The historic rainfall that flooded millions of acres of farmland in the Midwest this spring dealt a blow to an already struggling farm economy.
They also delivered bad news about the climate.
Scientists predict that all that water has pumped massive amounts of fertilizer and manure into waterways, triggering a potentially unprecedented season of algae blooms. The National Oceanic and Atmospheric Administration has predicted that the “dead zone” in the Gulf of Mexico — a massive overgrowth of algae — could become the size of Massachusetts this summer, approaching a record set in 2017, and that an algal bloom in Lake Erie could also arrive record size.
“Everywhere in the Midwest is wet,” said John Downing, aquatic ecologist and director of Minnesota Sea Grant. “There will be an amazing amount of algal blooms.”
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As rain washes nutrients—primarily fertilizers and manure—into streams, rivers, and lakes, those nutrients trigger algae growth, a process known as eutrophication that depletes oxygen in the water. These algae can choke waterways, killing aquatic life and making the water unsafe to swim in or drink.
These algae-filled waterways also emit methane, a powerful climate pollutant. Atmospheric methane has been launched over the past 12 years, threatening global emission reduction targets. Downing and his colleagues have determined that algal blooms could accelerate methane emissions even further.
“Not only are we losing good water,” he said, “we're also exacerbating climate change.”
Rising methane emissions: 'The rates are huge'
On a piece of paper published earlier this yearDowning and his colleagues predicted that as the world's population grows and more nutrients enter waterways over the next century, eutrophication could increase methane emissions from inland waters by 30 to 90 percent.
“We have predicted, based on population growth and food production, how much we can expect eutrophication to affect the climate,” Downing said. “The rates are huge.”
Predictions of increasingly heavy rainfall in the Midwest in the coming decades, along with increased heat, could further drive algal blooms.
“Heavy rainfall causes a lot more runoff, and with climate change, we have warmer temperatures,” said Anne Schechinger, an analyst with the Environmental Working Group. “You have these big rain events and then the heat mixes with these nutrients and causes them to explode in all these bodies of water.”
The group released a map last year which pieces media reports of algal blooms. So far this year, Schechinger noted, he has seen at least 30 algal blooms through early June, including some that never went away during the winter, when they usually subside with cooler temperatures.
Flooding could also mean less fertilizer
The extent of the algae bloom this year depends on the weather. If it is cooler than expected, the blooms may not proliferate as much. The late planting could also mean farmers are using less fertilizer this year.
“It depends on how long the rain continues,” said Bruno Basso, a professor of ecosystem science at Michigan State University. “Not having things on the ground, that's a positive thing, because farmers won't be putting fertilizer on the ground.”
Fertilizer, however, is not the only problem. Environmental groups blame the increase in algae blooms in some areas, particularly around Lake Erie, on the proliferation of concentrated animal feeding operations (CAFOs).
“We found this huge boom in animal businesses starting in the mid-1990s,” Schechinger said. “We think manure is the most important component of what contributes to algae in many of these places.”
Georgina Gustin
Reporter, Washington, DC
Georgina Gustin covers agriculture for Inside Climate News and has reported on the intersections of agriculture, food systems and the environment for much of her journalism career. Her work has won numerous awards, including the John B. Oakes Award for Distinguished Environmental Journalism and the Glenn Cunningham Agricultural Journalist of the Year, which she shared with Inside Climate News colleagues. He has worked as a reporter for The Day in New London, Conn., St. Louis Post-Dispatch and CQ Roll Call, and her stories have appeared in The New York Times, The Washington Post, and National Geographic's The Plate, among others. He is a graduate of the Columbia University Graduate School of Journalism and the University of Colorado at Boulder.
