The area which I’ve selected to observe is one which has always fascinated me. At Fort Whyte Alive, an environmental education centre in Winnipeg, Manitoba, there is a very thin strip of land roughly 300m long and 10m wide between two man-made lakes which was formerly part of a dyke system. This peninsula consists entirely of clay soil, and is fairly flat with steep banks. It rises anywhere from 2-5m above the water level. There are several small promontories of limestone rock spaced equidistant along each side of this peninsula, which are part of an anti-erosion system put in place some time in the early 1980s. In 1997, flooding of the Red River caused these lakes to fill well above their normal levels, resulting in a breach in the East end of the dyke which rendered this peninsula functionally inaccessible from the main visitor area despite being physically located very close to it. Since this flooding event, the peninsula of interest has remained the least accessible area of land at Fort Whyte to humans, only being reachable on foot by leaving the closest point of designated trail into an off-limits zone and trekking along approximately 1 km of deer trails through mixed grassland and bush. The peninsula is, however, easily accessible by foot once the lakes freeze over in the winter, but human presence is kept minimal by nature of the heavily eroded, near vertical banks which are very difficult to climb. As such this peninsula has seen almost no human influence in the last 23 years aside from the rare visit by staff members (including myself).
Image: The peninsula of interest, marked within the red oval.
Image: A section of field journal illustrating two representative stretches of shoreline; a heavily eroded section dominated primarily by grasses (left), and a less eroded section dominated by young trembling aspen and sandbar willow.
My visit to this peninsula involved skating on the frozen lake up one side and down the other, on Dec. 11 2021 at around 11:00 am. I was a sunny day with a temperature of -2°C. Despite the presence of snow, it was still fairly easy to distinguish the shorter vegetation and grasses. Most stretches are heavily eroded, with 2+ metres of vertical clay cliff overhanging the water. A few stretches have a more gradual incline toward the water, but are still steep and actively eroding. A few stretches are dominated entirely by grassland ecosystems consisting of grasses and wild flowers. There are some large patches of young aspen forest that appear to have recently colonized some of the grassland areas. There are maybe 30 cottonwood trees scattered along the length of the peninsula, some maybe 30 years old, some maybe 2. Lower down nearer the water’s surface there are some stretches of land with thickets of sandbar willow. There are only about 5-10 trees growing in this lower area, mostly non-native golden willow and siberian elm, with a few young cottonwoods. I suspect they seeded in naturally within the last 20 years. There seems to be a distinct lack of shrub species, aside from sandbar willow. Really, there seems to be a lack of riparian species representation despite this peninsula being very much a riparian zone. There is no aquatic emergent vegetation anywhere along this peninsula.
No animal tracks were observed due to the lack of snow. So little snow, in fact, that most of the surface of the lake ice was free of it.
The entire length of the peninsula appears to be actively eroding due to the steep clay bank being undercut by the water. I suspect this may be due largely to the lack of protection that would be offered by the riparian vegetation which one would normally expect to be present if this area were in a natural state that has remained stable for a long period of time.
Image: A stretch of the peninsula facing particularly severe active erosion. Note the predominant vegetation type above the erosion appears to be grass, with only 3 trees in sight.
From looking at the vegetation and drawing on my knowledge of species succession, I suspect that this area was originally an open grassland ecosystem when the lakes were quarried, and a natural succession of plant species has not yet had time to take place. The nearest natural riparian ecosystem is the Red River, the closest point being 5 km away. Previously, the Fort Whyte area was predominantly a mix of tallgrass prairie, upland oak forest, and industrial area, surrounded by farmland. Perhaps there is just not a large enough population of riparian vegetation close enough to this area to spread many seeds into it, and this is preventing a new community of riparian vegetation from successfully establishing.
I can boil down the thoughts I had during this observation to 3 lines of questioning:
- Is the amount of active erosion related to the presence or absence of riparian vegetation?
- Why are there so few riparian species present?
- Could the introduction and establishment of riparian species by humans stop this erosion?
Great first blog post, very detailed! So this peninsula was originally a man-made dyke but has been left to natural processes since it was built or at least since the 1997 flood? Is there no riparian vegetation in some areas because of the steep clay banks that you mention? Similarly a lack of emergent aquatic vegetation could be because of the steep banks as most species need less than 2 m of water. I think you are on the right track with your questions though as you progress to the next blog posts and first small assignment you will have to think of what you can measure. It could be hard to answer questions 2 and 3 without a larger experimental study.