Mapping the Globe’s Soils


Scientific American
By Paul Voosen
August 7, 2009

The lack of good information on global soils is hampering efforts to improve agriculture and combat climate change

Long left in the dust by their peers in climate research, a small group of soil scientists is spearheading an effort to apply rigorous computer analysis to the ground beneath our feet.

Their goal: to produce a digital soil map of the entire world.

It is a daunting task. In many parts of the world, such as Africa and South Asia, knowledge of soil is sketchy at best, relying on fading paper maps. And without accurate soil information, it is difficult for planners to know where crops are best grown, or for climate modelers to predict how much carbon might be released from soil into the atmosphere.

"The scientific disciplines are crying for this information," said Alfred Hartemink, the project’s coordinator and a soil scientist at ISRIC, a globally focused soil institute funded by the Dutch government.

Climate scientists, hydrologists, agronomists and ecologists all want to feed these data into their models, Hartemink said, so they can better address big questions: What happens if there’s drought in the Midwest? Or if huge swaths of land are given up for biofuels?

"People are realizing that food comes from the land," Hartemink said. "And if you want to end hunger, then you need to know your soil and the soil needs to be in a good condition."

The project, known as, has received roughly a million dollars in seed money from the Bill and Melinda Gates Foundation. As Hartemink put it, "It’s a map, and [Bill] likes maps. It’s digital, and he likes digital." An offshoot of the effort, the Africa Soil Information Service, has also received $18 million from the foundation.

Soil information is particularly poor in Africa. Indeed, scientists know more about the soils of Mars than Africa, said Pedro Sanchez, a soil scientist and author of a paper published today in Science that describes the team’s work.

"We have the rovers in Mars, and they transmit the spectral signature of soil and rocks," Sanchez said. For instance, "we know the soils of Mars have a lot of salinity." And yet this modern technology has not been applied to large-scale soil surveys in Africa, he added.

The project would largely base its digital map on high-tech extrapolations from existing, pre-digital maps. If successful and funded — scientists estimate the map would cost more than $200 million — the map could provide snapshots of the land over time, in response to changing conditions.

"We assume at the moment that our soils are static, but we know that they’re not," said David Lawrence, a climate modeler based at the National Center for Atmospheric Research.

Plus, reliable global estimates, particularly robust carbon density data, would be welcome, Lawrence said.

"We spend a fair amount of time wondering whether the data we are using is correct," Lawrence said. Often, when models go awry, this is due to incorrect soil data, he added.

Many countries, including the United States, do have accurate legacy maps of their soils, many of which have been scanned into computers. But at low resolutions, these maps have a fatal flaw, scientists say. The land is split into polygons — most maps look like multicolored states after extreme bouts of gerrymandering — and within these polygons, the soil is assumed to be uniform. There is no probability.

As any researcher will tell you, scientists need probability. And so, building from these polygon maps, the project will marshal the statistical force of modern computing and combine it with satellite data obtained over the past decades that reveal plant cover, surface temperature and elevation, as well as existing climate data…

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