
The main cause of rainforest destruction or deforestation is human activity. Humans are cutting down rainforests for many reasons, including:

Grazing land for cattle
Many rainforests in Central and South America have been cut down to make room for cattle farming to cut down costs and provide beef at cheap prices to countries such as North America, China and Russia. Clearing for cattle pasture is the leading cause of deforestation in the Amazon and Brazil now produces more beef than ever before.
Agriculture for both small and large farms
Every year thousands of miles of rainforest are burnt for agricultural use. The two main groups responsible for converting rainforest into farmland are poor farmers and corporation.
Poor farmers in many parts of the world rely on clearing rainforest to feed their families. Without access to better agricultural lands, these people use “slash-and-burn” to clear patches of forest for short-term periods of time. Typically, they farm the cleared land for a couple of years before the soil is exhausted of nutrients and they must move on to new patch of forest.
Agricultural companies are clearing more rainforest than ever before, especially in the Amazon where large tracts of rainforest are being converted into soybean farms.
Indigenous Indians also use "slash and burn" farming techniques, but on a small scale. For centuries they have used a sustainable system where, when they finish using one small patch of land, they move away to a different area and allow the forest to regenerate. Since the area cleared is small, the soil does not dry out and therefore the forest clearance is localized and temporary rather than extensive and permanent.
Wood for timber and firewood
One of the leading causes of rainforest destruction is logging. Many types of wood used for furniture, flooring, and construction are harvested from tropical forests in Africa, Asia, and South America.
Vast areas of rainforest are cut in one go (clear felling) and the most valuable trees are selected for timber, leaving the others for wood chipping or charcoal production. The roads that are created in order to cut and remove the timber often lead to further damage.
Local people often rely on harvesting wood from rainforests for fire wood and building materials. In the past such practices were not particularly damaging to the ecosystem. However, today in areas with large human populations, the sheer number of people collecting wood from an area rainforest can be extremely damaging.
Road construction and development
Road and highway construction in the rainforest opens up large areas for development. In Brazil, the Trans-Amazonian highway resulted in the destruction of huge areas of forest by poor colonists, loggers, and land speculators. In Africa, logging roads give access to poachers who hunt endangered wildlife as "bushmeat" or meat sold to city dwellers.
Poverty
Poverty plays a major role in deforestation. The world's rainforests are found in the poorest areas on the planet. The people who live in and around rainforests rely on these ecosystems for their survival. They collect fruit and wood, hunt wildlife to put meat on the table, and are paid by companies that extract resources from forest lands.
Most rural poor never have the options that we in Western countries take for granted. These people almost never have a choice to go to college or become a doctor, factory worker, or secretary. They must live off the land that surrounds them and make use of whatever resources they can find. Their poverty costs the entire world through the loss of the tropical rainforests and wildlife. Without providing for these people rainforests cannot be saved.
Mining
The developed nations relentlessly demand minerals and metals such as diamonds, aluminium, copper and gold, which are often found in the ground below rainforests. The rainforests therefore have to be removed in order to extract them. Poisonous chemicals are sometimes used to separate the waste from the minerals, for example mercury, which is used to separate gold from the soil and debris with which it is mixed. These chemicals often find their way into rivers, polluting water supplies which local people depend on, killing fish and other animals that feed on them.
Communities can be thrown off their land to make way for mining and drilling. Sometimes the water from the rivers they use for cooking and washing becomes polluted and they become sick. Fish in the rivers also die, so the communities have less to eat.
Oil Companies
Rainforests are seriously affected by oil companies searching for new oil deposits. This is incredibly damaging as often large roads are built through untouched forests in order to build pipelines and extract the oil. This encourages settlers to move into pristine forests and start ‘slash-and-burn’ farming or cutting more timber for sale or the production of charcoal.
Once established, the oil pipelines which transport the oil can rupture, spouting gallons of oil into the surrounding forest, killing wildlife and contaminating the water supplies of local villages.
Dams
Hydroelectric dams are built on rivers in rainforests to provide electricity. Once the dam is built, a large area of rainforest has to be flooded by the reservoir of water behind the dam. The people who live there have to be moved. In Brazil there have been large demonstrations by the tribal rainforest people against plans for building dams in the rainforest. This has resulted in some of the dams not being built.