Managing natural areas can be frustrating

Staff Writer
Story City Herald

—by Steve Lekwa

Story County is blessed with several high quality public natural areas representing several important habitat types. Doolittle Prairie is one of the state’s best examples of wet pothole prairie once so common in our area. Robison Wildlife Acres, McFarland Park, and parts of the Skunk River Greenbelt offer glimpses of upland oak-hickory forest that was never common here where most of our forest land was and is limited to floodplains and valley walls. Colo Bog Wildlife Management Area offers some good examples of native marshland (wetlands that are a little larger, deeper, and more permanent than most prairie potholes). Although Native Americans are known to have used fire to alter their environment for centuries, there was a time long ago when these areas maintained themselves and their original diversity of plants and animals with little or no human influence.

Today’s natural areas are isolated islands in a sea of human-altered land. Managing them to maintain even a fraction of their original diversity is a big challenge. The influence of at least one component of our original landscape, large grazing animals like bison and elk, has been missing for at least 150 years. Their grazing behavior and food choices were quite different from the grazing of fenced cattle, sheep, hogs, and horses that replaced them. Grazing by wild, unfenced, and constantly moving animals served to increase the diversity of the habitats they used, while fenced domestic stock destroyed it. Modern managers use fire and even grazing when they can, but the ancient patterns and frequency of fire and grazing are nearly impossible to duplicate in today’s environment.

Almost all of our remaining natural areas suffered decades of domestic livestock grazing, and even where no longer grazed, exist under a constant rain of seed from alien invasive plants that can choke out native plants. Even some native plants now show invasive tendencies when they appear in habitats they were never part of or that now lack the natural controls that once kept them in balance with their neighbors. It seems that each habitat type has its own array of invasive plants to contend with. Wetlands can be overwhelmed by Reeds canary grass, an alien form of phragmites (reed grass), or purple loose strife. Prairies struggle to survive when invaded by Canada thistle, crown vetch, red clover, smooth brome, and a host of native and alien woody shrubs and trees that once were limited to the few forested valleys. Woodlands are being overwhelmed by Asian honeysuckle, buckthorn, autumn olive, and garlic mustard; all plants that can grow so densely that they block almost all sunlight and crowd out native plants. As if alien invaders aren’t bad enough, shade-tolerant maple, basswood, and ironwood are taking over the under story of oak-hickory uplands in some of our woods without the controlling influence of fire. Many species of native wildlife depend on nuts, and young oak and hickory trees can’t survive in the shade created by the faster growing species.

A recent walk through Robison Wildlife Acres showed the extensive work that’s been done to try to save the oak-hickory uplands. Much of the area’s forested land had become so shaded by invading honeysuckle and shade tolerant trees that only bare soil was left. Removal of these bushes and trees returned light to the forest floor and freed the old spreading oaks. A carpet of wild flowers and native sedges now cover areas that were eroding soil a few years ago. Sadly, the sunlight that allows native flowers and young oaks and hickories to thrive has also made the recovering forest floor more attractive to another invasive forest scourge, multiflora rose. Small roses are sprouting among the wild flowers. Garlic mustard doesn’t like full sun, but continues to increase in density and area coverage in spite of efforts to pull up and remove the plants. It seems that almost any management practice that can improve one aspect of a native remnant ecosystem is also likely to favor another form of alien invasive plant. Frustrating!