Earth's population is growing fast. In the year 1700, there were about 600 million people on earth. By 1800, there were about 900 million. In 1900, there were about 1.6 billion. In 2000, there were about 6 billion. That's according to the U.S. Census Bureau.
By the year 2050, there will be about 11 billion people on earth, according to:
http://news.nationalgeographic.com/news/2014/09/140918-population-global...
People are the main cause of climate change, which the world's leading scientists say is a major threat to earth's ability to support human life.