Deforestation is a consequence of over-exploitation of our natural ecosystems for space, energy and materials. The basic reasons for such extensive deforestation are:
(1) Expansion of Agriculture:
Expanding agriculture is one of the most important causes of deforestation. As demands on agricultural products rise more and more land is brought under cultivation for which forests are cleared, grass-lands ploughed, uneven grounds leveled, marshes drained and even land under water is reclaimed. However, this expansion is usually marked with more ecological destruction than rationality. Governments often distribute land under forests to landless people, instead of redistributing already established farm-lands, howsoever, wasteful, unequal and unjust the distribution of ownership of land may be.
During the process of clearing the land precious timber is simply burned. Ghana's 80% forests have disappeared but only 15% timber was harvested. Similarly in Brazil, little timber was extracted before the forests were burned for clearing the land.
Nothing is done to assess the fertility of the forest soil before clearing it for farming. In tropical regions of the world as much of the mineral material is lodged in the plant biomass, its removal takes away a large part of nutrients. The soil being poorer is unable to support farming for long durations. Once agriculture fails, the cleared land is put to use as cattle ranches which too is a hopeless business. The bared soil is subjected to massive erosion and degradation.
The Brazilian Government began the construction of Trans-Amazon Highway in 1970 in hope to colonize its largely empty Amazon basin which was covered with lush green tropical forests. But it was soon realized that apparent fertility of lush green jungle soil was an illusion. Crops after crops failed. Roads were washed away. Newly settled communities disintegrated and high hopes that the Amazon basin shall feed the hungry millions of the world were dashed (Skilling and Tcheyen 1979).
(2) Extension of Cultivation on Hill Slopes:
Outside humid tropical zone, in most of the third world countries, major forests often occur on hill tops and slopes. Though agriculture has nearly always been concentrated on plains and floors of valleys, farming on narrow flat steps cut one after another across the slope or terrace farming is an age-old practice. It has never been extensive because of the gruelling labour and low productivity.
However, the ever rising human numbers and their necessities have forced many to go up to mountain slopes for cultivation. More and more slopes are cleared of plants, steps carved out and against many odds cultivation is attempted. After a few crops the productivity declines and torrential sub-tropical rains carry down massive quantities of precious top soils to streams and rivers. While denuding hill slopes, the silt and sediments settle further down raising stream bottoms and river beds aggravating the flood situation.
(3) Shifting Cultivation:
Shifting cultivation or Jhum is often blamed for destruction of forests. In fact it is poor fertility of soil which has given rise to such a pattern of farming. A small patch of tropical forest is cleared, vegetation slashed, destroyed and burned. Crops are grown as long as the soil is productive, after which the cultivation is abandoned and cultivators move on to fresh patch of land.
The abandoned land was allowed to lay fallow for long periods during which regrowth of vegetation took place and natural ecosystem was restored. Shifting cultivators, therefore, worked in harmony with nature. However, the demands of growing population have shortened the fallow periods drastically. 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. In Indonesia large number of people who have migrated from Java and other crowded islands have turned to shifting cultivation. Farming is attempted on cleared patch of soil before it is able to regain fertility. As crops fail more and more land is cleared of forests to be put to similar over-exploitation. The overall result is that lush green forests are being gradually replaced by barren waste land (Eckholm, 1991).
The influx of shifting cultivators in water-shed around Panama Canal has caused extensive soil degradation resulting in large-scale erosion of the soil. Future utility of Panama Canal and the Panama City's water supply system are threatened by massive deposits of silt and sediments. The Government has launched massive programme of reforestation of the water-shed around Panama Canal (Lawrence; 1978).
(4) Cattle Ranching:
Large areas of tropical forests in Central and South America have been cleared for use as grazing land to raise catties and cash in on the lucrative beef exports to USA. But | in these cases too, the problem of poor productivity of tropical soils makes the venture non-viable The soil degenerates within a short span of time due to over-grazing and massive soil erosion occurs, Cattle ranching has done much damage to the tropical forest cover in South and central America (Fearnside 1980, Parson 1976)
(5) Firewood Collection:
To majority of rural population and a large number of people living in small towns and cities of developing countries, the only fuel is wood which is burned to cook food and to provide heat in chilly winters. Firewood collection contributes much to the depletion of tree cover, especially in localities which are lightly wooded. Denser forests usually produce 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 the case of lightly wooded forests, where the pressure of demand is usually higher, a slow thinning of woodland occurs due to regular foraging of villagers. In Madhya Pradesh, India, a recent observation revealed that felling of small trees for use as firewood and timber exceeds fresh plant growth. In some places in the state, the Government! Allows people to collect head loads of dead wood from forests for personal use.
However, deadwood is actually manufactured, trees are axed, and their barks girdled and live trees become personal head loads to find their way to local markets. If the present trend continues, within twenty years, it is feared that half of the State which has the largest area under forests in India, will become treeless (Tomarand Joshi 1977).
Outright felling of live trees to meet firewood and charcoal requirement is common in lightly! wooded areas in many countries. In Upper Voltas, Sudan, Nigeria etc. well organized gangs exist which cut live trees in widening circles around towns and cities, illegally convert them into charcoal for sale in cities. In Sudan authorities have to use armed guards to protect live trees and armed clashes are common.
(6) Timber Harvesting:
Timber resource is an important asset for a country's prosperity. Commercial wood finds ready national as well as international markets. As a consequence of which natural forests are being mercilessly exploited. Logging or felling of forest trees for obtaining timber is an important cause of deforestation in third world countries.
Live trees with thick and straight trunks are felled and transported to commercial establishments elsewhere, to consumers who are ready to pay. In the process large stretches of forests are damaged and the system which could have provided resources worth much more to the local people is disrupted. Ironically the profits from timber trade are enjoyed by Governments, large companies or affluent contractors. Local people get a tiny share in the benefits while axing their own resource base.
Commercial logging in tropical countries usually involves felling of trees of only selected species which fetch better prices. This process of creaming or removing a few selected trees amidst dense vegetation on rather a delicate soil causes much more destruction than the actual number of trees or the volume of timber taken out would suggest.
In a study in Indonesia, it was found that the logging operations destroyed about 40% of the trees left behind. In many third world countries logging operations have been observed to lead to a permanent loss of forest cover. Loggers after removing a select group of trees move on to other areas. They are usually followed by others who move into the cut over area hoping to start farming and put down roots. The remaining vegetation is slashed and burned and agriculture is attempted. When cultivation fails it is replaced by cattle ranching or by useless tenacious grasses.
The selective harvesting practiced by loggers leave many forests permanently deficient in valuable plant species. Much of the West Africa has become useless for commercial logging as important plant species required by the loggers are not available. In Philippines, the valuable groups of tall trees (Dipterocarpus sp.) have shrunk from original 16 million hectares in 1960, to about one million hectares left standing in remote regions.
The practice of cutting down larger trees, of the selected species, leaving behind younger ones which can grow into fresh stock to be harvested later may appear rational. In theory such patch should become ready for reharvesting within thirty to forty years. However, in practice none of the loggers leaves the required number of younger trees and the notion that the woodland shall be ready for another valuable timber harvest in forty years appears to be a wistful thinking at its best.
In East Kalimantan, the seat of Indonesia's lucrative timber trade logging firms are required to leave behind 25 select crop trees per hectare but in practice none does so and the entire logged out area degenerates into a useless waste land. Of 17 million hectares of rich tropical forests, about 13 million hectares were marked for logging in 1978 by as many as 100 licensed companies. In Brazil also the select fell system which leaves behind younger plants for natural regeneration is being tried with an intensive replantation drive. However, if we look at the recent history of tropical forest exploitation, it appears that most of tropical timber is being harvested like a non-renewable resource (Johnson and Dykstra, 1978).