Aerial view showing deforestation along both sides of the Trans-Amazonian highway, as it runs through Brazil's Amazonas state, in this picture taken on November 17, 2004. Nearly half of Brazil's Amazon rainforest is occupied by human activities and destruction levels are worse than government figures suggest, according to a survey by Brazilian environmental group Imazon. Some 47 percent of the world's largest jungle has either been settled, totally deforested, burned or is being used for mining, logging or agriculture, the study using satellite photos shows. Deforestation of the Amazon, a forest covering an area larger than the continental United States, hit its second-highest level ever last year as ranchers, farmers and loggers cleared an area larger than the U.S. state of New Jersey. PHOTO - REUTERS

PRAGUE - Demands by the United States and other wealthy nations to delay the phasing out of a pesticide that depletes the ozone layer threaten to unravel a key global environmental treaty. Experts and officials attending a United Nations sponsored meeting on substances that deplete the ozone layer said last Thursday the Montreal Protocol is at risk because of differences over quotas on the use of methyl bromide, used mainly in fumigating soil. Under the treaty, signed in 1987 and hailed as one of the most effective environmental treaties ever, the use of methyl bromide was to be phased out in developing nations by 2005.

But the United States, the world's largest user of the chemical, is asking last week's meeting in Prague to allow it "critical use exemptions", a move derided by experts as a step backward in the treaty. "The U.S. is not alone ... Other countries are also seeking overly large exemptions. But the U.S. exemptions and non-complying domestic actions stand out," said David Donegir, a former U.S. negotiator on ozone depleting substances during the Clinton administration, now policy director at the NRDC Climate centre.

Methyl bromide is considered an extremely effective pesticide and is used on crops as varied as cut flowers, strawberries and tomatoes. But it also depletes the ozone, and is partially to blame for a hole that has appeared in the layer which protects the earth from harmful amounts of ultra violet radiation from the sun. Damage to the ozone layer results in increased rates of skin cancer and eye cataracts.

Analysts at the meeting say the hole in the ozone layer shrank by 20 percent last year and could be repaired by 2050 if targets are met.

Under pressure from the agriculture lobby, the U.S. is looking for an exemption to use nearly 9,000 metric tonnes of the chemical -- more than the country used in 2003 -- in both 2005 and 2006. Claudia McMurray, the chief negotiator for the U.S. at the Prague meeting told Reuters she hopes a deal can be reached, with progress already made on the 2005 quota though a large gap exists on the 2006 quota. "We are in full compliance with the Protocol," she said. "We've got to a point where there are no technically and economically feasible alternatives available and seven, eight years ago all the parties agreed that in that case, there should be an exception. That's what we are making use of."

The move has angered developing nations who are battling to phase out use of the chemical by 2015 despite having far fewer resources at hand than countries such as the U.S.. Officials fear that if the U.S. is allowed to slide on its commitments, others will follow suit. "Maintaining the integrity of the Protocol is paramount. Otherwise, the world community is left with only a partial success towards a declining level of this ozone depleting substance," said Klaus Toepfer, Executive Director of the United Nations Environment Programme (UNEP). "This could have consequences beyond the ozone layer, including all our goals and plans for sustainable development." Reuters