaged with impunity.”

A different economic approach is needed, he says. For example, he suggests the ending of agricultural subsidies in rich countries that make farming uneconomic in the developing world. Companies selling pesticides and fertilisers say they are essential to feed the world’s population, However, Mr Nally says: “But in costing such systems, we don’t take into account the destruction of habitats or how nitrogen causes acidification when washed into lakes, rivers and the sea.” He adds: “The good news is that if we can have a negative impact, we can also have a positive one.”

Economic prosperity, along with education and a culture of women working, tends to lead to a reduction in birth rates, he points out.

There are promising signs. Mr Crawford cites financial incentives being introduced to stop the burning of forests to plant crops. “The European Union has taken a big lead in this, and the UK has tried hard too, with programmes that pay people to keep virgin forests in the Pacific Islands.”

There are programmes that encourage farmers to plant diverse crops rather than the same few strains of rice, corn and wheat. It is difficult ensure funds end up in the right place, but progress is being made, Mr Crawford says.

He is not convinced that we are facing the sort of mass extinction that would follow an asteroid hitting Earth. That goes beyond what science can determine, he says, but loss of biodiversity deserves just as much attention as climate change.

For the developed world, protecting biodiversity tends to mean nature conservation, saving pandas and tigers, says Dr Crawford. “But for the vast majority of the 4bn people living at the bottom of the economic pyramid, in aching poverty, when the ecosystem is damaged it affects their livelihood.”

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