Cleaner air has boosted US corn and soybean yields

Date:
July 1, 2021
Source:
Stanford University
Summary:
The analysis estimates pollution reductions between 1999 and 2019
contributed to about 20 percent of the increase in corn and soybean
yield gains during that period - an amount worth about $5 billion
per year.



FULL STORY ==========================================================================
A key factor in America's prodigious agricultural output turns out to be something farmers can do little to control: clean air. A new Stanford-led
study estimates pollution reductions between 1999 and 2019 contributed to
about 20 percent of the increase in corn and soybean yield gains during
that period - - an amount worth about $5 billion per year.


==========================================================================
The analysis, published this week in Environmental Research Letters,
reveals that four key air pollutants are particularly damaging to
crops, and accounted for an average loss of about 5 percent of corn
and soybean production over the study period. The findings could help
inform technology and policy changes to benefit American agriculture,
and underscore the value of reducing air pollution in other parts of
the world.

"Air pollution impacts have been hard to measure in the past, because
two farmers even just 10 miles apart can be facing very different air
quality. By using satellites, we were able to measure very fine scale
patterns and unpack the role of different pollutants," said study lead
author David Lobell, the Gloria and Richard Kushel Director of the Center
on Food Security and the Environment.

The research highlights the considerable power of satellites to illuminate pollution impacts at a scale not possible otherwise. That power could
be of even greater value in countries with less access to air monitors
and yield data.

Reading the air Scientists have long known that air pollution is toxic to
plant life in high doses, but not how much farmers' yields are actually
hurt at current levels.

The impact of pollution on agriculture overall, as well as the effects
of individual pollutants, has also remained unknown.



========================================================================== Focusing on a nine-state region (Illinois, Indiana, Iowa, Michigan,
Minnesota, Missouri, Ohio, South Dakota and Wisconsin) that produces
roughly two-thirds of national maize and soybean output, Lobell and
study co-author Jennifer Burney, an associate professor of environmental science at the University of California, San Diego, set out to measure
the impact on crop yields of ozone, particulate matter, nitrogen dioxide
and sulfur dioxide.

Ozone is the result of heat and sunlight-driven chemical reactions between nitrogen and hydrocarbons, such as those found in car exhaust. Particulate matter refers to large particles of dust, dirt, soot or smoke. Nitrogen
dioxide and sulfur dioxide are gases released into the atmosphere
primarily through the burning of fossil fuels at power plants and other industrial facilities.

"This has been a tricky problem to untangle because historically our measurements of different types of air pollutants and our measurements of agricultural yields haven't really overlapped spatially at the necessary resolution," explained Burney. "With the new high spatial resolution
data, we could look at crop yields near both pollution monitors and
known pollutant emissions sources. That revealed evidence of different magnitudes of negative impacts caused by different pollutants."
Lobell and Burney extended their analysis back to 1990, when Congress
passed Clean Air Act amendments that resulted in significant air quality improvements across the country. The researchers looked through air
pollution data from hundreds of monitoring stations around the region,
federal data on power plant emissions, satellite-based observations of
nitrogen dioxide around those power plants, crop yield data from federal surveys and satellite imagery, as well as weather data to account for
growing season conditions known to explain crop yield variations.

Surprising findings What Lobell and Burney discovered surprised
them. Among their findings: negative effects of each of the four
pollutants on corn and soybean yields, and a clear yield increase the
farther away from power plants -- particularly coal- burning facilities -- crops were grown. The unique spatial patterns of each pollutant allowed
them to disentangle the effect of each pollutant in a way that past
studies could not.

The researchers estimated that total yield losses from the four pollutants averaged 5.8 percent for maize and 3.8 percent for soybean over the past
two decades. Those losses declined over time as the air grew cleaner. In
fact, the reduction in air pollution contributed to an estimated 4
percent growth in corn yields and 3 percent growth in soybean yields -- increases that equal 19 percent of corn's overall yield gains during
the timeframe and 23 percent of soybeans' overall yield gains.

"We already know that the Clean Air Act resulted in trillions of dollars
of benefits in terms of human health, so I think of these billions in agricultural benefits as icing on the cake," Lobell said. "But even if
it's a small part of the benefits of clear air, it has been a pretty big
part of our ability to continue pushing agricultural productivity higher."
This research was funded by NASA and the National Science Foundation.

========================================================================== Story Source: Materials provided by Stanford_University. Original written
by Rob Jordan.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. David B Lobell, Jennifer A Burney. Cleaner air has contributed
one-fifth
of U.S. maize and soybean yield gains since 1999. Environmental
Research Letters, 2021; DOI: 10.1088/1748-9326/ac0fa4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210701195259.htm

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