BRASILIA, Brazil -- Scientists say the shrinking Amazon rain forest may soon be unable to absorb the tons of greenhouse gases spewed into the atmosphere every year from fires set by farmers.

So far, the jungles are the world's largest absorber of greenhouse gases. But scientists warn the rain forest could eventually become a net contributor to global warming.

As the forest contracts, it leads to more carbon dioxide because farmers set fires to burn off fast-growing brush and replenish the soil. Increased carbon dioxide fuels fears of global warming

The Amazon is disappearing rapidly. Last year, more than 9,000-square miles of rain forest were cut down. The Amazon rain forest is the world's largest remaining tropical wilderness.

The findings are being presented this week at a scientific conference in the Brazilian capital.