When the human population was smaller, people lived in small communities, so the effects of their activities were small and localised. A rapid increase in the human population and an increase in the standard of living, have lead to widespread damage of the environment.

Raw materials, including non-renewable energy resources, are rapidly being used up.

More waste is being produced and unless this is properly handled, it will cause more pollution.

Humans are destroying habitats and reducing the amount of land available for other organisms by building, quarrying, farming and dumping waste.

Back to top

Modern day farming affects the environment in many ways.

Trees and plants are often removed to allow the use of large machinery which makes crop growing more economic.

However, this destroys habitats and upsets the feeding relationships in food webs.

Farmers use pesticides to kill pests such as weeds, insects and rodents. They increase food production but can kill other wildlife. They also contaminate food for human consumption.

Pesticides may be washed into water supplies and contaminate drinking water.

Fertilisers are used to add nutrients to the soil to improve plant growth.
These can also be washed out of the soil into lakes and rivers and can pollute drinking water supplies.

Back to top

Pollution of water by fertilisers may cause eutrophication.

The fertiliser causes rapid growth of plants in the water.

These compete for light and many die.

Micro-organisms feed on the dead plants, so their numbers increase.

As there are many micro-organisms respiring, they use up oxygen in the water.

Fish and other aquatic organisms die due to oxygen shortage.

Back to top

The Greenhouse Effect

The greenhouse effect is caused by pollutant gases building up in the atmosphere and preventing heat from escaping to outer space at night. As a result, the earth is gradually getting warmer; this is called global warming.

The main greenhouse gases are carbon dioxide and methane. They absorb much of the energy radiated from Earth and then re-radiate it back to Earth.

The levels of these gases in the atmosphere are slowly rising.

Carbon dioxide is produced when fossil fuels are burnt.

Methane is released by cattle and from rice fields.

An increase of only a few degrees Celsius may cause big changes in the Earth’s climate, upsetting weather patterns and affecting the types of crops that can be grown in different parts of the world.

Polar ice caps may melt, causing the sea level to rise.

Back to top

Acid Rain

Burning fossil fuels may also produce sulphur dioxide and nitrogen oxide gases.

These gases rise up in the atmosphere from factories, power stations and vehicles and dissolve in the water in clouds forming acid. This falls as acid rain.

Acid rain can damage trees directly.

If the water in rivers and lakes becomes too acidic, plants and animals cannot survive.

Acid rain also damages buildings.

Back to top

Other Pollutants

Sewage pollutes the sea and fresh water, unless it is treated properly.

This is a health hazard, but it also upsets the balance of organisms living in the water.

Untreated sewage provides food for micro-organisms and causes eutrophication.

Toxic chemicals are released from industrial plants and by farmers. These can pollute the land and water.

Some toxins can accumulate along food chains until the top predator has very high, often lethal, amounts in its body.

Back to top
Print this page