IGCSE Geo Revision – Environmental Risks

IGCSE Geo Revision –  Environmental Risks

7 Mark Case Study Questions

Causes and Effects of Pollution

Human activities may cause water and air pollution. Choose an example which you have studied of either water pollution or air pollution. Describe the causes this pollution and its effects on people and the environment. [7]


  • the discharge of harmful substances into rivers, lakes and seas
  • Nitrate fertilisers are very soluble in water. They are easily washed off fields by rain, and then into rivers and lakes. Because nitrates are soluble they cannot easily be removed from the water.
  • Pesticides used by farmers include herbicides (to kill weeds) and insecticides (to kill insects). These substances may be washed or blown into rivers and lakes.
  • Human sewage is another source of water pollution. If untreated sewage gets into rivers, microorganisms decompose it. They use oxygen from the water for aerobic respiration. As a result there is less oxygen dissolved in water, so aquatic organisms such as fish and insects may be unable to survive.


  • Eutrophication

Eutrophication encourages the growth of algae. These form a green bloom over the water surface, preventing sunlight reaching other water plants. These plants die because they are unable to carry out photosynthesis. Bacteria decompose the dead plants, respiring and using up the oxygen in the water as they do this. The low oxygen levels make it difficult for aquatic insects and fish to live, and eventually the lake may be left completely lifeless.

Local people loses clean water sources, food sources (animals living in the water) and some land animals might decrease in number as they might be closely linked to animals living in the water.

Photo by Riley on Unsplash

Research for all Case Studies

Location: Borneo
Economic activity: Deforestation

General Introduction

Borneo is the third-largest island in the world and the largest in Asia, covering an area of roughly 297,000 square miles. Deforestation is severe in Borneo in the past 5 decades. In 1973 forest covered 75% of the land area in Borneo and this had reduced to 30% by 2010.

Causes of Deforestation

1. Logging

During the 1980’s to 1990’s, logging was taking place in Borneo at a rapid rate. This is from the fact that the government gave some of the land with the rainforest and the best way they could utilise it is to harvest the wood. Eventually logging became illegal in Borneo, but logging still exists on Borneo to this day.

2. Agriculture

One cause of deforestation is agriculture as land needs to be cleared in order to make space for palm oil and pulp plantations. In Indonesia palm oil production has increased from 600,000 hectares in 1985 to more than 6 million hectares by 2007. The continued expansion of these industries will come at the cost of the life of animals, habitats, and ecosystems as a whole.

3. Fuel

A cause of the rapid deforestation of the Borneo Rainforest is the amount of wood fuel needed to be used for cooking, heating and industrial uses. Wood remains the chief source of fuel in rural areas and also contributes to the Urban consumption. Some sectors of the industry in Southeast Asia depend on the fuel wood entirely. Between 1980 and 2000 more round wood was harvested from Borneo than from Africa and the Amazon combined.

Photo by Yi Chun Chen on Unsplash

Effect of deforestation on the local natural environment

1. Lack of oxygen and destruction of ecosystems

Borneo has 5% of all species in the world. Large animals like orangutans and elephants are especially prone to this as they need large areas of land to survive. The destruction of ecosystems has caused species dying out and the decrease of biodiversity. Roads built for tree cutting also affects smaller species as this leads to the separation of habitat ranges.

2. Air pollution (haze)

Palm oil plantations, pulp plantations, illegal logging and the forest fires are the key drivers to deforestation in Borneo. This can lead to even more harmful effects as Palm Oil plantations are burnt once used, causing what we know as haze, which is bad for animals as well as humans. This affects  people in Borneo and around South East Asia. In Palangkaraya, the capital and the largest city of Central Kalimantan in Borneo, more than 500,000 people to suffer from respiratory ailments in 2015.

3. Soil erosion

As trees are uproots, and cut down, the earth that is held together by roots can be easily washed away with rain or drainage. This can lead to the destruction of habitats especially plant life on the shrub level of the rainforest. Without soil, they have no nutrients and nowhere to ‘root’ themselves. 

Effect of deforestation on the global environment

1. Lost of world’s biodiversity

Deforestation leads to the loss of biodiversity, not just in Borneo, but all over the world. More than 80% of the worlds species remain only in the tropical rainforest. It is estimated that about 50-100 species are being lost each day. This is because the animals are losing their habitat.

2. Climate change / Global Warming

Destroying the forests mean that more CO2 will remain the atmosphere as there are less trees to absorb it. This will not only alter the climate of the region, but also the average temperature of the whole globe. An enhanced global warming is caused as an excess of sunlight is being trapped inside the the atmosphere of Earth that is thickened due to the emitted CO2. Many animals around the world depend on the wet climate of the tropical rainforests and cooler temperature but with deforestation the forests become drier and hotter, killing many animals from harsh weather conditions.

Effects of deforestation on people in Borneo


Haze is caused by the burning of woods in the process of deforestation. It is detrimental to people’s health. In 2015, haze in Palangkaraya, the capital and the largest city of Central Kalimantan in Borneo, causes more than 500,000 people to suffer from respiratory ailments. Haze also creates conditions that can support many serious pathogens such as malaria and the Nipah virus.

Soil erosion

[The part before about soil erosion]. Soil erosion causes severe impacts on local people. Firstly, from the aspect of agriculture, soil erosion removes top soil which is the most productive part of the soil profile for agricultural purposes, reducing the soil’s ability to store water and nutrients and possibly causes losses of newly planted crops. This will result in lower yields and higher production costs in Borneo.

Also, some toxic substances like nutrients, fertilisers and herbicides or pesticides, causing fish dying off in the water. This causes a loss of food source for people living in the polluted area. Also the fishing industry will be hugely impacted as less fresh fish could be caught in the area.

Cover Photo by Holger Link on Unsplash

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