Causes and Impacts of Deforestation in Tropical Rainforests

Forest clearance and changing rates

Deforestation is the removal of forest so that land can be used for another purpose, such as farming, mining or settlement. It changes more than the vegetation: removing trees also affects soils, water, people and the amount of carbon stored in the ecosystem.

The rate of deforestation describes how much forest is lost over a period of time, often measured in hectares per year. Forest cover is the amount of forest remaining. If the annual rate falls but remains above zero, forest cover continues to shrink, just more slowly.

Rates are not constant. Brazil provides an example of a changing trend: in 2015, President Dilma Rousseff reported a substantial reduction in deforestation, but by 2019, under President Bolsonaro, the rate was increasing again. This illustrates why a period of improvement does not guarantee that forest loss will keep slowing.

Malaysia: a rainforest case study

Malaysia is in South-east Asia, with rainforest on the Malay Peninsula and in the Malaysian states of Sabah and Sarawak on Borneo. Its forests face pressure from farming, timber extraction, mining, energy projects and settlement. These activities often reinforce one another: a road built for one purpose can make further clearance possible.

Farming clears land for food and exports

Subsistence farming mainly supplies food for a farmer’s household. In Malaysia, some farmers use slash-and-burn clearance: vegetation is cut and then burnt to create a cultivated area. Fires can escape beyond the intended plot and damage more forest.

Commercial farming produces goods for sale. In Malaysia, rainforest has been cleared for oil-palm plantations. Palm oil is an important export, so demand for it gives companies an economic reason to convert forest into agricultural land. Unlike a varied rainforest, a plantation dominated by one crop provides a much narrower range of habitats.

The distinction matters: subsistence clearance is driven mainly by household needs, whereas commercial clearance is driven by sales and profit. Both remove forest, but their scale and economic purpose differ.

Logging and roads open up the forest

Logging supplies tropical hardwoods for sale. In Malaysia, selective logging is common: selected valuable trees are removed rather than every tree in an area. However, access roads and settlements associated with logging also require clearance. Illegal logging has occurred in parts of Borneo despite environmental protection policies.

Road building has direct and indirect effects. Trees are removed along the route itself, but the road also allows machinery, workers and settlers to reach previously less accessible forest. This can lead to additional logging, farming and settlement. The total loss can therefore extend well beyond the road corridor.

Mining and energy development

Malaysia’s tin mines require land to be cleared for extraction and for access roads. Mineral extraction creates a demand for both the mine site and its supporting infrastructure. Oil and gas development is another pressure on forest land.

Energy development can remove forest on a large scale. Hydroelectric power uses moving water to generate electricity, but building a dam creates a reservoir that floods land upstream. The Bakun Dam in Sarawak illustrates this trade-off: its reservoir involves around 700 km² of land being underwater. Forest is lost through inundation as well as through construction clearance.

Settlement and population pressures

New settlements need land for homes, roads and services. Their residents also need food, employment and energy, creating further pressure on surrounding forest.

Until 1980, people in Malaysia were encouraged to move from cities to rural areas to reduce pressure on urban areas. This settlement policy led to the clearance of approximately 15,000 hectares of rainforest. It shows how a policy aimed at relieving one problem can create environmental pressure elsewhere.

Population growth increases demand for housing, food and resources. Migration can also increase the population of a particular forest area without being the same thing as national population growth. In both cases, a larger local population can encourage settlement expansion and agricultural clearance.

Economic gains from deforestation

Forest clearance can support economic development. Logging, mining, farming and hydroelectric projects provide jobs, while sales of timber, minerals and agricultural products generate income. In Malaysia, hardwoods and palm oil provide clear examples of goods produced for export.

Roads improve access to markets, and electricity supports households and businesses. Paid employment can raise incomes and improve living standards for some people. These benefits help explain why governments, businesses and households may support development in forest areas.

However, the benefits are not shared equally. Indigenous communities, including Orang Asli and Temiar communities, have faced displacement from their land. Development that creates income for a company or workers may simultaneously reduce another community’s access to food and its ability to maintain its way of life.

Why clearance causes soil erosion

Rainforest vegetation protects the soil. Leaves intercept rainfall, while roots bind the soil together. After clearance, heavy rain reaches exposed ground more directly and the loss of roots makes soil easier to remove.

Water flowing over the surface carries away topsoil. This is soil erosion, and it reduces the land’s fertility. Rainwater can also dissolve nutrients and carry them down through the soil: this is leaching, a different process from the physical removal of soil.

Many rainforest nutrients are stored in living vegetation. Removing that vegetation removes a major nutrient store and reduces the return of nutrients through fallen leaves and decomposition. In Malaysia, exposed soils consequently become more vulnerable to erosion and nutrient loss. Sediment carried into rivers can build up on riverbeds, reducing channel capacity and increasing flood risk.

How deforestation contributes to climate change

Deforestation affects atmospheric carbon dioxide in two connected ways. First, burning cleared vegetation releases carbon stored in it as carbon dioxide. Second, fewer trees remain to remove carbon dioxide from the atmosphere through photosynthesis.

Carbon dioxide is a greenhouse gas. Increasing its concentration strengthens the greenhouse effect and contributes to global climate change. Clearance fires in Malaysia therefore have an effect that extends beyond the cleared area.

There are also local climatic effects. With fewer trees, less water returns to the atmosphere through evapotranspiration. This can reduce rainfall and make local conditions warmer and drier. Habitat destruction and conversion to plantations also reduce biodiversity.

Weighing development against environmental damage

Malaysia demonstrates a genuine trade-off: forest clearance can provide export earnings, employment, access and electricity, but can also damage soils, habitats and the climate, while disrupting Indigenous livelihoods.

The timescale matters. Income from extracting timber may be gained quickly, whereas declining soil fertility can undermine future farming and climate effects extend far beyond Malaysia. A balanced judgement is that deforestation can support economic development, but those gains do not automatically outweigh lasting environmental damage or guarantee benefits for everyone.

Changing rates

• Rate = forest lost per period; cover = forest remaining.
• A lower positive rate still means forest loss.
• Brazil: a substantial fall was reported in 2015; rates were increasing again by 2019.

Malaysia: causes

• Subsistence farming: household food production; slash-and-burn clearance can spread beyond plots.
• Commercial farming: oil-palm plantations produce goods for sale and export.
• Logging: hardwood extraction; access roads and settlements cause further clearance.