The human population
Humans are probably the most adaptable of all organisms. In the last 150 years the human population on Earth has increased from about 1000 million to about 6000 million.

Increases in the human population has resulted in:

• an increased demand for food, materials and energy resources;
• an increased destruction of habitats for industry, farming, houses and roads;
• an increased need to dispose of waste.

Each of these increases is creating problems for the future survival of many living things, including humans. Many people believe that the only way to avoid disaster is to introduce reliable methods of birth control throughout
the world.

Pollution
In some highly populated areas, the activities of humans are leading to serious pollution problems.

• Air pollution is caused by the release of poisonous gases. These include carbon dioxide, carbon monoxide, sulphur dioxide and nitrogen oxides.
  Most air pollution is caused by burning fossil fuels in our homes, in power stations and in our vehicles.
• Pollution of the air from the burning of fossil fuels has led to:
  - acid rain mainly from sulphur dioxide and nitrogen oxides;
  - the 'greenhouse effect' mainly from carbon dioxide trapping heat in the Earth's atmosphere;
  - global warming due to an increase in average temperatures throughout the world.
• Water pollution has affected our rivers, lakes and oceans. The main water pollutants are sewage, oil, fertilisers and pesticides.

Conservation of wildlife and habitats
In some parts of the world, our effects on wildlife and habitats have been disastrous. In the future, it is crucially important that we protect endangered species and preserve habitats.

There are already some successful conservation projects throughout the world. These include:

• Regulations to reduce air pollution and water pollution.
• Reclaiming areas damaged by mining and industry.
• Improved management of habitats, nature reserves and national parks.
• Restrictions on the number of wild animals taken for food.