Environment and its functions

The environment is the total of all the biotic (living) and abiotic (non-living) factors around us, which influence each other. Biotic factors include plants, animals, birds and micro-organisms; abiotic factors include air, water, land and sunlight.

The environment does four jobs for us:

• Supplies resources: both renewable and non-renewable.
• Assimilates waste: it absorbs the waste of our production and consumption. Growing wheat gives us grain, but also straw and other waste that nature must break down.
• Sustains life, by providing genetic and biodiversity: the variety of living things.
• Provides aesthetic services: the beauty of mountains, rivers and forests.

The environment can do these jobs only within its carrying capacity. That means two things: we must extract resources more slowly than they regenerate (grow back), and produce waste only as fast as the environment can absorb it (its absorptive capacity). Go beyond these limits, and an environmental crisis follows.

In the past, the demand for environmental resources was less than their supply. Now the population explosion and industrialisation have raised demand beyond supply: a supply-demand reversal.

Two global problems:

• Global warming: the earth's average temperature is rising because of greenhouse gases (such as carbon dioxide), released by burning fossil fuels and by cutting down forests. The Kyoto Protocol (1997) asked countries to cut these gases.
• Ozone depletion: a layer of ozone (O₃) high in the atmosphere protects us from the sun's harmful ultraviolet rays. Chemicals called CFCs (used in old refrigerators and air conditioners) damage this layer. The Montreal Protocol banned them.