John R. Wilmoth, director of the United Nations Population Division predicted the world’s population would reach 11.3 billion people by the end of the 21st century in a speech at Seattle’s annual Joint Statistical Meeting Monday.

An article in csmonitor.com reports the body is predicting the Earth’s population to be between 9.5 and 13.3 billion people by the year 2100.  Previous predictions have said the world population would peak out at around 9 billion by 2050.  The report also said there was about a 23 percent chance the population growth would stop within the next 100 years.

The primary reason for the increase is expected rapid growth in sub-Saharan Africa.  Some of these areas that have an exceedingly high population growth will continue to grow unless there is a decline in the fertility rate.  The continent has about 1.2 billion people today, but that number is expected to rise to somewhere between 3.4 and 5.6 billion by 2100.

Some of the poorest nations on Earth live in the region, and as these areas are becoming more developed, the strain on energy demands will harm the local economies, that are ill-equipped and under funded.  These areas are not likely to adapt effectively to changing climate and increased populations.

As the world approaches Earth Overshoot Day, as defined by the sustainability think tank Global Footprint Network, the rapid increase in population growth is receiving heightened focus.  Earth Overshoot Day is the day when the Earth’s population uses more natural resources than the world can generate in a year.  This will lead to a depletion of natural capital and add additional carbon dioxide in the air.

The Global Footprint Network estimates the current rate of using natural resources is requiring 1.6 Earths to be sustainable, based on today’s population.

The United States population, currently at 322 million, is expected to hit 450 million by 2100.