Kevin Jacobs
Rich Higgins
March 13, 2000

Since white settlement of Southeastern Minnesota, large-scale changes have altered the landscape from one of a mixture of deciduous forests, oak savannas, prairies, and wetlands to one dominated by agriculture. Rice County was in a band of deciduous forest that ran the length of the state, and specifically was in a region of Big Woods forest. Big Woods is the peak of deciduous forest development, densely populated by maple and basswood trees, as well as oaks, ironwood, elm, hickory, butternut, birch and aspen (DNR webpage). In 1850, Big Woods covered 3,000 square miles (Tester, p. 25), comprising 62% of the region’s landscape, but now agriculture covers 62%, and Big Woods have been reduced to 6.9% (Milbert, p. 10). The transition area from the forests to the prairie was dotted with oak savannas. Though most of the prairie lands of historic Minnesota lie to the west of Rice County, there were significant patches of it within the county. Now, statewide, only 1% of the original 18 million acres remains (DNR webpage). Despite the encroachment of farming practices into prairie ecosystems, the prairies could adapt, initially, by spreading their grasses into grainfields, haylands, pastures, fencerows and roadsides, though now even this is not sustainable for the prairie ecosystems (Milbert, p. 12). The region’s riverine ecosystems have been affected, as well, as dams and channel walls have been constructed to control flooding, and agricultural runoff has increased toxicity and sediment build-up (McKone chat; Milbert, p. 13).

The fauna of all these ecosystems has been greatly affected as their habitat has been decreased in size and health. Forest fragmentation has weakened the genetic stability and disease resistances of many species. As the distances between forest patches has greatly increased, it has become more difficult for the resultant small populations to withstand local environmental variations because they do not have the ability to spread to other, more favorable habitats. The prairie loss has left patches of prairies too distant from each other to accommodate the limited dispersal distances of certain species. The death of these species has lowered the biodiversity -- a measure of ecosystem health -- of these patches. Dams have divided the Cannon River so that fish species are unable to navigate upstream segments, which not only affects the fish populations, but also the mussel enclaves that depend on the fish for translocation of this primarily sedentary bivalve’s eggs (McKone chat).

Debate continues, and often stagnates progress, about how to relieve the anthropogenic pressures put upon the ecosystems. There is something called the SLOSS debate concerning the advantages of establishing single large or several small reserves (Cunningham and Saigo, p. 326). A compromise between restoration of native ecosystems to their pre-1850 state and further human development of the land lies in the establishing of corridors that connect these fragmented habitats. The theory of island biogeography, articulated in 1967 by Robert H. MacArthur and Edward O. Wilson, outlines that a population’s abundance and extinction rate are functions of habitat size, and also that there is a direct relation between patch size and immigration rate (Cunningham and Saigo, p. 95). It follows that, while the size of a patch and its proximity to other patches are both important to maintaining biodiversity, the size is usually the more influential of the two factors (MacArthur and Wilson, p. 22; Cunningham and Saigo, p. 286). However, MacArthur and Wilson note that, as immigration to a patch increases, the patch’s size becomes less relevant (MacArthur and Wilson, pp. 22, 31). So, in our situation of human domination and financial commodification of the land and the habitats, the battle to increase size of habitat should be waged strategically so that habitat restoration increases migration rates within the ecosystem as quickly as possible. Thus, corridors, while increasing the size of the overall habitat, will promote migration by connecting smaller patches. The corridors will facilitate interbreeding as well as provide escape routes if conditions in one patch become unfavorable (Cunningham and Saigo, p. 327).

We think corridor creation will be more beneficial than common efforts to simply increase the areas of existing patches. As we have stated, dispersal distances can be accommodated in corridors and immigration will be fostered. However, corridor width is also an important consideration. Because corridor establishment is a form of ecosystem restoration, we must work towards attaining a minimum area-to-perimeter ratio. This ratio will manifest itself in the width of corridors. A corridor that is too narrow will not have enough core habitat. Instead, the corridor would be mainly a buffer/transitional habitat, and therefore would be subject to amounts of sunlight anomalous to the natural habitat. This buffer zone would also be more susceptible to disturbances from adjacent farmland and human activities.

Rivers are perhaps the most efficient natural corridors (McKone chat). They allow plant and water biology to move quickly and smoothly between ecosystems. They are also a general corridor because they are a channel for both aquatic and terrestrial flora and fauna. Everything from walleyes and duckweed to spotted skunks and cottonwood trees benefit from the river’s flowing corridor (CRWP webpage). The bank habitat of river corridors need be only a minimum of five to ten feet in width to be effective (McKone chat). Therefore these corridors tend to be fairly easy to establish and maintain. Threats to these corridors include concrete embankments and channels that might discourage semi-aquatic mammals such as the mink and beaver from using the bankless river in developed areas. Other threats include dams, fertilizer and human transportation runoff, wastewater treatment effluent as well as course alterations for irrigation.

By contrast, prairie ecosystems are more fragile and in a state of extreme decline. It was our initial intent to focus this project on the feasibility of developing effective prairie corridors. However, we soon learned that there is so little original prairie in Rice County that more of this habitat would be encompassed in the corridor network than in the connected enclaves. Early on, prairies were seen as farmland waiting to be plowed, as it was easier to clear prairie than to clear forest. Additional prairie loss occurred because natural fires were suppressed by the settlers, and this allowed the Big Woods to encroach onto land previously occupied by the prairie habitats (Tester pp. 80-81). While corridors will be a positive asset to prairie restoration in the future, efforts first need to be focused on allowing the prairie ecosystems to reestablish more of a foothold in the region. Increased political and public awareness, as well as education about prairie importance are key steps that can be taken now. More scientific actions to be taken include seeking out rare prairie species for preservation (DNR’s Scientific and Natural Areas program) and seed collection and distribution among isolated enclaves (McKone chat).

As discussed earlier, the Big Woods forest dominated in the area with its dense maple-basswood growth. In addition to the sugar maples and basswood trees, it is currently home to understory species such as wild geranium, leatherwood, bloodroot, and wild ginger and animal species including silver-haired bats, white-tailed deer, Franklin’s ground squirrels, and timber rattlesnakes (DNR webpage, CRWP webpage). While there is still much biodiversity within the remaining Big Woods, there are many rare and protected flora species whose numbers have severely declined, including the trout lily, crow-spur sedge, and small white lady slipper, and fauna like the willow fly-catcher, coyote, and the massasauga (CRWP webpage).

Certainly, agriculture has contributed greatly to habitat loss. But there are still some large stands of Big Woods in Rice County that have been protected. Nerstrand Big Woods State Park remains the largest habitat area, and to connect it by a corridor to the Cannon River Wilderness Area County Park and the Cannon River Trout Lily SNA would be a major benefit to biodiversity in these landmark enclaves. The Trout Lily SNA is protected habitat for the endangered Minnesota Trout Lily, and to connect it to the Cannon River Wilderness Area would require only approximately a 1.8-mile corridor north along the Cannon River, native habitat to the lily. This 1.8 miles would connect the 3.3 miles of river that run through the SNA and the 4.6 miles that flow through the Wilderness Park, constituting just a 23% increase in distance. As we have mentioned, corridors along streams are the easiest to establish and maintain. To connect the state park at Nerstrand would be more difficult, though. The corridor would have to stretch 1.8 miles west along a Prairie Creek tributary to Caron County Park, and from this park, continue northwest for 2.4 miles (1.6 of which is along streams, fortunately) to the Cannon River Wilderness Area.

According to Dick Peterson, the Rice County district forester, the majority of the land that separates these areas is farm land, with the remaining fraction of land either abandoned or otherwise developed. To obtain the land for these corridors we must either find funds to purchase the land from the land owners or pay them to undertake the restoration themselves. In many cases, this restoration merely entails allowing nature to take its course on the land and does not necessitate additional plantings. In others, some planting would be required. Either way, funding is crucial to make the creation of corridors in Rice county a reality. Bearing this in mind, we set our sights on possible avenues of fund raising. The DNR has organized several grant programs that would apply to the predevelopment and development stages of the corridors, as well as some that could contribute to upkeep and maintenance. However, there remains a possibility that municipal and county governments as well as non-profits such as the Cannon River Watershed Partnership (local scale) or the Nature Conservancy (national scale) may be willing to contribute. Among the DNR programs are research programs such as the Minnesota Natural Heritage Program and the Scientific and Natural Areas Program that could provide oversight. Financial assistance programs and grants such as the Minnesota ReLeaf Program, the Conservation Partners Grant Program, and the Forest Stewardship Program are blanket programs that cover many types of forest restoration often on private lands. Two programs that apply directly to the corridors we proposed above are the Stream Bank Maintenance Grant Program and the Wild and Scenic Rivers -- Acquisition Program. These focus on encouraging and compensating county governments and landowners for streambank habitat restoration.

One of the potential problems with forest corridors in this area is the possibility of the soils having been degraded or otherwise too altered by the fertilizers and chemicals applied by agriculture. Also, once the corridors are established, human disturbances may be too great in an area, discouraging animal use in that area. Such disturbances might be noise and dust from nearby use of agricultural equipment, as well as activity in the corridors by hunters and bikers. This speaks to the aforementioned issue of buffer zones and the width of the corridors. There is no concrete theory on how wide corridors should be, as, in most cases, the stewards will take whatever land they can obtain. One theory is that these strips of natural land should be able to accommodate two, side-by-side, fully-grown individuals of the largest native tree species (Sellers chat). Peterson suggests more land than this – that approximately a fifth of a mile would be adequate, as it would be sufficient to the needs of the native animal with the largest range – the white-tailed deer.

This exposes the biggest problem with the practicality of management of these corridors. Technically, the native animals with the largest ranges are not deer, but are Big Woods top predators – the coyote, wolf, bobcat, and black bear. In establishing the corridor to help bring about a stable and healthy ecosystem, it would be important to introduce these top predators to manage populations such as that of the deer. The lack of these predators in areas of mixed human development and forests has created deer abundances that are nuisances to landowners and that upset ecosystem equilibrium. Therefore, these corridors may not be supported by the affected landowners because of the possibility of deer grazing on agricultural land. Also, to manage this population with top predators is unrealistic, because landowners and townspeople will not want wolves and bears roaming the area. Until (or, if ever) the corridors and habitats are large enough to sustain and contain top predators, controlled, selective hunting may be the best alternative to natural management.

In an area such as Rice County, where widespread habitat restoration would be out of the question, corridor networking is the wisest option based on its practicality and biological effectiveness. Corridors are the best compromise between continued rampant human development and ignorant restoration of natural habitat. In our landscape of fragmented native habitats, to improve the state of the metapopulation depends first on increasing migration rates and escape routes, and corridors will do this. Prairie corridors, unfortunately, are not a possibility anytime in the near future. But riverine corridors are much more practical, and would serve not only as riparian connections, but would be integral to deciduous forest ecosystems as well. We propose the establishing of two corridors in Eastern Rice County, along rivers, that will connect three mixed lowland deciduous and Big Woods ecosystems -- the Trout Lily SNA, the Cannon River Wilderness Area, and Nerstrand Big Woods State Park. These are three large areas of relatively undisturbed habitat, and their networking will also integrate a fourth area called Caron County Park.

The next steps are to identify the landowners to be affected, contact them about their possible roles in the ecosystem restoration, and also to obtain funding from agencies to compensate the landowners. Once the corridors are established, scientific monitoring of their growth and natural use must be conducted in order to learn how to improve site selection and establishment of future habitat patch connections. Other corridors in the future might connect the River Bend Nature Center lands on the Straight River in Faribault and the Cowling Arboretum in Northfield on the Spring Creek and Cannon River. Each of these areas is within only a couple miles of our proposed networked ecosystem. Corridors can connect us to our natural past and our natural future.

References

Conversations

Literature

• Cunningham, William P. and Barbara W. Saigo, 1999. Environmental Science: A Global Concern (Fifth Edition). New York: The McGraw-Hill Companies, Inc.
• MacArthur, Robert H. and Edward O. Wilson, 1967. The Theory of Island Biogeography. Princeton: Princeton University Press.
• Milbert, Dan. Managing Landscapes in the Big Woods Ecosystem. Minnesota Department of Natural Resources.
• Tester, John R., 1997. Minnesota’s Natural Heritage: An Ecological Perspective. Minneapolis: University of Minnesota Press.

Webpages

• Minnesota Department of Natural Resources webpage. http://www.dnr.state.mn.us/
• The Cannon River Watershed Partnership, Faribault, MN webpage. http://www.crwp.net/