The Midwest boasts more photosynthetic activity than any other spot on earth, NASA and university scientists have discovered as part of a project studying data from satellite sensors.
Activity is measured by the magnitude of glow that healthy plants converting light to energy via photosynthesis emit. It's also produced by chlorophyll, which also emits a fraction of absorbed light as fluorescent glow.
Research in 2013 led by Joanna Joiner, of NASA's Goddard Space Flight Center in Greenbelt, Md., demonstrated that fluorescence from plants could be teased out of data from existing satellites, which were designed and built for other purposes.
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The new research, led by Luis Guanter of the Freie Universität Berlin, used the data for the first time to estimate photosynthesis from agriculture. Results were published on Ag Day, March 25, in the Proceedings of the National Academy of Sciences.
According to co-author Christian Frankenberg of NASA's Jet Propulsion Laboratory in Pasadena, Calif., the paper shows that fluorescence is a much better proxy for agricultural productivity than anything that's been used before.
"This can go a long way regarding monitoring – and maybe even predicting – regional crop yields," he says.
Expanded uses for satellites
The whole project was launched in 2012 to explore measurements of photosynthesis from space. The team noticed that on an annual basis, the tropics are the most productive – but during the Northern Hemisphere's growing season, the U.S. Corn Belt "really stands out," Frankenberg said.
"Areas all over the world are not as productive as this area," he notes.
The researchers set out to describe the phenomenon observed by interpreting the data from the Global Ozone Monitoring Experiment 2 on a European meteorological satellite.
Data showed that fluorescence from the Corn Belt, which extends from Ohio to Nebraska and Kansas, peaks in July at levels 40% greater than those observed in the Amazon.
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