The basic reasons of deforestation are the followings:
(1) Expansion of Agriculture:
With increase in the demands for agricultural products, more and more land is brought under cultivation for which forests are destroyed, grasslands ploughed, uneven grounds, leveled, marshes drained and even land water is reclaimed. Such an expansion is marked with more ecological destruction. In tropical regions of the world, as much of the mineral material is lodged in the plant biomass, its removal takes away large part of nutrients. The soil becomes poorest thus is unable to support farming for long duration.
(2) Shifting Cultivation:
Shifting cultivation is considered to be another cause for deforestation. In fact shifting cultivation has occurred due to poor fertility of the soil. In this cultivation a small patch of tropical forests is cleared, vegetation, destroyed and burned. Crops are grown as long as the soil is productive, after which the cultivation is abandoned, and a cultivations move on to fresh patch of land.
The abandoned land is allowed to lay as such for long periods during which regret of vegetation took place and natural ecosystem was restored, shifting cultivations thus worked in harmony with nature. The soil is unable to regain its fertility before it is put to use again. This causes degradation of soil and failure of crops after crops. As crops fail more and more land is cleared of forests to be put to similar over exploitation. The overall result is that green forests are being gradually replaced by barren waste land.
(3) Fire Wood Collection:
Majority of rural populations as well as larger number of people living in small towns and cities of developing countries, the only fuel is wood, which's burned to cook food and provide heat in chilly winters. Fire wood collection contributes much to the depletion of tree cover. Denser forests usually produced a lot of combustible material in the form of dead twigs, leaves etc.
There is hardly any need of cutting down live trees in densely wooded localities. However in case of lightly wooded forests, where the pressure demands is usually higher, a slow thinning of wood lands occurs due to regular foraging of villagers. However, the dead woods is actually manufactured, trees are axed their barks girdled and live trees became personal head loads to find their way to local markets.
(4) Timber Harvesting:
Timber resource is an important asset for the prosperity of county. Commercial wood is found ready in national as well as international markets. According to natural forests are being exploited logging or felling of forest trees for obtaining timber is an important cause of deforestation.
Live trees with thick and straight trunks are filled and transported to commercial establishments elsewhere to consumers. In this process large stretches of forests are damaged. The profits from timber trade are more enjoyed by Governments, large companies or affluent contractors, local people get a tiny share in the benefits while axing their own resource base.
Though agriculture has always been concentrated on planes and floors of valleys farming on narrow flat steps cut one after another across the slope or terrace farming is an age old practice. The ever rushing human numbers and their necessities have forced many to go up the mountains slopes for cultivation. More and more slopes are cleared of plants, steps carved out and against many ads cultivation is attempted. After a few crops the productivity declines.