Deforestation can generate income for farmers, land developers and national economies, but deforestation can have a negative impact on local and global ecologies and ecosystems. The population in most countries is increasing, which puts pressure on local economies to produce more food or clear more land for urban development priorities such as housing and commerce. Cutting down forests not only generates income from the sale of timber, but also clears land for use in development. On the other hand, forests are vital parts of local and global ecosystems. Cutting down forests, especially jungles and rain forests, often threatens species of wildlife and ultimately contributes to dangerous trends such as global warming.
Deforestation is debated in many different countries, but perhaps none so intensely as in Brazil, which is home to the largest part of the Amazon rain forest. This massive forest — about 7 million square kilometers — produces approximately 20 percent of the world's oxygen. Local farmers argue that clearing parts of the rain forest is necessary for them to survive because the land they clear using slash-and-burn techniques is usually only fertile for a few years of intensive agriculture. They must continue to clear more land if they are to continue to farm. But while their local economy depends on deforestation, the Amazon rain forest is an important source of species diversity and atmospheric "scrubbing" for everyone on the planet. If the Amazon is allowed to disappear, its absence could have an enormous negative impact on all life on Earth. So the debate about deforestation must be understood as the tension between the interests of local economies and global ecology.