people are cutting them down.

No, really, it is because we're logging it AND that there's less 'clean' rain.

They are not rotting, thats for sure

Deforesting - clearing the forests for the purpose of gaining farmland.

The Disappearing Rainforests We are losing Earth's greatest biological treasures just as we are beginning to appreciate their true value. Rainforests once covered 14% of the earth's land surface; now they cover a mere 6% and experts estimate that the last remaining rainforests could be consumed in less than 40 years. One and one-half acres of rainforest are lost every second with tragic consequences for both developing and industrial countries. Rainforests are being destroyed because the value of rainforest land is perceived as only the value of its timber by short-sighted governments, multi-national logging companies, and land owners. Nearly half of the world's species of plants, animals and microorganisms will be destroyed or severely threatened over the next quarter century due to rainforest deforestation. Experts estimates that we are losing 137 plant, animal and insect species every single day due to rainforest deforestation. That equates to 50,000 species a year. As the rainforest species disappear, so do many possible cures for life-threatening diseases. Currently, 121 prescription drugs sold worldwide come from plant-derived sources. While 25% of Western pharmaceuticals are derived from rainforest ingredients, less that 1% of these tropical trees and plants have been tested by scientists. Most rainforests are cleared by chainsaws, bulldozers and fires for its timber value and then are followed by farming and ranching operations, even by world giants like Mitsubishi Corporation, Georgia Pacific, Texaco and Unocal. There were an estimated ten million Indians living in the Amazonian Rainforest five centuries ago. Today there are less than 200,000. In Brazil alone, European colonists have destroyed more than 90 indigenous tribes since the 1900's. With them have gone centuries of accumulated knowledge of the medicinal value of rainforest species. As their homelands continue to be destroyed by deforestation, rainforest peoples are also disappearing. Most medicine men and shamans remaining in the Rainforests today are 70 years old or more. Each time a rainforest medicine man dies, it is as if a library has burned down. When a medicine man dies without passing his arts on to the next generation, the tribe and the world loses thousands of years of irreplaceable knowledge about medicinal plants. The Wealth of the Rainforests The Amazon Rainforest covers over a billion acres, encompassing areas in Brazil, Venezuela, Colombia and the Eastern Andean region of Ecuador and Peru. If Amazonia were a country, it would be the ninth largest in the world. The Amazon Rainforest has been described as the "Lungs of our Planet" because it provides the essential environmental world service of continuously recycling carbon dioxide into oxygen. More than 20 percent of the world oxygen is produced in the Amazon Rainforest. More than half of the world's estimated 10 million species of plants, animals and insects live in the tropical rainforests. One-fifth of the world's fresh water is in the Amazon Basin. One hectare (2.47 acres) may contain over 750 types of trees and 1500 species of higher plants. At least 80% of the developed world's diet originated in the tropical rainforest. Its bountiful gifts to the world include fruits like avocados, coconuts, figs, oranges, lemons, grapefruit, bananas, guavas, pineapples, mangos and tomatoes; vegetables including corn, potatoes, rice, winter squash and yams; spices like black pepper, cayenne, chocolate, cinnamon, cloves, ginger, sugar cane, tumeric, coffee and vanilla and nuts including Brazil nuts and cashews. At least 3000 fruits are found in the rainforests; of these only 200 are now in use in the Western World. The Indians of the rainforest use over 2,000. Rainforest plants are rich in secondary metabolites, particularly alkaloids. Biochemists believe alkaloids protect plants from disease and insect attacks. Many alkaloids from higher plants have proven to be of medicinal value and benefit. Currently, 121 prescription drugs currently sold worldwide come from plant-derived sources. And while 25% of Western pharmaceuticals are derived from rainforest ingredients, less than 1% of these tropical trees and plants have been tested by scientists. The U.S. National Cancer Institute has identified 3000 plants that are active against cancer cells. 70% of these plants are found in the rainforest. Twenty-five percent of the active ingredients in today's cancer-fighting drugs come from organisms found only in the rainforest. Vincristine, extracted from the rainforest plant, periwinkle, is one of the world's most powerful anticancer drugs. It has dramatically increased the survival rate for acute childhood leukemia since its discovery. In 1983, there were no U.S. pharmaceutical manufacturers involved in research programs to discover new drugs or cures from plants. Today, over 100 pharmaceutical companies and several branches of the US government, including giants like Merck and The National Cancer Institute, are engaged in plant research projects for possible drugs and cures for viruses, infections, cancer, and even AIDS. Rainforest Action Experts agree that by leaving the rainforests intact and harvesting it's many nuts, fruits, oil-producing plants, and medicinal plants, the rainforest has more economic value than if they were cut down to make grazing land for cattle or for timber. The latest statistics show that rainforest land converted to cattle operations yields the land owner $60 per acre and if timber is harvested, the land is worth $400 per acre. However, if these renewable and sustainable resources are harvested, the land will yield the land owner $2,400 per acre. If managed properly, the rainforest can provide the world's need for these natural resources on a perpetual basis. Promoting the use of these sustainable and renewable sources could stop the destruction of the rainforests. By creating a new source of income harvesting the medicinal plants, fruits nuts, oil and other sustainable resources, the rainforests is be more valuable alive than cut and burned. Sufficient demand of sustainable and ecologically harvested rainforest products is necessary for preservation efforts to succeed. Purchasing sustainable rainforest products can effect positive change by creating a market for these products while supporting the native people's economy and provides the economic solution and alternative to cutting the forest just for the value of its timber

I'd say they're cutting the forest down for pasture land. Logging is another reason. Big trees bring big profits.

greed

They are often referred to as the womb of life and home to about 50 -90% of the earth’s species and yet, nearly half of the world's species of plants, animals and microorganisms will be destroyed or severely threatened over the next quarter century due to rain forest deforestation. Earth’s greatest biological treasures, our rain forests are disappearing. Innumerable forest-dwelling people live in or depend on rain forests, worldwide, important food crops have been developed from rain forest species. Ecologically, they have been defined as multi-storied closed, broad leaved forest vegetation and yet today, what covered 14% of the earth’s land surface, the figures have now come down to an alarming 6%. So why are we losing about one and one-half acres of rain forest every second? Unfortunately, it is the short-sightedness of governments, multi-national logging companies and land owners, who for their own gain, seemingly rampage the rain forests for timber and thereby overlook the long term alarming consequences. According to experts, by losing about 137 plant, animal and insect species every day and by the disappearance of rain forests, we will also deprive ourselves the access to potential cures for life-threatening diseases. Presently, there are 121 prescription drugs sold worldwide that come from plant-based sources. Furthermore, 25% of Western pharmaceuticals use rain forest ingredients and scientists have tested less than 1% of these tropical trees and plants. As rain forests have been destroyed, so too have native tribes, who could have provided a mine of information on their knowledge of the medical value of rain forest species. As a result, what could have in fact been irreplaceable knowledge for man’s advantage is being destroyed by man himself.The Amazon Rain forest recycles carbon dioxide into oxygen and provides more than 20 percent of the world's oxygen. Furthermore, more than half of the world’s estimated 10 million species of plants, animals and insects live in the tropical rain forests and at least 80% of the developed world’s food originated in the tropical rain forest, which includes a wide variety of fruit and vegetables. Furthermore, 70% of the 3000 plants found in the rain forest, have been found to be effective against cancer cells and 25% of the active ingredients in today’s cancer drugs come from organisms found only in the rain forest.Scientists today are actively involved in plant research projects, for possible drugs and cures for viruses, infections, cancer and AIDS, plants that can be found in the rain forest. Concerns over bio-diversity loss are not new, yet knowledge about the world flora and fauna are almost impossible to obtain due to the reckless destruction of forests, and with them a countless species of plants and animals.Meanwhile, commercial logging harvests timber from forests with the intent to sell the product, yet it leaves behind the most flammable portions of the trees, the needles and limbs on the ground, which in the long run can adversely affect fire behavior for years to come. Furthermore, reduction of tree canopy exposes the forest floor to the forces of nature, causing surface fuels to be hotter and drier. This in turn can result in the faster rate of fire spreading, greater flame lengths and more erratic shifts in the speed and direction of fires. Greed is the basic cause. Best regards.

The simple answer to this is in one word, GREED!

Simply put, the trees are being cut down at a rate that is faster than they can grow back.

one reason is that within the forest there are trees worth tens of thousands of dollars each. Slash and burn just to get to one mahogany. People kill each other over it. The Amazon is a deadly place.