Why Industrial Farming and Climate Change Mean More Toxic Drinking Water for the Midwest

Scientists call for cuts in the use of agricultural fertilizers to prevent runoff from contaminating water supplies.

(Photo: Joshua Lott/Reuters)

Aug 7, 2014· 2 MIN READ
Hannah Hoag reports on the environment, global health, science, and science policy for Nature, Discover, Wired, and others.

The toxic Lake Erie algae bloom that contaminated the drinking water of half a million people in Ohio last weekend was no fluke, scientists warn.

The primary culprit behind the algae bloom is spring fertilizer runoff from agricultural fields flowing into the Maumee River, which empties into Lake Erie. Fertilizer contains phosphorous, an element that fuels the growth of blue-green algae. The algae in turn produce the toxin microcystin.

Heavy rains in the late spring wash phosphorous into Lake Erie when the waters are warm and the winds are calm—the perfect conditions for blue-green algae growth. Lake Erie is the most shallow and warm of the Great Lakes. It is also the most susceptible to the effects of climate change, according to scientists, and to “eutrophication.” That’s an abundance of nutrients in the water that trigger algae growth and fish kills from oxygen deprivation.

Scientists say there is evidence that those spring rains have grown more intense over the past decade or so as the planet has warmed, sending more phosphorous into the lake.

“It’s difficult to say if these are long-term changes,” said Rick Stumpf, an oceanographer at the National Oceanic and Atmospheric Administration, who works on forecasts of harmful algae blooms. “But in the last several years we have had wetter springs in general than in the previous six years.”

The National Climate Assessment, released earlier this year, predicts that with continued greenhouse gas emissions, heavy rainfall events will become four times more common along Lake Erie’s shore by 2100. “It would tend to suggest that we might have more runoff in the future,” said Stumpf.

So what can be done?

The answer is simple. “Reduce the phosphorous load, and we can reduce the blooms,” said Stumpf.

That means changing industrial farming practices that have turned a vast swath of the Midwest into corn and soybean fields fertilized with huge amounts of phosphorous. Not so easy.

In February, the International Joint Commission, a United States–Canadian group that monitors the health of the Great Lakes and other shared waters, issued a report calling for cuts to the amount of phosphorous flowing into Lake Erie.

“If you want immediate results and significant impacts, you have to reduce those loadings by 40 percent,” said Raj Bejankiwar, a scientist at IJC and lead author of the report.

The report also pressed Ohio, Michigan, Indiana, Pennsylvania, New York, and Ontario to ban the application of manure, biosolids, and commercial fertilizers containing phosphorous on frozen or snow-covered grounds that drain to Lake Erie.

“We need a quick and aggressive action,” said Bejankiwar.

Lake Erie has been hit with big algae blooms six out of the past seven years. In 2011, an algae bloom covered 1,900 square miles of the lake—one-sixth of its surface. In early July, NOAA scientists predicted this year’s bloom would be the fourth worst in more than a decade.

It’s not over yet. Bejankiwar said the bloom could continue into the fall. Besides contaminating drinking water, algae can create low-oxygen dead zones that kill fish and other aquatic life.

Algae blooms nearly killed off Lake Erie in the 1960s and ’70s, leaving beaches empty and tainting municipal water supplies. Unregulated dumping of sewage and industrial pollutants, leaky septic tanks, and runoff from fertilized lawns and farms supplied the phosphorous the algae need to grow.

The federal Clean Water Act and government programs in Canada and the U.S. helped upgrade sewers and sewage treatment and removed phosphates from household detergents. That halved the phosphorous entering Lake Erie, and algae blooms subsequently subsided.

But in the mid-1990s, the blooms began to reappear, steadily increasing in severity. In 2011, more than half the phosphorous came from tributaries that feed into Lake Erie and drain large agricultural areas.

“This is a wake-up call,” said Bejankiwar of last weekend’s toxic water crisis in Ohio. “It’s time for action.”