Heavy Rains, Runoff, Toxic to Wildlife

Lake Erie is experiencing a one-two punch of heavy rains and excess farm runoff that influences the magnitude of algae toxic to wildlife and humans.

National Wildlife Federation, 2013.
National Wildlife Federation, 2013.
In a recent report: Taken by Storm: How Heavy Rain is Worsening Algal Blooms in Lake Erie, NWF examines the relationship between large rain events, nutrient runoff, and harmful algal bloom size, focusing on the input from Maumee River in Ohio.

The report highlights storm “snapshots” of seasons with heavy rain — the type expected to be more frequent with climate change — and that season’s levels of farm runoff, and subsequent toxic algae blooms.

Why is it toxic if it’s algae? Why does excess farm runoff make a difference?

There is both good and bad algae.

Algae, particularly green algae, play an essential role in forming the base of the aquatic food web. These organisms are one of the most basic forms of life, requiring only light, warm temperatures, carbon dioxide, and nutrients to grow.
Wake from a small boat in July 2011. Credit: NOAA/NCCOS
Wake from a small boat in July 2011. Credit: NOAA/NCCOS
Phosphorus from excess farm runoff typically serves as the “growth-limiting” nutrient for algal growth because it is present in low concentrations. In larger quantities, however, phosphorus can stimulate excessive growth of algae. While hundreds of beneficial species of algae live in Lake Erie, some, like blue-green algae cyanobacteria, can be hazardous. Excessive phosphorus from farm runoff enables their growth.

Climate Change and Heavy Rain

Wet springs, followed by dry summers are the perfect recipe for toxic algal blooms.

Rainfall and its contribution to harmful algal blooms.
Rainfall and its contribution to harmful algal blooms.
Climate change is causing the Midwest/Great Lakes region to experience warmer air temperatures and large rainfall events—along with swings of drought. Heavy precipitation events are particularly on the rise. Since 1958, days with very heavy precipitation have increased by 31 percent.

Additionally, the seasons are changing. Warm conditions in the late winter or early spring can cause rain on snow events, expanding the time period of runoff potential. Although we identify a few storm snapshots in this report, the wettest spring on record for Ohio produced a memorably massive harmful algal bloom in 2011.  This is an alarming snapshot of disaster to Lake Erie if record-breaking rains and excess nutrient loads continue.

Scientists recently ran climate scenario models that show larger rain events of rainfall amounts of about 1.2 inches, have the potential to be twice as frequent over western Lake Erie basin.

Impacts on Wildlife

Credit: Ron Nichols.
Credit: Ron Nichols.
Lake Erie is a vital ecosystem that sustains many species of wildlife. The area provides rich food, cover, and nesting habitat necessary to make it a favorite for birds. Home to a $26 million bird-watching industry, some  of the species of birds that can be found are American black duck, Harlequin duck, Great Blue Heron, American bald eagle, blue-winged teal, king rail, wood thrust, geese, sandpipers, and the Ohio state bird, the cardinal. Lake Erie’s freshwater fish habitat is well-suited for species like bluegill, walleye, perch, and lake sturgeon. Amphibians and reptiles include the endemic Lake Erie watersnake, Blanding’s turtle, painted turtle, and many species of frogs and toads. Other wildlife species that depend on a healthy Lake Erie include white tail deer, fox, skunk, otters, and beaver.

Lake Erie 2010. Credit: Lake Improvement Association\Flick Creative Commons.
Lake Erie 2010. Credit: Lake Improvement Association\Flick Creative Commons.
Toxic algae, from an organism called microcystin, is essentially a liver toxin. It can sicken people or wildlife by affecting the liver or the skin.

But this is Lake Erie, and I don’t live there

Lake Erie is a surrogate example of toxic events happening in other parts of our nation’s waters, including – the Mississippi River, Gulf of Mexico, and Chesapeake Bay. Keeping these waters clean of toxic runoff is highly important to our own health, and the health of wildlife.


  • Implement farm policy that incentives and assists farmers to apply fertilizer at the right time and the right rate. For example, applications on frozen ground or before a heavy rain will likely wash right off the land and into the waterways. Farmers can prevent fertilizer and money lost by considering any heavy rain in the forecast.
  • Support wetlands restoration. Wetlands help filter excess runoff.
  • Protect our communities from flooding events expected due to climate change.
  • Reduce the chances of record-breaking rain by reducing global warming greenhouse gas emissions through transitioning to a clean energy economy.

Learn More and download Taken By Storm here!