The efforts to heal the hole in the ozone layer form one of the few environmental success stories. This hole developed primarily due to human activity, particularly the use of CFCs. These chemicals have now been banned by most countries and it has been predicted that the ozone hole will begin to heal in a few years.
The term ozone layer refers to the ozone in the stratosphere. The stratosphere is a layer in the atmosphere at an altitude of 10-50 km which has a relatively high concentration of ozone in it. The ozone in this layer plays a crucial role by absorbing most of the ultraviolet (UV) radiation coming from the sun. UV radiation can be very destructive to life, including ourselves. The depletion of the ozone layer has been associated with, among other things, a rise in skin cancer.
In the late seventies scientists noticed that the ozone layer was thinning due to large scale release of manmade pollutants, in particular chlorofluorocarbons (CFCs). While catalysts that break down ozone occur naturally and are often produced by volcanic activity this is a small percentage of those released by human activity.
Perhaps surprisingly, efforts were made early on to halt the damage being caused to the ozone layer. In 1978 three countries, the United States, Norway and Canada banned CFCs from use in aerosols.
After the discovery of the enormous hole over Antarctica in1985, things went further with an international treaty. The Montreal Protocol was an agreement to reduce, and finally phase out, the use of ozone damaging CFCs. It wasn’t however until 1996 that the phase-out was complete, and some countries never signed up to it in the first place.
It seems to have been enough though. In the last decade the depletion of the ozone layer has slowed dramatically. Scientists predict that it will start to recover in the next decade, although it could take up to a hundred years for the ozone layer to heal completely.
It might be worth noting that at the same time as governments were taking action there was growing public awareness of the environment. Consumers were taking steps themselves by not buying products containing CFCs. Green consumerism helps solve environmental problems, although it probably is not enough by itself in most cases.
The story of the ozone hole reveals that environmental damage is not always irreversible. There might be a lesson to be learnt as we decide how to deal with the other environmental crises we have caused.