Negative human impacts

As the human population increases, the volume of waste and pollution that is produced also increases. Polluting an ecosystem harms or kills the organisms that live within it.

In modern society, humans manufacture an increasing number of products and replace them more often. This is not sustainable - many natural materials, including fossil fuels, will soon run out and many people argue that there is already too much waste.

Water pollution

In some instances, toxic waste or sewage can end up in, or be discharged into streams, rivers and lakes, causing damage to aquatic life and serious illness in humans that may drink the contaminated water.

Some farmers use too many fertilisers, which can run off fields during heavy rain. This can pollute nearby streams and rivers leading to eutrophication.

Eutrophication and how it affects ecosystems.

Air pollution

Combustion of fossil fuels and other fuels releases carbon dioxide. This contributes to the greenhouse effect, producing global warming and leading to climate change.

Combustion of fossil fuels also releases sulfur dioxide and nitrogen oxides which can cause acid rain. Air pollution can also be caused by tiny particulates from smoke which can cause smog. Some of the world's major cities like Delhi in India and Karachi in Pakistan have dangerously high levels of air pollution.

Land pollution

The rubbish we throw out that is not recycled goes into a land fill. These are huge holes in the ground into which our rubbish is dumped. Some things like batteries cannot be put into landfill sites because of the toxic chemicals they contain. They must be recycled. Other land pollution comes when some people dump rubbish in public or other private places, often to avoid paying for it to be disposed of. This is called fly tipping and is illegal.

Land use

The larger the human population gets, the more land we require. More houses must be built, more resources found, more food must be grown and more waste is produced. This often means less space and fewer resources for other animals and plants.

Biodiversity is significantly reduced when land is cleared for human uses, such as building, quarrying, farming and waste disposal. A reduction in biodiversity occurs when an area of rainforest is cut down to grow crops.

Deforestation

For thousands of years, humans have been deforesting small areas of woodland to build their own houses or grow crops to feed their families. However, in recent years the increase in the human population and development of industrial machinery has meant that much larger areas have been cleared. This is often by large companies who deforest to provide land for cattle, rice fields growing crops for food and biofuels.

curriculum-key-fact
In the last 75 years, over half of the world's rainforests have been cut down. Scientists estimate that 32,000 hectares of rainforest are destroyed each day.

Deforestation destroys the habitats of the organisms that live there and through this kills individuals of many species. Scientists estimate that several hundred species of plant, animal and insect are lost each day partly as a result of deforestation. This means that deforestation is causing extinctions and dramatically reducing biodiversity.

Peat bog destruction

Bogs are very wet areas of land without trees in which many types of moss grow. They are acidic and often have very low levels of nutrients. Here decomposition is very slow and peat is formed from partially decayed plants.

For many years peat was removed from bogs for gardeners to add to their soil or in some countries, to burn as fuel. This dramatically reduced biodiversity. Because peat takes such a long time to form, it is a non-renewable energy resource like fossil fuels.

Peat bogs are a very important store of carbon. We call them carbon sinks. If all the peat was removed and burned this would quickly release a huge volume of carbon dioxide into the atmosphere and contribute to the greenhouse effect.

The greenhouse effect

Without the greenhouse effect, it is estimated that the mean temperature on Earth would be -18°C and there would be very little or no life. So the greenhouse effect itself is a good thing. The greenhouse effect traps some of the energy from the Sun, which keeps our planet at a suitable temperature for life.

The problem is that the increased release of greenhouse gases is causing an increase in the greenhouse effect called the enhanced greenhouse effect.

Carbon dioxide, water vapour and methane are amongst the most common greenhouse gases. Since the start of the Industrial Revolution, in about 1750, the levels of carbon dioxide have increased by 40%.

Global warming

Global warming is the increase in the mean temperature of the Earth. The ten hottest years since records began have been in the last 30 years. The mean increase in the last 100 years has been less than 1°C. This might seem small, but is enough to have devastating consequences on many species in different parts of the world.

Global warming graph showing the percentage of CO2 in the atmosphere since 1700. It remains steady at 0.028 per cent until approx 1850 and then starts rising steeply reaching 0.035 per cent by 2000.Graph showing change in global temperature over 100 year period

As the percentage of carbon dioxide in our atmosphere has increased, so has the Earth's mean temperature.

Note that the shape of the first graph showing the amount of carbon dioxide in the atmosphere is 'exponential' and is a similar shape to graphs showing human population change over the same time period.

When comparing graphs such as changes to carbon dioxide levels and temperature against time, note that the axes are drawn to different scales, and do not start at '0'.

The consequences of global warming and climate change are:

  • melting of the polar ice caps
  • the rise in sea level that will flood many parts of the world and may one day threaten many cities such as London, New York and Amsterdam
  • weather patterns will change with more unusual weather:
    • long-term, in the UK, summers are expected to become hotter and drier, and while plant productivity will increase, some native species of tree in our woodlands may struggle to survive the warmer conditions
  • animals will migrate towards the poles to find habitats with suitable temperatures:
    • in the UK, we are already seeing some species, eg of butterfly, moving northwards, while numbers of some northern species are decreasing because of the warmer conditions
  • tropical diseases may become more common in other regions, such as Europe
  • many species will become extinct