From the 1960s to the 1980s, said Glenn Benoy, a senior water quality specialist and science adviser with the International Joint Commission. the main source of phosphorus was sewage plants. The algae problem was considered so serious that communities on the shores of the lake poured billions of dollars into sewage infrastructure upgrades and implemented laws banning phosphorus in laundry detergents.
This time the main problems are thought to be ones that governments have much less direct control over. To some extent, they include the application of fertilizers to lawns and golf courses, growing expanses of pavement in urban areas that cause water to drain more quickly into waterways without being filtered by vegetation, and invasive zebra mussels that release extra nutrients into the water as they feed. But those aren't thought to be the biggest cause.
"We think farming is the major culprit behind the current levels of phosphorus that's in runoff and the phosphorus loads that are getting dumped into the western basin of Lake Erie," Benoy told CBC News.
The commission's report suggested that changes to farming practices were largely to blame for recent blooms.
"The main changes that are responsible have to do with intensification of farming – getting more out of the land than we did historically," Benoy said, adding that that includes things like:
- More livestock farming and greater application of their waste to fields.
- Higher application of fertilizers in general.
- An increase in corn farming in the U.S. Midwest, partly to meet a demand for ethanol fuel.
As a result, companies sometimes offer discounts to farmers who buy and apply their fertilizer to the surface of their fields in the fall – a practice that appears to significantly increase the rate at which it gets washed into local waterways.
The algae problem in Lake Erie that fouled the water that hundreds of thousands of people rely on for drinking, cooking and bathing last week was thought to have been successfully eliminated in the 1980s. Farming is the main culprit today, and climate change has become an "aggravating factor."
Lake Erie's Algae Explosion Blamed on Farmers