The Amazon rainforest is the largest in the world and covers nearly 70 percent of Brazil. The rainforest produces about 20 percent of the Earth's oxygen and plays a big role in controlling the climate of the entire planet. The Amazon also is home to more species of plants and animals than any other ecosystem on Earth, 30 percent of the world's total.

About one-fifth of the Amazon has disappeared in the past three decades. The causes are many: Logging, both legal and illegal; construction of homes and roads; and agri-business clearing land to plant crops or graze cattle.

The Brazilian government says the situation is getting better and that federal police are cracking down on illegal logging, in particular. But critics say there aren't enough agents on the ground and that more land needs to be put under federal protection.

Government of Brazil: Ministry of the Environment

NASA: The Amazon

United Nations: State of the world's forests