News Section
Stories from Climate Central's Science Journalists and Content Partners

Warming May Mean More Toxic Algae Blooms for Lake Erie

Toxic algae blooms in Lake Erie could come more often and be more intense in coming decades thanks in part to torrential rains intensified by global warming, according to a study published in Monday’s Proceedings of the National Academy of Sciences.

Heavy runoff from farmland, say the authors, can carry nutrient-rich fertilizer into the western part of the lake, triggering a population explosion of blue-green algae that pump poisons while they live and can rob the water of oxygen when they die and decompose.

Aerial shot of a Lake Erie algae bloom.
Click Image to enlarge. Credit: NOAA.

And according to the study, if farming practices stay the same, the millions of people who depend on Lake Erie for drinking water and recreation — and by extension, those who depend on the other Great Lakes as well — could see water quality degrade significantly.

The report’s assertion isn’t just theoretical. In 2011, an enormous algae bloom struck Lake Erie, spreading to cover about 2,000 square miles — a record, and some three times more than the biggest of the algae blooms that grabbed headlines in the 1960s and 1970s. 

“Lake Erie was famously declared dead at the time,” said co-author Don Scavia, an environmental engineer at the University of Michigan, in an interview. But in the  following decades, strict controls on sewage treatment plants reduced pollution and allowed the lake to recover.

Then came torrential rains in May, 2011, including a storm that dumped 2 inches of water on the region in 24 hours. Fertilizer from thousands of square miles of corn, soybean and wheat fields was flushed into the lake, and algae literally ate it up.

The rains alone wouldn’t have caused such a problem, Scavia said, but starting in the 1990s, several changes in farming practices left more fertilizer on top of the ground. One was the increasing application of fertilizer in the fall, where it would sit on the frozen fields through winter, ready to go to work as soon as crops began sprouting in spring.  Another was an increase on the acreage devoted to corn, a fertilizer-intensive crop — especially over the past few years as the federal government encouraged the use of corn ethanol to replace gasoline.

Blue green algae bloom on the shore of Catawaba Island, Ohio in Lake Erie. Summer 2009.
Click Image to enlarge. Credit: NOAA Great Lakes Environmental Research Laboratory/ flickr.

Yet another factor was a movement toward no-till agriculture, which eliminates annual plowing. “The irony is that this change was driven by valid environmental concerns,” said lead author Anna Michalak, a statistician with the Carnegie Institution for Science, in Stanford, Calif., in an interview. Old-fashion plowing is being phased out because it loosens the soil and promotes erosion; it also churns up nitrogen and carbon, putting extra heat-trapping greenhouse gases into the atmosphere. But if fertilizer is spread on top of the ground rather than being plowed under, it’s also easier to wash away in a heavy downpour.

Such downpours are expected to come more often as the world warns: a warmer atmosphere can hold more water vapor, but it also has more to dump during rainstorms. In fact, scientists have already seen both dry spells and heavy rains increase across the globe, and climate models generally agree that this so-called hydrological cycle will continue to become more extreme. “If you combine the changes in farming with the changes in frequency and intensity of severe rains, we think those things are conspiring to make algae blooms worse,” Scavia said.

In fact, the scientists did simulations to test this hypothesis. “We took 1970s weather combined with the agricultural practices of the 2000s, and 2000s weather with 1970s agriculture,” Scavia said. In both cases, the amount of fertilizer entering Lake Erie was significantly lower. When the team ran climate-model simulations of future precipitation in the area, said University of Michigan climatologist Allison Steiner, another co-author, in an interview, “we saw an increase both in intense and very intense rain events.” 

The biggest lesson, however, has to do with the danger of looking at just one aspect of how climate change might affect a specific part of the world. Increased rainfall alone didn’t cause the 2011 algae bloom, Michalak said, and adapting to climate change will require scientists and policymakers to look beyond just what’s happening to the climate.

“It speaks to the need to look at the environment as a very complex, interrelated system,” Michalak said. 

Related Content
Report Details Climate Change, Extreme Weather Links
Climate Change Has Intensified the Global Water Cycle
Changes in Sea Saltiness Show We're Affecting the Climate
Heavy Midwestern Rains Lead to Mississippi Floods

Comments

By Dave (Basking Ridge, NJ 07920)
on April 2nd, 2013

Blue green algae seem to be everywhere.  Feed them intensively and of course they will grow, reproduce, use up the oxygen to the detriment of other fish etc and produce dead zones. But normally, they are an important part of our environment. You can’t really blame farmers either for using fertilizer or ask them to use less. I doubt that farmers spend more on fertilizer than they feel they need to. Maybe part of the answer lies on the demand side. For instance, do we really need corn ethanol?  The environmental rationale for that has been debated back and forth for some time. I’m not sure where that debate stands today but these kinds of significant ripple through impacts should clearly also be taken into consideration. This general dead zone / run off issue keeps coming up and factors into impacts on fisheries, coral reefs, tourism and so on. The big dead zone in the Gulf of Mexico, due to run off carried by the Mississippi River, can be huge.

Reply to this comment

By Isabella (Athens, Ohio 45701)
on April 2nd, 2013

The effects of climate change seem to be endless. Climate change effects us all in many ways in all areas. As a Cleveland native, algae blooms in Lake Erie are nothing new. There are so many entries to the waterways of Lake Erie that it is so simple for agricultural runoff to pollute the great lake. I remember not being allowed into certain parts of the lake because of contamination and intense algae blooms. Recreational parts of the water are now being closed because of this. In 2011, a huge algae bloom hit Lake Erie that spread to cover 2,000 square miles. Torrential rains due to the warming climate certainly don’t help stop the contamination. A warmer climate means a warmer atmosphere that can hold more water vapor which means more and intense dumping of water during a rainstorm. With the areas laws against plowing (no till agriculture) it is way easier for fertilizer to runoff into Lake Erie. A lot of North East Ohioans depend on Lake Erie. What happens when we cant anymore?

Reply to this comment

By Vickie Askins (Cygnet, Ohio 43413)
on May 26th, 2013

There is one relatively new farming practice that is getting very little attention - and that would be the influx of Concentrated Animal Feeding Operations in the Lake Erie Western Basin watershed.  Although the Phosphorus Task Force reported commercial fertilizer sales had decreased dramatically over the past 20 years, draft legislation would force row-crop farmers to restrict commercial fertilizer applications.  Ironically, the Ohio EPA has conceded - “Effective MANURE management is critical if we are to see water quality improvements and/or measurable reductions in nutrient loadings to our streams.”

The Ohio Department of Agriculture is supposed to regulate industrial animal operations.  However, the ODA claims land application of massive amounts of manure produced by these huge animal factories would be outside Clean Water Act obligations if it’s spread by untrained farmers instead of ODA-trained brokers – a.k.a. the “manure loophole”.
The ODA recently approved permits for a new 4.1 million poultry facility in the Maumee River watershed – which empties into Lake Erie’s western basin.  This operation will utilize the manure loophole for over 63,000 tons of solid manure it will generate annually.  Shortly, the ODA will also approve a permit for a new 5,000-head sow finishing factory farm near Wauseon.  This operation will produce over 2 million gallons of waste each year which will also be applied to fields in the Western Basin.
Why is the ODNR spending millions of taxpayer dollars to restrict commercial fertilizer while the ODA is giving manure fertilizer a free pass?  In light of excessive nutrients flowing down the Maumee River into Lake Erie, why doesn’t Ohio designate the Lake Erie watershed as a WATERSHED IN DISTRESS in order to restrict all unsafe farming practices?
Everyone should be outraged the ODA allows factory farms to use a deceptive loophole which could jeopardize the future of Lake Erie! 

Reply to this comment

Name (required):
Email (required):
City/State/Zip:
Enter the word "climate" in the box below:

[+] View our comment guidelines.

Please note: Comment moderation is enabled. Your comment will not appear until reviewed by Climate Central staff. Thank you for your patience.