St. Croix Riverway Time and the River: A History of the Saint Croix

CHAPTER 1:
Valley of Plenty, River of Conflict (continued)

The Ecological Impact of the Fur Trade

The landscape of the Upper St. Croix River was changed in subtle ways by the growth of the fur trade among the Chippewa and the Dakota. The presence of herds of elk and buffalo in the region declined dramatically as more hunters sought these large game animals with more effective weapons. There is evidence that in the seventeenth century buffalo roamed as far north as the Pine Barrens between the St. Croix and the Brule rivers. By 1820 elk and buffalo were both rare in the St. Croix valley. Schoolcraft claimed that the last time buffalo crossed to the east bank of the Mississippi was in 1820. Twelve years later traders reported that Dakota hunters in the Trempleleau River valley killed the last bison in Wisconsin. The elk, their numbers greatly reduced by hunting, survived longer. In 1854, when white settlers reported seeing several elk along the Sunrise River in Chisago County, Minnesota it was the cause of some excitement. The Dakota, when they were sole masters of the St. Croix valley, had regularly set wild fires to enhance elk and bison habitats. The small prairie openings thus created helped to sustain the grazing animals. The Chippewa were less aggressive in the use of fire as a tool of game management. As the fur trade grew and the Chippewa presence in the valley increased the herds of grazers disappeared and the prairie openings yielded to vegetation succession. Maple-basswood forests replaced many of these openings along the river. [56]

As elsewhere in the region beaver were the most relentlessly hunted species in the St. Croix country. While beaver existed throughout the watershed, the upper portions of the valley, especially the upper Namekagon and tributaries such as the Clam, Snake, Yellow, and Totogatic Rivers, were superb habitat. Nonetheless, the beaver population of the region was likely in severe decline as early as the beginning of the nineteenth century. A drastic reduction in the beaver population of this stretch of the St. Croix and Namekagon valleys would have had a significant impact on the landscape. The beaver, more than any other creature save man, has the ability to consciously alter its environment. The industrious rodent does this in two ways, by impounding water to create beaver ponds and by felling trees for food.

The beaver builds dams across streams to create ponds that provide the beaver with a watery moat that keeps predators, such as the gray wolf or the wolverine, at bay. Beaver ponds render swift flowing streams into quiet, calm impoundments of water often an acre or more in size. In a northern hardwood forest like the St. Croix it would not be unusual to have numerous beaver dams on one very small forest stream. A study of beaver in Voyageurs National Park identified 2.5 beaver dams per kilometer of stream, with the result that well over half of the length of all streams was transformed into beaver ponds. The wetlands created by the beaver formed habitat for other important fur bearing animals as well. Muskrats and otters made their homes within the ponds. Mink and raccoons hunted frogs, turtles, and snakes around the margins of the pond. The edge effect of the wetland-forest interface fostered a diverse array of other animals as well, from waterfowl to deer and moose. The hydrologic effect of thousands of beaver ponds within the valley was to slow the flow of the tributary streams and moderate flooding along the entire valley. Ponds trapped sediment carried by streams, keeping nutrients in the forest, and filtering the water that was eventually discharged into the St. Croix. [57]

A beaver population of thousands within the St. Croix valley affected the forest as well as the river. The beaver is one of the most voracious browsing animals. Although moose, deer, and elk are normally seen as the major browsing species in the forests of the Upper Midwest, the beaver has much greater impact on forest vegetation. The difference with the beaver is that unlike the other grazing animals, its impact is restricted to areas within a hundred meters of water. Beaver tried to extend their range slightly by building canals, a foot or two wide, leading away from streams and into the woods. But this amazing behavior reinforces the fact of the beaver's aquatic nature. Yet, in spite of this limitation the beaver still manages to consume a vast amount of wood, leaf, and roots. A study of beaver at a single northeastern Minnesota pond revealed that each beaver felled 1,400 kilograms of woody biomass per year, substantially more than moose grazing in the same area. In fact the study concluded that the beaver colony harvested twice as much biomass as a herd of Serengeti ungulates. Not only was the beaver colony an intensive grazer it also was very selective, favoring certain tree species such as aspen and turning its nose up at alder or conifers. After several decades of beaver activity forests near their ponds were greatly changed, moving from aspen or paper birch dominated stands to a more diverse patchwork of shrubs and trees. [58]

Multiplied throughout the valley by the thousands of lodges and dams, the mini-environments created by the beaver encouraged diversity between both flora and fauna. Because of the beaver the St. Croix was clearer and less prone to flooding. The water table was higher and throughout the valley springs were more abundant. Trappers wrought havoc on the beaver landscape. Between 1800 and 1820 the beaver was all but wiped out along the St. Croix and other streams in the region. In 1800 fur traders reported a harvest of eight thousand beaver skins for the entire Dakota trading area, of which the St. Croix was only a small part. Yet by 1820 the beaver harvest for that same area was a paltry 760 pelts. [59]

The dramatically sudden over-trapping of the beaver brought changes to the valley, but only gradually. Beaver ponds endured long after the industrious rodents had been eliminated. It would have not been until the period after 1840 that the impact of the decline of the beaver would have been fully felt, but by this time a new group of dam builders was busy on the upper river. Loggers manipulated the water levels on the St. Croix and its tributaries in ways that would have impressed Castor canadensis, thus obscuring from the historical record the impact of the fur trade on the flow of the river. What is clear, however, is that the loss of beaver meant an end to unique pond habitats and the elimination of the forest's most voracious herbivore. "The features of the country have undergone a change," an early settler wrote of Burnett County. "The towering pines have decayed or been leveled by the woodsman's axe. Some small lakes have receded, and tall grasses wave and willows grow where once the ‘kego' [fish] sported in the clear blue waters." Some early settlers contended that the "sun drew the waters up into the heavens," and did not see the loss of the beaver a generation earlier as the cause. All they saw was the result, dry fields ringed by the bleached shells of freshwater mussels "and by the ineffaceable mark of the water breaking upon the beach and undermining the rocky ledges." [60]

Figure 7. Upper St. Croix and Namekagon Fur trade and Indian Sites
(click on image for an enlargement in a new window)