2012: World population reaches 7 billion

According to the U.S. Census Bureau, world population will reach 7 billion during the middle of 2012. By 2025, we will cross the 8 billion mark. The rate of population growth has decreased to 1.2 percent, down from 2 percent in the 1960s, but world population is still growing at an exponential rate.

Why does this matter? The majority of the population growth will occur in the developing world in countries least able to handle it. A recent report released by the National Petroleum Council states that by 2020, the population of the world's 100 largest cities will grow by 191 million, and 90% of that growth will be in developing world.