From Prairie to Shield

{This article was originally published in the Atikokan Progress, October 9th 2024}

I always thought of Manitoba as but a lush and vast prairie region; and indeed - it is vast, boasting more than 14,000 farms province wide. But as I drove home after a trip to Winnipeg, first through the town of Ste. Anne, passing by the water park near the Paradise Village neighborhood, then into Richer and beyond, the view outside my window transformed. Seemingly within a blink of an eye the plains vanished, giving way to lush greenery.

The Province of Manitoba separates its geography into fifteen distinct eco-regions, each with a unique shape, size, and ecology. The region I associated Manitoba with, having within it a higher population than all others combined (Winnipeg alone accounts for nearly sixty percent of the province's population), was the Lake Manitoba Plain. And this is understandable - not only does the region have vastly larger populations, but it also contains productive and rich soils suitable for large scale agriculture. In geographical terms, however, the province has a diverse ecosystem.

An eco-region we know well in northwestern Ontario is the Lake of the Woods, and in fact this sprawling wetland extends to southeastern Manitoba, forming a western edge of the Canadian shield. Sloping bedrock of rolling watery uplands and lowlands characterize this terrain. Nested in between forested bedrock to the east of Lake Winnipeg and agricultural plains to the west of Lake Manitoba lies a thin stretch of land called the 'Interlake Plain' ecotone (meaning, transition between two biological communities). Researchers from Agriculture Canada described it as “a mosaic of farmland and forest, marking the southern limit of closed boreal forest and northern extent of arable agriculture”. When driving through Ste. Anne, this couldn't be any more apparent.

{Satellite image of the Northwestern Ontario, Minnesota, and North Eastern Great Plains Regions}

As part of my fascination with this ecotone, I spoke to biologist Brian Jackson. During our conversation, he provided a wealth of knowledge related to the environmental history - and future - of the region. He began by explaining the critical role of the water cycle in shaping ecosystems. Simply put, when there is greater evaporation than rainfall, the land will be dryer, and have less vegetation. Across North America, precipitation decreases gradually as you travel west; soils become dryer and consequently face challenges of drought, a problem Jackson said Alberta is dealing with currently.

To the east, as the ratio between precipitation and evaporation shifts, and there is more groundwater in the system, the capacity to support dense forests, plants, and other vegetation improves. The wetness of the Lake of the Woods is heightened by the Canadian shield, which traps water overground. Within the Interlake plain ecotone, this ratio is close to one. Here, soil can support forests - but of a different type. Coniferous forests dominated by Pine and Spruce fade, as Aspen takes over as the primary species. This is also where visible bedrock diminishes, and the first signs of a flatter terrain become noticeable. One could only imagine the wonder of the early fur traders, perhaps voyaging down Pigeon River, when they finally reached a prairie landscape of easier mobility.

But before these traders arrived on flat lands (at least, if they were taking the Great lakes route as opposed to Hudson's Bay), they would have passed through an ecoregion the Ontario government calls the 'Agassiz Clay Plain'. Today, the region is home to the towns of Emo and Fort Frances, known for their ability to support agriculture. This region, Jackson said, is just south of the Canadian Shield, which appears around Nestor Falls.  'Agassiz' takes its name from an ancient body of water. According to Jackson, it was much larger than any current great lake, and its remains are seen in Lake Winnipeg, Lake in the Woods, and other smaller bodies. Some nine to eleven thousand years ago, the ice sheet which once covered a large swath of central North Central America dramatically receded, leaving immense amounts of water in its wake. Once part of a continental glacier, Hudson's Bay rapidly melted, opening up a new drainage basin that led to the drying up of Lake Agassiz. “It must have been insane”, Jackson said in wonder, picturing the experiences of the people who lived in these areas and would have seen such a changing environment in real time.

As the ice sheet covering today's Manitoban prairie receded, leftover water evaporated to a greater degree on the flatland than the wetter bedrock terrain to the east, forming the interlake plain divide we know today. History has not ended. As the climate changes, the juxtaposition between prairies and forest could become more stark. “We are on a breaking point of east and west”, said Jackson. He explained there is a school of scientific thought that believes the west will dry as the east becomes wetter, with the interlake plain acting as one boundary.

For those who haven't made the journey into the Manitoban prairies, or have yet to take note of the dramatic environmental evolution while doing so, I can only recommend you stop at the paradise village water park near Ste. Anne, not for amusement, but observation.