Humans are so altering Earth's biosphere that an international teamis warning "a state shift" could be just decades away. They don't use the word doomsday, but they come close. "Humans now dominate Earth, changing it in ways that threatenits ability to sustain us and other species," the researchersreport Thursday in the journal Nature. The researchers stress it is not known how close Earth is to aglobal tipping point, or if it is inevitable. But they suggest that the planet's ecosystems could shift into anew state within just a few decades or a few generations if humanpopulation and consumption rates continue to soar. "It really will be a new world, biologically, at thatpoint," says lead author Anthony Barnosky, professor ofintegrative biology at the University of California, Berkeley. Or, as Canadian co-author Arne Mooers, at Simon Fraser Univeristyin British Columbia, puts it: "Once the shift occurs, they'llbe no going back." A shift or tipping point is "speculation at this point,"Mooers told Postmedia News. "But it's one of those things where you say: 'Hey, maybe webetter find out,' because if it's true, it's pretty serious." The Nature paper grew out of a 2010 conference that raised plentyof questions about whether humans could trigger a state shift, butfew answers on how to recognize and avoid it. The 22 biologists, ecologists, theoreticians, geologists andpaleontologists who produced Thursday's report reviewed paststateshifts the latest being end of the most recent ice age and the remarkable changes humans are driving on the planet. The climate is warming so fast that the "mean globaltemperature by 2070 (or possibly a few decades earlier) will behigher than it has been since the human species evolved," theysay. And to support the current population of seven billion people,about 43 per cent of Earth's land surface has been converted toagricultural or urban use. The population is expected to hit ninebillion by 2045 and they say current trends suggest that halfEarth's land surface will be altered by humans by 2025. That's "disturbingly close" to a potential global tippingpoint, Barnosky says in a release issued with the report. The studysays tipping points tend to occur when 50 to 90 per cent of smallerecosystems have been disrupted. "I think that if we want to avoid the most unpleasantsurprises, we want to stay away from that 50 per cent mark,"Barnosky says. The "ultimate effects" of a state shift are unknown, butthe researchers suggest it could have severe impact on the world'sfisheries, agriculture, forests and water resources. And they warnthat "widespread social unrest, economic instability and lossof human life could result." Mooers says it is known the biosphere is changing because of humanactivity. "It's a question of whether it is going to bemanageable change or abrupt change," he says. "And wehave reason to be the change may be abrupt and surprising." Mooers says he hopes that they are proven wrong. "It would begreat if the naysayers were right, I wouldn't have to worry. "But there is no evidence to suggest they are right," hesays. "The evidence is the opposite." The report is one of series of papers in Nature this week on thehuge challenges facing international leaders and delegatesgathering in Rio de Janeiro on June 20 for the United NationsConference on Sustainable Development, known as Rio+20. It is the20th anniversary of 1992 Earth Summit in Rio. The journal notes there has been little progress on keyinternational commitments made 20 years ago. Instead of curbing carbon emissions to try slow climate change,global greenhouse emissions have soared 45 per cent since 1990. Andgovernments are nowhere near meeting 20-year-old pledges to betterprotect biodiversity 30 per cent of amphibians, 21 per cent ofbirds and 25 per cent of mammals are at risk of extinction,according to the International Union for Conservation of Nature. Twitter.com/margaretmunro. We are high quality suppliers, our products such as Solid Timber Door Manufacturer , Exterior Timber Doors for oversee buyer. To know more, please visits Wood PVC Doors.
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