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THESE MAPS

SHOW how

fertilizer is

choking the

Great Lakes

By MATTHEW W. CHWASTYK, Jason Treat, and Kelsey Nowakowski

PUBLISHED NOVEMBER 17, 2020

Freshwater is vital to the Great Lakes Basin agricultural industry, which pumps some 400 million gallons of basin water every day for irrigation. The region supports 25 percent of Canada’s agricultural production and 7 percent of the United States’, but water quality, wildlife habitat, and fish stocks have decreased in recent decades as a result of high fertilizer use and other pressures.

CANADA

GREAT LAKES

BASIN

UNITED

STATES

Cropland

ONTARIO

GREAT LAKES

Basin

QUEBEC

L. Superior

MINN.

CANADA

ONT.

MICH.

WIS.

L. Huron

N.Y.

MICHIGAN

L. Erie

UNITED

STATES

PA.

OHIO

IND.

ILL.

Total cropland in the Great Lakes basins

28.2 million acres

Canada

9 million

acres

United States

19.2 million acres

Intensive monocropping…

Growing one crop on the same land each year is common. Row crops such as corn, soybeans, and hay dominate the southern Great Lakes region.

Total cropland

for soybeans

8.8 million acres

Total cropland

for corn

8.6 million acres

…requires a lot of fertilizer…

The longer a piece of land is used for a single crop, the more fertilizers are needed to replenish soil nutrients that can’t regenerate naturally.

Total cropland treated with commercial fertilizer, lime, and soil conditioners

19.7 million acres

Total cropland treated with manure

4.4 million acres

…which leads to

massive algal blooms.

Fertilizer nutrients such as nitrogen and phos­phorus drain into the tributaries that feed the lakes,

causing a range of adverse impacts.

Total phosphorus

concentration

Low

High

Lake Huron

Lake Superior

Lake

Ontario

Lake

Michigan

Lake Erie

Fertilizer-laden runoff leads

to a glut of nutrients.

Natural processes, fertilizer runoff, and sewage-treatment wastewater supply an overabundance of phosphorus and nitrogen to the lakes, leading to toxic algal blooms.

Phosphorus

Nitrogen

Fertilizer and manure, rich in nitrogen and phosphorus that are not taken up by crops, enter tributaries and lakes.

Oxygen

Algae feast on the excess nutrients, resulting in massive blooms that absorb sunlight and oxygen, suffocating plants and animals.

Algae

The dead plants and algae decompose; bacteria further rob the system of oxygen as they break down the organic material.

Sources: U.S. Department of Agriculture; Agriculture and Agri-Food Canada; Nasa; USGS; U.S. EPA; NOAA; USGS Upper Midwest Water Science Center

This Map shows how

fertilizer is choking

the Great Lakes

By MATTHEW W. CHWASTYK, Jason Treat, and Kelsey Nowakowski

PUBLISHED NOVEMBER 17, 2020

Freshwater is vital to the Great Lakes Basin agricultural industry, which pumps some 400 million gallons of basin water every day for irrigation. The region supports 25 percent of Canada’s agricultural production and 7 percent of the United States’, but water quality, wildlife habitat, and fish stocks have decreased in recent decades as a result of high fertilizer use and other pressures.

Lake Superior

Basin

Lake

Nipigon

CANADA

GREAT LAKES

BASIN

ONTARIO

UNITED

STATES

Thunder

Bay

CAN.

U.S.

MINNESOTA

Lake HURON

Basin

Duluth

Greater

Sudbury

Land cover

MICH.

ONTARIO

Cropland

Grassland

Scrubland

Forest

Wetland

Urban area

CANADA

UNITED

STATES

Georgian

Bay

Lake Michigan

Basin

WISCONSIN

CANADA

UNITED STATES

Green Bay

Toronto

Total phosphorus

concentration

Syracuse

Rochester

Hamilton

High

NEW YORK

Buffalo

MICHIGAN

Milwaukee

Lake

St. Clair

Lake ONTARIO

Basin

100

mi

Detroit

Erie

100

km

Windsor

Chicago

Low

PENNSYLVANIA

Toledo

Cleveland

ILLINOIS

Lake ERIE

Basin

Fort Wayne

OHIO

INDIANA

Intensive monocropping…

Growing one crop on the same land each year is common. Row crops such as corn, soybeans, and hay dominate the southern Great Lakes region.

…requires a lot of fertilizer…

The longer a piece of land is used for a single crop, the more fertilizers are needed to replenish soil nutrients that can’t regenerate naturally.

Canada

9 million

acres

United States

19.2 million acres

Total cropland

for soybeans

8.8 million acres

Total cropland

for corn

8.6 million acres

Total cropland in the

Great Lakes basins

28.2 million acres

Total cropland treated with commercial fertilizer, lime, and soil conditioners

19.7 million acres

Total cropland treated with manure

4.4 million acres

…which leads to

massive algal blooms.

Fertilizer nutrients such as nitrogen and phos­phorus drain into the tributaries that feed the lakes, causing a range of adverse impacts.

Lake Erie’s algal blooms have worsened over the past decade. Viewable from space, the blue-green, nutrient-­loaded water persists for weeks, threatening human health, drinking water, and wildlife.

12

Western Lake Erie

algal bloom severity

9

6

Algal bloom severity above 3 is harmful for water quality.

3

0

2005

2010

2015

2019

2002

Fertilizer-laden runoff leads to a glut of nutrients.

Phosphorus

Nitrogen

Fertilizer and manure, rich in nitrogen and phosphorus that are not taken up by crops, enter tributaries and lakes.

Algae feast on the excess nutrients, resulting in massive blooms that absorb sunlight and oxygen, suffocating plants and animals.

The dead plants and algae decompose; bacteria further rob the system of oxygen as they break down the organic material.

Algae

Oxygen

Sources: U.S. Department of Agriculture; Agriculture and Agri-Food Canada; Nasa; USGS; U.S. EPA; NOAA; USGS Upper Midwest Water Science Center