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| Atmospheric ozone depletion is one of the most dramatic examples of how human economic activities began destroying a life supporting ecosystem, and did so over a relatively short period of time – just a few decades. The ozone layer in the upper stratosphere covers the globe and protects all terrestrial life forms from solar Ultraviolet (UV) radiation. Without this thin protective layer over the globe, these UV rays would make life on the surface of the earth virtually impossible. Indeed, life did not emerge on the earth’s surface until after this protective ozone layer formed hundreds of millions of years ago. |  |
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| In the 1930’s ozone depleting chemicals (ODCs) were developed for commercial use, largely in aerosol applications and for refrigeration. CFCs (chloro-fluoro-carbons) were the most common of these ODCs, and their production increased dramatically as refrigeration technologies spread across the globe over the next several decades. In 1974 a scientific paper was published which raised concerns about the impact of CFCs on atmospheric ozone. Predictably, the industries using these chemicals denied the validity of these theories and did what they could to discredit the scientists who were sounding the alarm. This allowed political decision makers to also ignore the scientists – at least for a while. |  |
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| The rapid increase in ODC production led to a thinning of atmospheric ozone, largely over the poles, and hardly at all in the tropics. By 2000 thinning was most pronounced at the poles, and a hole roughly the size of continental United States appears over Antarctica under certain climatic conditions. While the ozone holes over the poles have received the most media attention, it should be noted that significant thinning also has occurred over the northern and southern temperate zones, where most of the human population lives. A variety of negative human,animal and plant health impacts have already been noted. Unchecked, the continued production and use of ODCs would have significantly altered life on earth. |  |
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| Fortunately, the scientists involved, along with various civil society organizations and ordinary citizens, eventually convinced the relevant governments to take action. Through a series of international agreements the production of various ODCs has been banned, limiting the further destruction of the ozone layer. Refinements to these international agreements are ongoing, as new ODCs are identified, and issues such as smuggling of ODCs are discovered. |
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| Despite the successes of these international agreements, the protection provided by the ozone layer will not return to its pre-ODC levels until the 22nd century. This delay in returning to its former level is due to the long-acting effect of many ODCs. CFCs, for example, once they enter the stratosphere, remain active for approximately 100 years. In the meantime, increased human health impacts, as well as negative impacts on a variety of plant and animal species will continue. |
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| The apparent success of the international treaties regulating ODCs seems to have at least slowed the damage done to the protective ozone layer. By the standards of geopolitics, these treaties occurred relatively quickly, despite initial objections from the industries involved. Nonetheless, hundreds of thousands of additional cases of skin cancer, cataracts and human immune suppression occurred over the short time it took to recognize and respond to the problem. |
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| Despite the success of international treaties reducing the production of ODCs, there are important questions that remain unanswered. We do not know if some irrevocable damage to a critical life supporting ecosystem service has already occurred, but not yet been identified. Nor do we know if ongoing ozone depletion will cause irrevocable damage in the future. Nor do we know how the ongoing depletion will impact other areas of concern, such as climate change. |
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