Worsening threats to nature include pollution, climate change and forest clearances to make way for farmland
* Pollution, climate change threaten nature - IPBES report
* Grim trend endangers quality of life for human beings (Updates with comments from chairman, news conference)
By Alister Doyle
OSLO, March 23 (Reuters) - Human activities are causing an alarming decline in the variety of plant and animal life on Earth and jeopardising food, clean water and energy supplies, a U.N.-backed study of biodiversity said on Friday.
Climate change will become a steadily bigger threat to biodiversity by 2050, adding to damage from pollution and forest clearance to make way for agriculture, according to more than 550 experts in a set of reports approved by 129 governments.
"Biodiversity, the essential variety of life-forms on earth, continues to decline in every region of the world," the authors wrote after talks in Colombia. "This alarming trend endangers the quality of life of people everywhere."
Four regional reports covered the Americas, Asia and the Pacific, Africa, Europe and Central Asia - all areas of the planet except the poles and the high seas.
For the Americas, the report estimated that the value of nature to people - such as crops, wood, water purification or tourism - was at least $24.3 trillion a year, equivalent to the region's gross domestic product from Alaska to Argentina.
Almost two-thirds of those natural contributions were in decline in the Americas, it said.
Robert Watson, chair of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), said biodiversity was not only about saving rare butterflies, trees, birds or rhinos.
While that was important, he told Reuters a key message was: "Please stop thinking of biodiversity just as an environmental issue. It's way more important than that".
ELEPHANTS AND MOSSES
Among other economic estimates, the Africa report said the absorption of greenhouse gases by a hectare (2.5 acres) of forest in Central Africa was worth $14,000 a year.
Unless governments take strong action to limit greenhouse gas emissions, "climate change may be the biggest threat to biodiversity" by mid-century, Watson said.
He said U.S. delegates had not challenged findings about man-made climate change, although U.S. President Donald Trump doubts mainstream scientific opinion and plans to pull out of the 2015 Paris climate agreement.
For pollution, eight of 10 rivers around the world with most plastic waste were in Asia. On current trends, overfishing meant there could be no exploitable fish stocks in the Asia-Pacific region by mid-century.
Around the world, ever more animals and plants were under threat from human activities, ranging from elephants in Africa to rare mosses and snails in Europe, the study said.
"By 2100, climate change could ... result in the loss of more than half of African bird and mammal species," said Emma Archer of South Africa, the co-chair of the African assessment.
Rising human populations in many developing nations would require new policies, both to protect nature and to meet U.N. goals of eradicating poverty and hunger by 2030.
In Europe and Central Asia, wetlands have declined by half since 1970, threatening many species.
Amid the gloom, there were some bright spots.
Forest cover had risen by 22.9 percent in China and other nations in northeast Asia between 1990 and 2015. Parks and other protected areas were expanding in many regions, including the Americas and Asia-Pacific.
And populations of animals such as the Iberian lynx, Amur tiger and far eastern leopard were coming back from the brink of extinction thanks to conservation. (Reporting by Alister Doyle; Editing by Andrew Roche)
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