It took 123 years, from 1804 to 1927, for the world population to double from one billion to two billion. Sixty years later, in 1987, the population had hit five billion. It has taken only 12 years to reach six billion in 1999. Much of the rapid population increase can be attributed to better health care, which has reduced infant mortality dramatically and extended life spans. Advanced agricultural techniques allow the same land area to support much larger numbers of people.
People today live longer and healthier lives than any generation in history.
Not everyone sees it that way. Zero Population Growth points out that the impacts of an exploding human population can devastate natural areas and lead to multiple extinctions. Every 20 minutes, the world adds another 3,500 human lives but loses one or more entire species of animal or plant life - at least 27,000 species per year. This is a rate and scale of extinction that has not occurred in 65 million years. Increasing energy use has contributed to global warming, and poor agricultural practices have led to deforestation and desertification.