Ozone is a form of oxygen. In the stratosphere, around 25 km above the Earth’s surface, there is a layer of ozone that absorbs ultra-violet light from the Sun. Ultra-violet light is known to cause skin cancer in humans, and to damage plants. The ozone layer forms a protective shield around the Earth, and without it most life on Earth would not be likely to survive.
In the 1970s scientists realised that a hole was appearing in the ozone layer over Antarctica during the spring. They realised that this was due to the build-up of chlorofluorocarbons (CFCs) – chemicals used in aerosol sprays, packaging and air conditioning systems. One molecule of CFC can remove up to 100,000 ozone molecules, and the widespread use of CFCs before the damage was noticed has produced a serious problem. Life on the planet will not be sustainable if the ozone layer is destroyed, because damage caused to plants will severely reduce the global food supply.
International action has been taken to relieve the problem. In 1987 the Montreal Protocol was agreed which requires countries to take steps to eliminate CFCs and other substances which cause ozone depletion. If CFC levels are reduced considerably, particularly in the developing world, then the ozone layer will probably fully repair itself by around 2050. Agenda 21 suggests that the ozone layer can be viewed as a vital resource for life, and should be protected for sustainable development to be achieved.