The human population grew from 1.6 billion to 6.1 billion people during the course of the 20th century. That means it took more than 8,000 years to reach 1.6 billion and just the last 100 years to increase that number by 4.5 billion! Over 250,000 people are added every day.
Today, humanity consumes the equivalent of 1.3 planets to provide the resources we use and to absorb the waste we create. And if all nations consumed natural resources at the same rate as America, we would need six Earths to survive.
Source: United Nations Population Fund; World Bank; U.S. Census Bureau