The Duluth News Tribune examines a stunning new report that analyzes the extent to which humans have dramatically changed the course of Minnesota streams and waterways.
The Minnesota Pollution Control Agency and Minnesota Geospatial Information Office's two-year study is the first to quantify just how many miles of streams are no longer running their natural course, the newspaper reports. It concludes that more than 80,000 miles of streams – over 49 percent – have been shifted by human activity, including for agriculture, dams and development.
The study offers significant insight for state pollution experts. Altered waterways often result in higher sediment flows, higher levels of pollutants flowing to other waterways and decreased marine life habitat.
The new study will "help the MPCA in working with local partners to develop watershed restoration and protection plans throughout the state’s 81 major watersheds," according to the agency. Restoring a stream to its natural path, or maintaining a stream that has not been altered, can help protect or improve water quality, agency officials say.
The agencies compared aerial photos dating back to the 1930s with present-day images, and analyzed high-resolution elevation data, according to the Pollution Control Agency.
Changes were especially striking in the metro area and in farm areas in central, western and northwestern Minnesota, where many straight-line ditches were dug for farm use. In some central and northwestern Minnesota counties, more than 90 percent of stream miles have been altered in the last eight decades, the News Tribune notes.
Here's more about the study's methodology, including some aerial images dating to the 1930s.