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Dense tree cover can be hard to come by in farm country. But new research shows that more trees close to rivers and streams are linked to higher biodiversity.
Researchers at the University of Illinois found evidence of an additional land species for every 10% increase in trees and shrubs alongside waterways, which scientists call riparian buffers.
The researchers collected water from streams and analyzed any traces of DNA they could find in the samples. The process is called environmental DNA metabarcoding, or eDNA.
“We detected bobcats that have had a big population recovery in Illinois over the last few decades,” said Eric Larson, who leads the lab that conducted the study. “We detected bats. We detected box turtles. I think those benefits to wildlife also have benefits to people.”
Bobcats were hunted to near-extinction in the Midwest, but they’ve been making a comeback since the 1990s.
Larson said this is one of the first studies of its kind in the U.S. The sampling method can be as easy as throwing a bucket on a rope off a bridge, so volunteers or farmers can collect samples to support a wide range of conservation research. Larson said eDNA can be used as a tool for landowners to see whether certain conservation practices they’re trying, like riparian buffers, are actually working on their farms.
Olivia Reves, the study’s lead author, said she hopes the research leads to a wider adoption of riparian buffers.
“We have really interesting biodiversity in this area,” Reves said. “We're doing our best to give these organisms a voice and fighting chance in this landscape.”
Some states require riparian buffers by law. Minnesota is one, along with California and Alaska. The Minnesota Buffer Law mandates at least 30 feet of perennial vegetation — or plants that live for multiple years — along public lakes, rivers and streams to help filter runoff and prevent soil erosion. It also requires at least 16.5 feet of vegetation along public ditches.
There was initially pushback from farmers and landowners when the law first passed in 2015, said Tom Gile, the resource conservation manager with the Minnesota Board of Water and Soil Resources. He said two amendments to the law have since added some flexibility and alternatives for places where a buffer doesn’t make sense on the landscape.
Enforcement comes from local soil and water conservation districts, which Gile said are also working to help farmers bring their land into compliance.
“There wasn't very good research or good surveys to assess where there were and weren't buffers in the landscape prior to the reporting mechanisms that we put into place,” Gile said. “As of today, we sit over 99% compliant with the law.”
Gile said there tends to be cleaner water and more wildlife present in areas where there are buffers in the state. But he said it can be challenging to know how much of that is due to the buffers themselves.
“It does help with the general maintenance and operations of our drainage systems in the state,” he said. “It helps by, in some landscapes, [keeping] a little bit more sediment out, which is the main reason that they need to do maintenance in the ditch systems... and just generally it can provide a little bit of additional habitat along the way in those corridors.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
