August 2010

The DNR communications team works with agency experts to develop the weekly questions and provide the answers. This feature addresses current DNR issues, interesting topics, or the most frequently asked questions from around Minnesota.





Earthworms make great fishing bait, but I heard recent research has discovered that they are a threat to Minnesota's forests, making them an invasive species. What sort of damage do they cause?

It really is true that all of the terrestrial earthworms in Minnesota – including night crawlers – are nonnative, invasive species from Europe and Asia. Invading earthworms eat the leaves that create the "duff" layer in forests and are capable of eliminating it completely. This layer is important to native plants and ground dwelling animals.

Studies conducted by the University of Minnesota and forest managers show that at least seven species are invading our hardwood forests and causing a loss of tree seedlings, wildflowers and ferns. In areas heavily infested by earthworms, soil erosion and leaching of nutrients may reduce the productivity of forests and ultimately degrade fish habitat. However, many areas of the state are still free from earthworm disturbance.

Because earthworms are non-native, it is illegal to release them into the wild, according to Minnesota Statutes 84D.06, which means anglers should dispose of unwanted bait in the trash.

- Jay Rendall, Invasive species prevention coordinator


Are lake levels around the state rebounding from their low-levels?

Due to above-average rainfall during the latter half of summer, lake levels in northern St. Louis County have rebounded from low elevations observed earlier in the season. Elsewhere, Lake Superior water level is down six inches from last year at this time and remains below the long-term average. Also, water levels on some other northern, central, and east central lakes are below average. Water levels on a few larger lakes in east central Minnesota lakes remain exceptionally low. White Bear Lake, on the Ramsey/Washington county border, is at or near its all-time record low level.

- Greg Spoden, assistant state climatologist



It is well documented that less than 1 percent of Minnesota’s native prairies remain intact. What is the significance of those that remain and of prairie landscapes as a whole?

Nearly half of all of Minnesota's rare and endangered species live on prairies, which make preserving these complex ecosystems critical to protecting the state's natural heritage. Prairies also supply habitat for a wide variety of wildlife species, reduce soil erosion, and provide important pastureland for cattle and other livestock. The challenge is keeping these few remaining prairie remnants healthy and vibrant. In their natural state, prairies were maintained by climate, fire and grazing by roaming bison. This allowed native plants to regenerate annually by removing dead grasses and keeping the landscape free from becoming shrubby and overgrown with tree species such as red cedar, box elder, elm, oak and aspen.

Today, controlled burns, haying and grazing can mimic these natural processes. Of course, too much disturbance can also be a problem. Season-long overgrazing, for example, can slowly convert a native prairie pasture to one dominated by exotic cool season grasses such as Kentucky bluegrass, and noxious weeds such as Canada Thistle and Leafy Spurge. Although it is not possible to recover all 18 million acres of prairies that covered Minnesota prior to European settlement, preserving what is left will protect a small piece of the state's history.

To visit a prairie near you checkout the following website:

- Jason Garms, DNR Ecological and Water Resources – prairie biologist



DNR Question of the Week Archive