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  • Geography Optional Notes On – Farming In Temperate Lands – For W.B.C.S. Examination.

    The transformation from tropical forest to crop and pasture land brings about substantial losses of soil fertility and soil erosion. Furthermore, in many tropical rainforest areas, pastures can only be sustained for a short period of up to ten years. Soil nutrients are rapidly depleted after clearing and grasses are soon replaced by less useful vegetation.Continue Reading Geography Optional Notes On – Farming In Temperate Lands – For W.B.C.S. Examination.

    Natural regeneration of forests is quite difficult, especially in large degraded areas. More than 50 percent of the pasture areas in Amazonia have now been abandoned in a degraded state. For the total area of tropical forest, WRI (1994) estimates that 427 million hectares are degraded, most of it as abandoned pasture or fallow after shifting cultivation.

    Plant and animal biodiversity. For the rainforests, data on biodiversity losses are dramatic. Since 1950, about 200 million hectares of tropical forest have been lost, with the result that of some unique plant and animal species, in one of the world’s richest sources of biodiversity have become extinct. Forest areas of Central America have declined from 29 to 19 million hectares, since 1950, although, since 1990, the rate of deforestation in this region has fallen. In Central America in the 1980s rainforests disappeared at the rate of 430 thousand hectares per year but this declined to 320 thousand hectares over the period 1990 to 1994. In South America, the deforestation rate in the 1980s was about 750 thousand hectares per year. It is not known, whether this rate has declined over the last years. 

    Land use. Livestock ranching has often been regarded as the driving force behind the deforestation of tropical rainforests. However, there is increasing evidence that livestock ranching in deforested areas is merely the most obvious symptom of a much more complex degradation process with a variety of driving forces. They are detailed below.

    Road construction leads to accelerated deforestation, and is possibly the single most important direct cause of deforestation. For example, Ledec (1992) found that in Panama, for each kilometre of an all-weather road, between 400 and 1,000 hectares of forest were cleared. Roadside ranchland was sold in Nicaragua at about three times the price of comparable land one day’s walk away (Maldidier, 1993). In Rondonia, Brazil, the paving of an existing road was the main factor in clearing 100,000 km2 of rain forest, and focused, in the early eighties, the world’s attention on this relationship (Myers, 1981). Livestock ranching, with little supervision requirement and few bulky inputs became an attractive activity along these new roads.

    Arable farming, in the rainforest areas, usually takes the form of “slash and burn” agriculture, especially in the forest areas of sub-Saharan Africa and Asia. Several studies (Bruenig, 1991) describe this as the most important mechanism of deforestation in these areas. Overall the area cropped increased over the last two decades. When population pressure is low (less than 30 people per km2), and the area deforested is relatively small, secondary forest climax vegetation can return, thus limiting longer term soil erosion. If population pressure increases further, a downward spiral of declining soil fertility and crop yields emerges. In Central and South America, the total area under crops has remained stable, but slash and burn cultivation continues at the primary forest frontier, and is compensated by desertion of earlier depleted cropping areas, or their conversion into pasture. This conversion of crop land to pasture is common practice, as many ranchers use a crop of corn to generate income for future ranching.

    In Indonesia, transmigration projects (moving people from the over populated areas of Java to the lesser populated outer islands) have often been cited as the principal cause of deforestation. Again, cropping is the first land use and livestock are introduced quite late in the farming system and mainly in environmentally friendly stall feeding systems. Animal agriculture is therefore not one of the leading causes of deforestation. In sub-Saharan Africa, crop production, and especially the expansion of permanent plantation crops, such as oilpalm and rubber, have been major causes of deforestation. Very little tropical rainforest has been converted into ranches on this continent. Forest overexploitation is also an important factor in deforestation, especially in Asia and Africa, where about 20 percent of the areas are over-exploited. Such over-logged areas are then easily converted into shifting cultivation areas. Logging is not important as a cause of over-exploitation in South America (Sharma et al., 1993).

    Relative importance of different pressure factors in deforestation. As in the case of desertification, there have been several quantitative estimates on the individual importance of these factors. However, unlike in the case of desertification, the direct cause is easier to ascertain, making these estimates more relevant. Nevertheless, there are some overlaps, especially as logging is often a precursor for cropping, which in turn often precedes ranching. This means that even in tropical rainforests the cause of environmental damage is hard to apportion. For the record, Table 2.3 provides some estimates. Overall, “slash and bum” agriculture is said to cause 60 percent of the deforestation (Bruening, 1991).

    Policy pressures. Probably more than for any other livestock- environment interaction, inappropriate incentives, land tenure and institutional policies have played a major role in deforestation. land degradation and erosion of biodiversity in the humid tropical areas.

    Technology and policy options

    Many causes for ranching encroachment in rainforest areas have disappeared. Subsidized credit for ranching has been phased out almost everywhere and the overall volume of credit to the sector has declined. In addition, some of the more exogenous factors turned against ranch expansion. Meat exports from Central and South America have declined dramatically and world market prices for beef have dropped over the last decade. All these measures reduced investments by large and urban investors in ranching, and brought down the overall rate of deforestation. However, these changed incentives had little effect on the small and medium producer, and deforestation for crops and small-holder ranching continues. A new look at the policy instruments for these farmers is thus required, as additional action is necessary to halt the still on-going conversion of rainforest into ranches. The following measures have been suggested (Kaimonitz, 1995).

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