An estimated 15 percent of Brazil's huge Amazon rainforest has been destroyed with most of the deforestation occurring during the past 30 years. Deforestation, water, pollution, and other factors are adversely affecting the Amazon environment.
About 550,000 square kilometers of the Amazon jungle have been deforested during the past 30 years, as new roads have brought in farmers who have cleared the land of trees. Using the slash and burn technique - cutting and burning the trees and vegetation - they plant manioc, corn, and other crops.
But much of the land in the Amazon is not suitable for agriculture, because it no longer receives the nutrients that were part of the recycling process that existed when the forest was still standing. Instead, after a few harvests, the acidic soil turns barren and farmers are forced to move on to clear new patches of jungle.
But this process of deforestation is further aggravated; even when patches of primary growth forest remain untouched amidst cleared areas. Scientists are finding that these islands of trees, or forest fragments, are very vulnerable.
Heraldo Vasconcellos coordinates a joint project of the U.S. Smithsonian Institution and Brazil's National Amazonian Research Center, known as INPA, to study the process of forest fragmentation. Mr. Vasconcellos says he and other scientists have found that forest fragments do not survive very well.
"What happens is that once you isolate these fragments you find that wind from the outside, from the pasture areas, blows into the forest and because the trees have shallow roots there is a kind of knockdown effect," Mr. Vasconcellos says. "So you have a lot of trees, especially those near the border of the fragments, that die and as a result you have other trees coming and growing to replace (them). But usually these are what we call 'pioneer species'; species that are pre-adapted to go into large gaps. So you have in fact a change in the structure of the forests, and also you have a change in species composition. You lose species that are typical from the primary forest, and you gain species that are more associated with secondary forest."
These species gradually take over, replacing the deep forest trees that eventually die.
The impact on animal and insect life is similar; species that live in shady, humid habitats disappear. Mr. Vasconcellos says their studies show that of seven types of birds, only one survives in a forest fragment of one hectare.
The danger of this process of forest fragmentation is that over time potentially valuable species of trees and plants are being lost forever. "If you lose those species you can be losing a lot of information that could be helpful for medicine or things like that," he says. "In some cases you can lose the function of the forest. For instance, if you lose a key pollinator and a given tree really depends on that, then you will lose the tree species as well. So you have a cascade effect as well that tends to multiply."
Increased population in the Amazon also damages the environment by producing pollution, especially water pollution. Sewage and chemical waste from industries are the main culprits. Geologist Joao Augusto Dantas says they pollute the small streams and rivers around the Amazon's major towns and cities. But Mr. Dantas, who specializes in water issues at the INPA in Manaus, says the huge volume of water flowing in the Amazon River, about 200,000 cubic meters per second, washes away these pollutants.
Still, he expresses concern about the problem. "When you talk about the big rivers, they are in very good health. But the smaller ones are almost dead in the big cities, and I think something has to be done for those small rivers," Mr. Dantas says.
The vast waters of the Amazon could become a more precious resource in the future, which is why Mr. Dantas believes it must be better protected. "The Amazon River is in good health for now, but this should not be a motive to be careless with nature. I think all efforts must be made to preserve this, and knowing that water will be the best merchandise for this century. The century that has just begun will be the century for water," he says.
Water pollution, deforestation, wildfires, and climate changes are all affecting the Amazon environment. Immense, vast stretches of rainforest still exist, virtually untouched. But population growth and development needs are creating greater pressure on the fragile tropical ecosystem.
Paulo Adario of the environmental organization Greenpeace says the future of the Amazon will depend on public awareness, both in Brazil and internationally. "At the end of the day, who can save the Amazon are not environmental organizations like Greenpeace. It is the population, the public. We are the pushers, we form the armies, but the final decision will be taken by the Brazilian population and by the international audience," he says.
While the Amazon rainforest is in no danger of disappearing anytime soon, it is clearly under siege, a siege whose strength will only increase over time.