Deforestation

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Deforestation

Introduction

Deforestation is the clearing or cutting down of a forest for human activities such as agriculture. It has been going on for thousands of years, usually in response to population growth and the need for food and wood, which is important as a fuel and building material. In the modern era, deforestation is more extensive in developing countries.

Loss of forests has a number of environmental impacts. It can contribute to climate change, by reducing rainfall and altering the amount of sunlight reflected from Earth’s surface. Deforestation also increases the risk of forest fires by drying out the soil. Tree growth is important for biodiversity and for maintaining the quality of soil. Forests may also absorb considerable amounts of carbon dioxide, helping offset fossil fuel emissions. To reduce these impacts, a more sustainable approach to deforestation is desirable, using forestry practices that can preserve maximum tree cover.

Historical Background and Scientific Foundations

The reduction of areas of forest, known as deforestation, has been going on for at least 8,000 years, for a variety of reasons. The extent to which forest cover is decreasing varies from country to country, and it is widely accepted that Africa and Asia are the regions most affected, with deforestation being concentrated particularly in tropical areas. It is difficult to measure exactly how much deforestation has occurred. Direct methods involve going into the forest and measuring how much has disappeared. Remote sensing involves collecting data by satellite, without actually going into the forest. Remote sensing tends to give lower measures of the rate of deforestation than direct methods.

Remote sensing studies are useful in revealing a global picture of forest cover and patterns of deforestation. This reveals that in developed countries, forest cover is either stable, or even growing. In less developed countries, there is evidence of ongoing deforestation. Original forest still remains in Russia, Europe, and North America. Reforestation occurs either through deliberate re-planting of trees, or by succession, which is regrowth occurring naturally over time when a forest area has been disturbed. The new growth will not necessarily consist of the same species of tree that were originally present.

There are a number of different reasons for deforestation, related to either the trees themselves or the land they grow on. The need to use forests tends to be more pressing in developing countries. Wood has long been used as a source of fuel and as a building material. Globally, wood is a multi-billion dollar industry, accounting for about 2% of the world’s gross domestic product. North America and Scandinavia are important areas where deforestation occurs to harvest timber. Around half of wood harvested is used as fuel, the other half for building, paper manufacture, and other uses. In many African countries, wood is the main source of domestic fuel.

Clearing forests for agriculture is perhaps the most significant cause of deforestation. This is usually done by a slash-and-burn approach, where the farmer burns up the trees and vegetation to create a layer of nutrient ash. However, cleared forest is not nearly as fertile or productive as grasslands. It tends to be used by subsistence farmers in developing countries who cannot afford to buy imported foods or modern agricultural machinery or fertilizers that might allow them to produce a higher crop yield. Deforestation is also sometimes done in tropical regions to plant luxury crops like banana and pineapple which are in demand for export to richer nations.

WORDS TO KNOW

CLEAR-CUTTING: A forestry practice involving the harvesting of all trees of economic value at one time.

REMOTE SENSING: Acquiring data about an area such as forest without coming into contact with it.

SUCCESSION: Regrowth of forest following its disturbance by deforestation.

SUSTAINABLE: Capable of being sustained or continued for an indefinite period without exhausting necessary resources or otherwise self-destructing: often applied to human activities such as farming, energy generation, or the maintenance of a society as a whole.

Property rights can also lead to deforestation. In Brazil, in the 1980s and 1990s, the government granted property rights to areas of forest. Those who settled in the forest established these rights by clearing their area through burning. This led to substantial losses of tropical rain forest in Brazil. Other activities involving deforestation include mining, especially in Central and South America, and building dams, which often destroy forests through flooding. Additionally, these activities may destroy large areas of forest because they are supported by road building. This makes the forest more accessible to further activity, such as agriculture and human settlement.

Impacts and Issues

Deforestation has many impacts. Removal of trees reduces the biodiversity of the forest because so many species, from insects to birds, depend upon them. The species that remain may be affected by the fragmentation of their habitat. They may end up close to a road and thereby become more exposed to wind and rain. Loss of trees lets more sunlight into the forest, which dries the soil out and makes forest fires more likely. Fires emit many fine particles into the air that can upset precipitation patterns by allowing clouds to hold more moisture. Lack of rainfall promotes drought and makes further forest fires more likely. Removal of trees also causes soil erosion, which increases the risk of drought and flooding.

Deforestation also affects climate. Leaves transpire, or lose moisture, and solar energy is used in evaporating this. When a forest comes into leaf, there is often, therefore, a cooling effect. Loss of leaf cover allows more solar energy to warm Earth’s surface.

Forests may also act as a carbon sink. That is, they sequester carbon by absorbing it as carbon dioxide from the atmosphere through photosynthesis. The carbon is then stored, for varying periods of time, in the leaves, trunks, roots, and soil. One hectare of tropical forest can stored about 300-600 metric tons of carbon. Globally, forests can store billions of tons of carbon, which could significantly offset the carbon dioxide put into the air by the burning of fossil fuels. Deforestation may reduce the opportunity to use carbon sequestration to offset carbon emissions.

Deforestation, then, has many negative effects. However, forests do offer many obvious economic benefits in terms of their wood harvest and as a land source. Often the benefits of deforestation are more obvious than the negative effects and some governments promote deforestation by offering economic subsidies for farming there. Since it is highly unlikely that deforestation rates can be slowed down, the best approach might be to at least make it sustainable, so that timber taken is replaced by new growth of wood.

Forestry practices can be made sustainable. Clear-cutting is the traditional approach to harvesting timber where all of the trees with an economic value are taken. This is the cheapest method but selective harvesting, where only a certain number of trees are taken at any one time, has a less damaging impact. Another approach is shelter wood harvesting, where trees are partially cut for their wood, while others are left behind as shelter. Currently, there is no agreement over what the most sustainable approach is, as it likely depends upon local conditions. Consumers can play a part by demanding that products such as furniture be supplied only from sustainable forests.