Giant, bobbing bog threatens docks on northern Minn. lake

A bog the size of a professional baseball field is on the move in North Long Lake. The 3-acre piece of wetland has destroyed docks while bouncing around the lake near Brainerd.

Sue Galatowitsch, professor of fisheries, wildlife and conservation biology at the University of Minnesota, said a bog is a mat of wetland vegetation that floats on the surface of a lake, usually attached to the shore. She says they sometimes break loose — like the one now floating on North Long Lake.

"Probably every year or two, there's a report of an exceptionally large one, sometimes even larger than this one," Galatowitsch said. "Most of the time, they're much much smaller and not quite this menacing."

High water often lifts the bogs loose from their roots and moves the plant mat somewhere else in a lake, and Galatowitsch said sometimes they are deliberately beached.

"Those are oftentimes difficult things to accomplish, but even trying to corral it and just sort of keep it away, especially from navigation," Galatowitsch said.

She said the best thing to do is to steer the bog away from docks and let it become anchored to shore on its own.