You should expect more than ghosts, spirits and candy when Halloween arrives this year. On October 31, 2011, the world will welcome its seven billionth person, according to the United Nations Population Fund.
Reaching such a large global population would have fascinated 19th century theorist Thomas Malthus. According to the Financial Times, Malthus argued -- at a time when the world's population was under 1 billion -- the birth rate had to be lowered to prevent the famine and violence that would come with overpopulation.
Human ingenuity and technology have played a big part in defying Malthus, but there's no doubt the population explosion has taken a toll on the earth's resources. As Treehugger reported, the population spike since the 18th century has contributed a whole slew of environmental issues, including soil erosion and dwindling wild fish populations.
The Center for Biological Diversity has launched an advocacy campaign pegged to the 7 billion mark to highlight overpopulation and its impact on endangered plants and animals. As part of the "7 Billion and Counting" campaign, the center is giving out 100,000 endangered species condoms to a network of 1,200 volunteer distributors in all 50 states.