Reaping What We Sow: Mapping the Urbanization of Farmland Using Satellites and City Lights

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Part two of a three part series.
Part 1: Bright Lights, Big City
Part 3: Urbanization’s Aftermath

When most animals in the wild multiply to the point where they require more food than is available in their habitat, they eat what they can and then starve in droves. From dinosaurs to present-day deer populations, this basic rule of nature has held fast for nearly every animal species with one notable exception—us. Many anthropologists believe that 10,000 years ago, when the human population reached its natural limit of 10 million people (Imhoff et al., 2000), the agricultural revolution began so that the hunter-gatherers could ensure their survival. Ever since, we humans have been growing in number, precariously and diligently avoiding what seems to be a Malthusian fate by engineering new ways of reviving our soil, changing the flow of the Earth’s water, and even genetically altering our crops.

Now that the number of people on the planet has surpassed the six billion mark, it is more important than ever that we actively protect our natural resources. Yet, many researchers fear we may be doing the exact opposite. As our population continues to swell, our self-made urban and suburban habitats have begun to consume enormous tracts of once rural landscape. What is worse, some researchers believe, a majority of this landscape is prime farmland.

Tracking this phenomenon, however, has always been difficult. Urbanization moves relatively fast and its outlines are often hard to discern. Recently, a group of researchers at Goddard Space Flight Center, led by climatologist and remote sensing specialist Marc Imhoff, came across a solution. Using satellite images of city lights at night, they constructed a map of the urbanized areas of the United States and several other countries. They then integrated this map with a soil map that the United Nations prepared. These NASA researchers found that while the residents of these countries are not going to starve tomorrow, they may indeed be destroying their best soils and putting future generations at risk.

Biting the Hand that Feeds Us

The data used in this study are available in one or more of NASA's Earth Science Data Centers.

Farms
Scenes like this—rolling farmland punctuated by isolated farmhouses—are becoming increasingly rare as cities and suburbs expand into rural land. (Photograph courtesy USDA Photography Center)

Chicago at Night
The above photo of the lights of Chicago was taken by an astronaut aboard the space shuttle. The bright lights of the city center are bounded by the black waters of Lake Michigan on the right, and they fade into dark rural landscapes on the left. Scientists assembled a dataset of lights detected from space to measure the extent of cities and urban areas worldwide. (Image courtesy NASA, Photo ID STS081-376-1)

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