US scientists find way to measure small-farm crop yields from space

LONDON • Researchers in the United States have come up with a new method of estimating crop yields from small farms in Africa using high-resolution images from the latest generation of satellites - a development which could help cut hunger in poor parts of the world.

Improving agricultural productivity is one of the main ways to lift people out of poverty, but without accurate data it is difficult to identify the farmers who need help, scientists from Stanford University said.

Images from new, inexpensive satellites could be used to estimate yields and test interventions in poor regions where data is scarce, they said in a paper published in the Proceedings Of The National Academy Of Sciences on Monday.

"Improving agricultural productivity is going to be one of the main ways to reduce hunger and improve livelihoods in poor parts of the world," said Dr Marshall Burke, an assistant professor at Stanford's School of Earth, Energy and Environmental Sciences. "But to improve agricultural productivity, we first have to measure it and, unfortunately, this isn't done on most farms around the world," he said.

While Earth-observing satellites have been around for more than three decades, most of their images have not been detailed enough to show the small agricultural fields common in developing countries.

But with satellites becoming cheaper and offering improved image resolution, it is now possible to capture very small areas, the researchers said.

Dr David Lobell, an associate professor at the school, said in a video that satellites which were once the size of school buses were now the size of fridges or even shoeboxes.

"You can get lots of them up there, all capturing very small parts of the land surface at very high resolution," added Dr Lobell, who co-authored the study. "Any one satellite doesn't give you very much information, but the constellation of them actually means that you're covering most of the world at very high resolution and at very low cost. "

The researchers focused on western Kenya, where smallholders farm maize or corn on small 0.2ha or 0.4ha plots, to test if images from the new satellites were detailed enough to provide reliable estimates of crop yields. "Just combining the imagery with computer-based crop models allows us to make surprisingly accurate predictions," Dr Burke said.

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A version of this article appeared in the print edition of The Straits Times on February 16, 2017, with the headline 'US scientists find way to measure small-farm crop yields from space'. Print Edition | Subscribe