Cold water and gray forest and yet the river is welcoming. No wind means a flat surface, the only movement the ceaseless current carrying the canoe down, always down, descending the continent. The middle of November, more than halfway to winter, and a forecast in the fifties, and a free day — accepting the sudden offering of a river rendezvous in a season when such opportunities are not at all guaranteed.

There’s no one else on the water today, except two fishermen in a boat speeding upstream. There are no waterfowl, no startled wood ducks nor noisy geese. In a few places, small birds flush from sandy banks, scattering into the surroundings too quick to be studied. This loneliness offers a chance to see the river and its valley without distraction.

Slipping past bare banks, tan dead grass and homogeneous silver maples in dense floodplain forest make a wall of wood. The sideways angle of the sunlight feels like morning until about 2 p.m., and then evening begins. It will be dark by 5 p.m. and the whole afternoon is either morning or sundown. There is no midday. Shadows are long and the light is as gold as it gets.

The glassy water, leafless trees, and lack of any other noise means any sound carries far — a squawking pileated woodpecker or a crying eagle sound closer than they should. Falling leaves float down to the surface of the water, follow the fall south. The water is very clear, an amber-tinted window to the river bed several feet below, sand and wood and rock sliding underneath.

A backwater with a narrow opening on the main channel stretches upstream towards a noisy hidden waterfall which seems to recede into the bluffs, never revealed. Schools of minnows a foot below the surface catch the sun’s rays, glint golden in the amber tinted water. A little ice as thin and clear as a fine wine glass is hiding here, crumbling against paddle and hull.

Eagles are almost always in sight. Lazily following the river south. Catching the last rays of light hitting the tops of the trees. Singles and pairs and a few families with both adults and juveniles. In the trees, swooping over the water, or soaring around the bluffs.

A side channel with a sandbar at its entrance and ultimately impassable, but enough water to float a narrow winding ways into the woods. Exploration in search of something unspecified. Maybe a new passage, maybe a scenic view, maybe an odd observation about wildlife behavior. Perhaps a digression.

After the water runs out at a grassy old channel that hasn’t been submerged in some years, the return trip reveals evidence of beaver activity. A cache of sticks is stashed against the bank, where an underwater burrow probably provides access to a den. The banks are sliced by well-worn paths created by the rodents in their foraging. The other notable organism is buckthorn, the nasty non-native brush species that has infiltrated even the most remote parts of the St. Croix Valley.

Buckthorn’s leaves stay green and on the stems until much later in the season, and fall is often when it’s most obvious. It is scattered up and down the St. Croix, probably carried in the digestive systems of birds who eat the seed-bearing berries. Here, there are numerous large, mature specimens scattered through the floodplain. In one spot, where several bushes overhang a steep bank, its potential to cause erosion is on display. While most of the banks are held in place by shaggy grasses, under the buckthorn, the ground is bear. The plant releases toxins in its roots and creates such consistent shade that few plants can grow near it, leaving soil exposed.

Then I noticed the trails going up the banks again, and suddenly wondered about beavers and buckthorn. Wouldn’t it be wonderful if they somehow controlled its growth along the river? It was abundant in areas, but perhaps they ate enough to keep it in check. But as wood for food goes, it’s much different than beavers’ preferred diet of willow, aspen, and such. Buckthorn is a very hard wood, for one thing, and just looking at the stuff tells me it tastes bitter.

But there was no buckthorn in sight with teeth marks on its trunks, just a lot of plants reaching 15 feet in the air, still holding green leaves after everything else had gone brown and gray.

Then, in the shallow water near the bank, there were branches with green leaves. Closer investigation revealed a small pile of buckthorn branches, cleaved off cleanly with what were clearly beaver incisors. Looking at a big buckthorn bush on the bank, it appeared a beaver had harvested the branches from the lower reaches of the main stem. It had brought them down to the water, and then left them there.

Like most good science, the observation raised more questions than it answered. Whether or not beavers typically ate buckthorn was still up for debate. Why had it left the branches here? Was it a young one who took a while to realize the wood was no good? Was it an older one who knew the branches were palatable and was coming back for them?

I noticed few small buckthorn stems, and wondered if beavers eat the young plants and check the buckthorn population that way, while enough trees survive to get big enough to be safe from the teeth? If a streamside area gets overrun with buckthorn, will it drive beavers away? Could their many ways of engineering the ecosystem be replaced by soft banks washing away? Could we train beavers to eat buckthorn?

Later, a cursory search of scholarly publications revealed some oft-repeated observations from decades ago that beavers appeared to avoid buckthorn. A blogger observed beavers using buckthorn in dam construction. In any case, here there are both abundant beavers and buckthorn, and the above observations are offered to anyone with more to contribute.

Emerging from the side channel, the sun is about to slip behind the Minnesota bluff. It silhouettes bare trees and gnarled white pines, and then disappears. A chill chases close behind. Gold wisps glow in the sky.

There is little left to see and few questions to ask. Just the silent steady sweep of the river, perfect peace, beauty beheld by a fortunate few.

Reference

Knight, Kathleen S; Kurylo, Jessica S; Endress, Anton G; Stewart, J. Ryan; Reich, Peter B. (2007). Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): a review. Retrieved from the University of Minnesota Digital Conservancy, https://hdl.handle.net/11299/175602.

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