tropical rainforests notes - impacts of deforestation
economic impact: destruction of renewable resources
Deforestation can rob a country of potential renewable revenues while replacing valuable productive lands with virtually useless scrub and grassland. Tropical rainforests provide important renewable resources that can significantly contribute to national economic growth on a continuing basis. Although in theory, logging can be a sustainable activity, generating an ongoing source of revenue without diminishing the resource base, especially in secondary forests and plantations, however, most rainforest logging is not sustainable in practice, diminishing the political revenue for tropical countries in the long term. Short-term economic exploitation through deforestation can be devastating to the long-term economy of developing countries, not only by destroying vital ecosystems that afford important services, but also by destroying potential forest products. In fact, the World Bank estimates that governments lose about US$5 billion in revenues annually as a result of illegal logging while overall losses to the national economies of timber-producing countries add up to an additional US$10 billion per yeae.
environmental impact: loss of biodiversity
Deforestation depletes biodiversity by destroying habitats, separating connecting areas of the rainforest from each other, and interfering with plant reproduction. Logging does not simply remove a few trees from the forest. When canopy trees are cut, many smaller forest trees and plants dependent on them for shade or support or moisture vanish. Animals dependent upon trees or other vegetation for food, shelter, water and breeding sites also disappear. Plants in cut-over areas often cannot be pollinated, or their seeds fall upon unsuitable open areas where they cannot survive. Rainforest species which are restricted to relatively small areas and are found nowhere else will disappear when the area is cleared, and consequences of deforestation such as pollution and silting lead to a further decline in biodiversity. One instance would be in Malaysia where more than half of the river fish species disappeared after logging activities. Amphibian populations in tropical areas have also declined or disappeared under the multiple stresses of habitat loss, pollution and disease. Many of the species being lost are vital to the preservation of our ecosystems, or to significant parts of them. Others may have potential value to humans in terms of food or medicine.
environmental impact: climate change
Forests play a huge role in the carbon cycle on our planet. When forests are cut down, not only does carbon absorption cease, but also the carbon stored in the trees is released into the atmosphere as carbon dioxide if the wood is burned or even if it left to rot after the deforestation process. Climate change occurs due to a buildup of carbon dioxide in our atmosphere. If we carry on cutting down the main tool we have to diminish this carbon dioxide build up, we can expect the climate of our planet to change dramatically over the next decades For example, it is estimated that more than 1.5 billion tons of carbon dioxide is released to the atmosphere due to deforestation, mainly the cutting and burning of forests every year. In the Amazon alone, scientists estimate that the trees contain more carbon than 10 years worth of human-produced greenhouse gases.
environmental impact: increased frequency of droughts and floods
Frequent droughts and floods can partly be blamed on widespread deforestation in that particular region. Trees do two processes. They facilitate more water to infiltrate into the ground and they funnel water into underground aquifers where it is stored to supply rivers during drought. Tree roots also hold onto soil, and hence, the loss of ground cover due to deforestation has resulted in flash floods during heavy rainfall, leading to soil erosion. The soil being washed away into rivers cause the river carrying capacity to reduce and hence increasing flood risk. For instance, the energy-produced by the Mangla Reservoir Dam in Pakistan is reduced because of 100 million tons of silt each year, four-fifths coming from the deforested Jhelum River watershed. Silt refers to materials like clay and soil that are carried by running water and deposited into channels and harbours as sediments.
social impact: indigenous people and culture
Tropical forests are home to millions of native people who make their living through subsistence agriculture, hunting and gathering, or through low-impact harvesting of forest products like rubber or nuts. Deforestation in indigenous territories by loggers, colonisers and/or refugees has sometimes triggered violent conflict and can be socially divisive. For instance, the Guarani were one of the first peoples contacted after Europeans arrived in South America around 500 years ago. In Brazil, there are around 51 000 Guarani living in seven states, many others living in neighbouring Paraguay, Bolivia and Argentina. However, in the last century, the Guarani are affected by the loss of almost all their land and suffer a wave of sucide unequalled in South America. In Mato Grosso do Sul where the Guarani once occupied a homeland of forests and plains totalling some 350,000km2. Today they are squeezed onto tiny patches of land surrounded by cattle ranches and vast fields of soya and sugar cane. Some have no land at all and live camped by roadsides.
environmental impact: depletion of water resources
Tropical rainforests are large water catchment areas. For water scarce countries, water catchment areas should be managed properly so as to retain their capacity to supply good quality water all year round. Thus understanding the possible consequences of land use and land cover changes on water resources is a requisite for better water resources management. However, this is not to be as many river catchments are undergoing rapid change mediated by human interference such as deforestation. For instance, between 1973 and 2000, there was a 32% decrease in forest cover and a 203% increase in agricultural cover in the Mara River basin. Other river catchments on the Kenyan side of the Lake Victoria basin have also undergone similar changes. Increased intensity of agriculture and deforestation have been linked to increasing magnitude and frequency of runoff events and reduced infiltration, increased pesticide contamination, erosion and sedimentation of streams and rivers. With the inevitable challenge of climate change amid a rapidly increasing human population, averaging 3% per annum, these problems are likely to be exacerbated, jeopardising environmental management efforts, biodiversity conservation and sustainable social and economic development.