"We’re living at a very special point in human history with respect to population growth," says Imhoff. "We’re adding whole country-sized populations of people in decreasing time intervals." The human race reached one billion people in 1818. Since then it has been growing geometrically, reaching two billion by 1932, four billion by 1982 and close to six billion by 2000. Though the growth rate is slowing down now, the Earth is expected to house 10 billion people by the year 2050.
 

On the whole, Imhoff explains that the human population now consumes and burns as much as 40 percent of all new plant growth on the Earth every year (Imhoff et al., 2000). Most of the best soils in the world have already been cultivated in one fashion or another to grow everything from asparagus to cotton to pine trees to wheat. As the human population expands, it is likely that we will have to keep all the farmland we have as well as cultivate much of the remaining arable land on Earth.

We may, however, be sabotaging ourselves. Along with staggering population growth over the last century has come a mass movement towards the cities. Worldwide, human flight towards large urban areas is boosting the urban population upward three times faster than the general population growth. Only a third of the planet’s population lived in urban areas ten years ago. Now it’s up to 50 percent and in ten more years it will be up to two thirds. This mass movement to the cities has caused urban areas to expand at an enormous rate. In the United States alone, 19,000 square miles of otherwise rural cropland and wilderness were developed between 1982 and 1992 (World Resources Institute, 1996).
 

The problem with all this urban development has to do with where most major cities around the world are located. "Because we are biological entities, we follow biological resources," Imhoff says. He explains that in the past, people laid down the foundations of our modern day metropolises in areas where the land was flat, the water and soil were good and the climate was temperate. These are the same regions that make for good farmland. Though urban sprawl today normally only covers two to five percent of the total land in any given country, that very land may be our most arable. And once an area of land is urbanized, it is very difficult to bring the soil back to its former state.

 The Aura of Urbanization
 Reaping What We Sow