What are the impacts of human activities on tropical rainforest?

Tropical rainforests cover 7% of the world’s land area but contain 50% of all plant and animal species. They provide vital goods and services on a global scale. However, tropical rainforests are being exploited at an alarming rate. Deforestation is the permanent removal of forests to enable the land to be used for something else.

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This is the most widely reported cause of deforestation in tropical rainforests. Trees are cut down to create commercial items such as furniture, paper, doors and household utensils. Many companies would argue that they only cut down some trees but many more are damaged in the process.

With no trees to hold the soil together, heavy rain washes away the soil (erosion). This eroded soil can enter rivers, silting up habitats that fish use for breeding. The removal of trees also disrupts the water cycle – this can lead to some areas becoming very dry with an increased risk of wildfires, whilst other areas become more at risk from flooding. Logging also requires the felling of trees for road construction which further opens up the rainforests for development/destruction.

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The number of cattle ranches in the northern regions of the Amazon have increased significantly; the number of cattle outnumber people by 10 to 1. Around 80% of Brazil’s deforested areas are being used for cattle ranches. It is very popular as it is relatively low risk compared to cash crops such as palm oil plantations. Palm oil is one of the most profitable cash crops for developing countries. It is found in about half of all products sold in supermarkets, from supermarkets from margarines and cakes to shampoos and cosmetics. It is also used to create fuel.

Land is often cleared using the slash-and-burn technique. Burning vegetation produces carbon dioxide, which adds to the greenhouse effect. The ability of the rainforest to store carbon is also reduced at the same time. Without tress to intercept rainfall, more water reaches the soil. Nutrients are washed away so soil fertility is reduced (they usually lose their fertility in 3-5 years). Artifical fertilisers are then added to the soil to improve its fertility and these get washed (leached) into streams threatening wildlife.

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Mineral extraction

Gold, copper, diamonds and other precious metals and gemstones are found in rainforests. Areas are also been surveyed for oil and gas reserves. The money countries make through their mineral wealth give funds for infrastructure projects such as electricity and roads in developing regions. However, there are many environmental problems.

Mining of precious metals often requires heavy machinery and the removal of trees. Heavy chemicals are used to extract and purify the metals which are washed (leached) into streams and rivers, killing wildlife and polluting people’s drinking water. There can also be conflict with local people over rights to land.

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Mass tourism leads to building of hotels in fragile areas and can have a significant negative impact on the relationship between local communities and the government. Tourism can also drive road construction.

Tourists may scare wildlife (e.g. causing nesting birds to abandon their young). They may also damage vegetation and leave behind lots of litter. If tourism is unregulated, a lack of insfrastructure e.g. sewers, can lead to water becoming polluted. However, to build infrastructure trees must be cleared.

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Energy production

Dam building is common along rainforest rivers to produce hydro-electric power. As a result of this, thousands of people are forced to leave their land and large areas of the rainforest are flooded.

The problems dams create for indigenous people include disruption to the natural river system; as a result of silt being trapped behind dams, fewer nutrients are supplied to land dwonstream for the small-scale agricultural practices of local people. Habitats are also destroyed leading to possible extinction of some species.