Nearly 70 years ago, a young African-American sprinter named Jesse Owens attracted worldwide attention for his exploits at the 1936 Berlin Olympics, setting three Olympic records and winning four gold medals. For the first time and thanks to the influence of film and radio, his feat reached a global audience and he became a symbol of the power of sport to transcend barriers.

In the years since Owens took the world of athletics by storm, television and the Internet have further revolutionized the way we communicate, and sport has become a business that touches the lives of just about everyone on the planet. Events such as the Olympics or the soccer World Cup are watched around the globe, while companies such as Nike, Reebok and Adidas are household names the world over.

During the same period, the world's human population has nearly tripled and there have been profound changes in the global environment. Climate change, atmospheric pollution, land degradation, water scarcity and the loss of biological diversity are now issues of global importance.

Reversing environmental decline is not just a matter for the world's politicians. It is something that demands action from everyone. That, for example, is why the Olympic Movement has incorporated the environment into its charter, recognizing it as one of the three pillars of Olympism alongside sport and culture.

Many issues link sport and the environment. On the one hand, a degraded environment is detrimental to our health and sporting performance. On the other hand, the multi-billion-dollar global sports industry is a major consumer of natural resources.

It is the cross-cutting, cross-cultural nature of sport that makes it such a potentially important influence for good - or for bad. The way sports events are run, how the sports industry does business, and the manner in which sports stars conduct themselves on and off the field, can have far-reaching effects.

This issue of Tunza features the voices of sportsmen and women who are speaking out in defence of the environment. It also reports practical examples of how sports events, the sports industry and consumers such as ourselves can become more environmentally friendly.

Sport is about the challenge to excel. As Jesse Owens once said, 'the only victory that counts is the one over yourself'. The goal is always to improve one's own performance. The challenge for our generation is to improve on our performance as stewards of this planet, our one and only home, so that children growing up 70 years from now can enjoy their sport in a clean, safe environment.

ART BY DEIA SCHLOSBERG/PCI