Growing Crops Too Close to Stream Banks Pollutes Minnesota Waterways
Washington, D.C. – Nearly 170 waterways in southern Minnesota get a grade of D or F because they lack the required protective strips of vegetation that prevent farm runoff from polluting nearby rivers and streams, according to a report card rating developed by Environmental Working Group.
Minnesota’s progressive shoreland management rule requires landowners to establish and maintain a 50-foot “riparian buffer” between farmland and waterways to reduce the amount of sediment and nutrients that wash off crop fields and into streams. Using a combination of aerial photography and digital mapping of the state’s waterways, EWG analysts evaluated 37 counties and found that only 18 percent – 87 waterways – had 100 percent of the required buffer zones.
“Polluted runoff from farmland is a major environmental and public health problem, but it is one that can be largely prevented in Minnesota and across the country,” said Craig Cox, EWG’s senior vice president of agriculture and natural resources and co-author of EWG’s “Broken Stream Banks” report. “Minnesota is a national leader in recognizing the importance of buffers between cropland and waterways. Better enforcement of the shoreland management rule presents a remarkable opportunity to improve water quality. ”
In EWG’s report, about 21 percent of waterways – 101 in all – got a failing grade because they had less than 60 percent of the required buffer acreage. Another 14 percent – 66 waterways – earned a D because only 60 to 69 percent of the buffer zones were in place.
The report, which includes interactive maps and detailed charts and tables on each county in southern Minnesota, found that the required buffer zones were even scarcer near smaller waterways. Small streams account for a third of the evaluated area but almost half the missing buffer acreage.
“The missing buffers along smaller streams are bad news for Minnesota’s water quality because small streams are more directly affected by cropland,” said Soren Rundquist, EWG’s landscape and remote sensing analyst and co-author of the report. “It is our hope that county officials who are responsible for implementing the rule will use our data as a tool for enforcement and education.”
The Minnesota River and its miles of tributaries are badly polluted largely because of runoff from row crops that reaches far downstream. As a result, sediment is filling up Lake Pepin on the Mississippi River near the Minnesota-Wisconsin border, where phosphorus regularly triggers noxious algal blooms. More consistent use of buffer zones could help reduce runoff by filtering and retaining sediment, storing and inactivating phosphorus and strengthening stream banks from eroding or slumping into streams.
“Stricter enforcement of the shoreland management rule won’t solve all of the pollution problems, but it would be a big step in the right direction,” Cox said. “Better enforcement would ensure that the water quality gains achieved by those landowners who do comply with the rule are not undone by others – often their neighbors – who do not.”
Photo courtesy of ESRI, Digital Globe