ABO EBAM, NIGERIA — In the gloomy shade deep in Africa's rain forest, the noontime silence was pierced by the whine of a far-off chain saw. It was the sound of destruction, echoed from wood to wood, continent to continent, in the tropical belt that circles the globe.
From Brazil to central Africa to once-lush islands in Asia's archipelagoes, human encroachment is shrinking the world's rain forests.
The alarm was sounded decades ago by environmentalists, but was mostly unheeded. The picture, meanwhile, has changed: Africa is now a leader in deforestation. The numbers have changed: U.N. specialists estimate 60 acres of tropical forest are felled worldwide every minute, up from 50 a generation back. And the fears have changed.
Experts still warn of extinction of animal and plant life, the loss of forest peoples' livelihoods, soil erosion and other damage. But scientists today worry urgently about something else: the fateful feedback link of trees and climate.
Global warming is expected to dry up and kill vast tracts of rain forest, and dying forests will feed global warming.
"If we lose forests, we lose the fight against climate change," declared more than 300 scientists, conservation groups, religious leaders and others in an appeal for action at the U.N.-sponsored climate conference in Bali, Indonesia, in December.
The burning or rotting of trees that comes with deforestation -- at the hands of ranchers, farmers, loggers -- sends more heat-trapping carbon dioxide into the atmosphere than all the world's planes, trains, trucks and automobiles. Forest destruction accounts for about 20% of man-made emissions, second only to burning of fossil fuels for electricity and heat. Conversely, healthy forests absorb carbon dioxide and store carbon.
"The stakes are so dire that if we don't start turning this around in the next 10 years, the extinction crisis and the climate crisis will begin to spiral out of control," said Roman Paul Czebiniak, a forest expert with Greenpeace International. "It's a very big deal."
The session in Bali may have been a turning point, paving the way for negotiations in which nations may fashion the first global financial plan to compensate developing nations for preserving their forests.
The latest data from the Food and Agriculture Organization, or FAO, helped spur delegates to action.
"Deforestation continues at an alarming rate of about 13 million hectares [32 million acres] a year," the U.N. body said in its latest "State of the World's Forests" report.
Because northern forests remain essentially stable, that means 50,000 square miles of tropical forest are being cleared every 12 months -- equivalent to that of Mississippi or more than half of Britain's cover. The lumber and fuel wood removed in the tropics alone would fill more than 1,000 Empire State Buildings, FAO figures show.
Although South America loses slightly more acreage than Africa, the rate of loss is higher here -- almost 1% of African forests gone each year. In 2000-2005, the continent lost 10 million acres a year, including big chunks of forest in Sudan, Zambia and Tanzania, up from 9 million a decade earlier, the FAO reports.
Across the tropics the causes can be starkly different.
The Amazon and other South American forests are usually burned for cattle grazing or industrial-scale soybean farming. In Indonesia and elsewhere in southeast Asia, island forests are being cut or burned to make way for giant plantations of palm, whose oil is used in food processing, cosmetics and other products.
In Africa, by contrast, individuals are hacking out plots for small-scale farming.
Here in Nigeria's southeastern Cross Rivers state, home to one of the largest remaining tropical forests in Africa, people from surrounding villages of huts and cement-block homes go to the forest each day to work pineapple and cocoa farms. They see no other way of earning money to feed their families.
"The developed countries want us to keep the forests, since the air we breathe is for all of us, rich countries and poor countries," said Ogar Assam Effa, 54, a tree plantation director and member of the state conservation board.
"But we breathe the air, and our bellies are empty. Can air give you protein? Can air give you carbohydrates?" he asked. "It would be easy to convince people to stop clearing the forest if there was an alternative."
The state, which long ago banned industrial logging, is trying to offer alternatives.
Working with communities like Abo Ebam, near Nigeria's border with Cameroon, the Cross Rivers government seeks to help would-be farmers learn other trades, such as beekeeping or raising fist-sized land snails, a regional delicacy.