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Hi, I'm Dave Thurlow for the Weather Notebook. The Brazilian Amazon is considered a biodiversity treasure. It contains more than 30 percent of the world's rainforests and one-fifth of the world's vascular plants. The annual outflow from the river accounts for one-fifth of all the fresh water that drains into the world's oceans.

Despite centuries of effort to overcome nature, people have made little impact on the Amazon. Commercial farming, tourism, and industry play minor but growing roles in the region. Logging and mining companies have targeted the forests for its rare hardwoods and mineral resources.

In the 1990s, The rainforests of the Amazon basin were cleared at an estimated rate of 35 million acres each yearóan area about the size of Wisconsin. The forest quickly covers over cleared areas, but the regrowth is not as diverse as the original cover. This decline in diversity affects animal life and the human population. Animals and plants become rare or extinct, and land becomes scarce.

Mining has also caused problems, such as soil erosion and river contamination with mercury.

After international conservation groups brought attention to the area, the Brazilian government made efforts to monitor development and protect the Amazon's resources. Although the environmental legislation in Brazil is among the most advanced in the world, the laws have been insufficient to stop the devastation. The environmental effects of development and deforestation continue to be difficult issues.

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