But tropical environments today are among the most threatened regions. In that case, the unique features of many extinct plants and animals may never have a chance to develop again. We are the sole species in the history of life to have the capacity to cause a mass extinction of many other species. Human activities, including the clearing of forests, the spread of agriculture, the introduction of animals into new environments, and the pollution of air, water, and soil, account for almost all of the extinctions of the last several thousand years. Scientists predict that as the human population grows and human activities increase, the problem will become more serious.
More people require more food and more space to live, and they create more waste.
Since 1950, the world's human population has grown from about 2.5 billion to about 5.7 billion people. In the next 50 years, the number of people is expected to double. Scientists warn that such a population explosion will have a devastating impact on the millions of other species with whom we share the planet. Furthermore, in most developed nations, where population growth is not as rapid, human activities such as agriculture and industry pose an equally serious threat to the world's species. But in addition to acknowledging human beings' capacity to destroy, scientists say we should remember that we are also the sole species to ever have the capacity to save others.