"I don't claim to have any special interest in natural history, but as a boy I was made aware of the annual fluctuations in the number of game animals and the need to adjust the "cull" to the size of the surplus population. It took about three and a half billion years for life on earth to reach the state of complexity and diversity that our ancestors knew as recently as 200 years ago. It has only taken industrial and scientific man those 200 years to put at risk the whole of the world's natural system. It has been estimated that by the year 2000, some 300,000 species of plants and animals will have become extinct, and that the natural economy, upon which all life depends, will have been seriously disrupted. The paradox is that this will have been achieved with the best possible intentions. The human population must be properly fed, human life must be preserved and human existence must be made safer and more comfortable. All these things are obviously highly desirable, but if their achievement means putting the survival of future generations at risk, then there is a pressing obligation on present generations to apply some measure of self-restraint. What has been described as the «balance of nature» is simply nature's system of self-limitation. Fertility and breeding success create the surpluses after allowing for the replacement of the losses. Predation, climatic variation, disease, starvation--and in the case of the inappropriately named Homo sapiens, wars and terrorism--are the principal means by which population numbers are kept under some sort of control. Viewed dispassionately, it must be obvious that the world's human population has grown to such a size that it is threatening its own habitat; and it has already succeeded in causing the extinction of large numbers of wild plant and animal species. Some have simply been killed off. Others have quietly disappeared, as their habitats have been taken over or disturbed by human activities."