Facts you may or may not know..

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.
More than 20 percent of the Amazon rainforest is already gone, and much more is severely threatened as the destruction continues. It is estimated that the Amazon alone is vanishing at a rate of 20,000 square miles a year. If nothing is done to curb this trend, the entire Amazon could well be gone within fifty years.
The number of species of fish in the Amazon exceeds the number found in the entire Atlantic Ocean.
There were an estimated ten million Indians living in the Amazonian Rainforest five centuries ago. Today there are less than 200,000.

Positive impacts

We chop down trees so that we can grow:
a) Cattle (for the growing beef demand in America and other countries)
b) Soybeans and corn for the new demand for soy milk and soy products and the new Ethanol demand (Yes, going green actually kills trees, but that doesn’t mean it’s a bad thing)
c) For the lumber industry, because we still need trees for houses, paper, and other needs like it is said below.

Amazon's rain forest

They pretty much all result in desertification. The rainforest has very poor soil that is only maintained with lots of plant cover. When we get rid of the rainforest for our multitude or reasons, the topsoil washes away. Then there are not enough nutrients for more plants to grow. Without plants to hold moisture, there is no extra moisture to evaporate back into the clouds to make rain. So the deforested areas literally turn into deserts and experience lower precipitation.
We mainly deforest the rain forest, which is just chopping down trees for lots of reasons. After the trees are cleared away, the land is only fertile for a brief period of time, so farmers are constantly moving and chopping down more trees. We cut trees down for land also, for houses, and farms etc. We use the trees for lumber, houses, furniture, and paper too. By cutting down all the trees, humans have driven many animals out of their homes into open area, with no protection. This causes extinction of some animals. We also drive natives out too. Like I said previously, the land stops being fertile. Basically lots of negative things. I'm sure that is because there are no trees there anymore it causes floods when it rains, and washes away lots of soil, because there is nothing to hold the soil down anymore. And its just not pretty anymore.