storm belt

Mixedwood Plains

The Mixedwood Plains is the Canadian ecozone with the most southerly extent, covering all of southwestern Ontario, and parts of central and northeastern Ontario and southern Quebec along the Saint Lawrence River. It is the smallest ecozone in Canada, but it has become the country's most productive industrial and commercial region, and is home to nearly half of Canada's population, including its two largest cities, Toronto and Montreal.


The Mixedwood Plains essentially stretch along the Quebec City-Windsor corridor. At its western end, it encompasses all of Southwestern Ontario, and is bounded by three Great Lakes and its connecting waterways. To its north is Lake Huron, and to the south Lake Erie. Further east, it has boundaries with Lake Ontario to the south and Lake Simcoe to the north, before continuing east along a narrow strip of the Saint Lawrence River coast toward Quebec.

Striking physiographic features distinctly contrast the typically flat or gentle sloping ecozone, with the Niagara Escarpment being perhaps the most prominent. Once controlling levels of meltwater from glacial retreat during the last ice age, it now bifurcates the region from Niagara Falls to the northern tip of the Bruce Peninsula, then extends to Manitoulin Island.

In south-central Ontario, the ecologically important and politically sensitive Oak Ridges Moraine is a major feature of the Mixedwood Plains, with features such as rolling hills and the Happy Valley Forest representative of the ecozone. Due to the action of retreating glaciers, moraines are a common feature throughout this ecozone.

Some of the most fertile soil in Canada is located in this ecozone, in which the Holland Marsh has come to be known as "Ontario's vegetable basket", and the Niagara Peninsula is the most productive wine region in the country. Southwestern Ontario also represents the northern extent of the Carolinian forest, an important habitat for songbirds.

It covers a geographic area of 175,963 km².

It consists of one ecoprovince subdivided into four ecoregions: Saint Lawrence Lowlands, Frontenac Axis, Manitoulin-Lake Simcoe and the Lake Erie Lowland.

Protected areas

Within this ecozone are a number of protected areas. These include:


The climate of the Mixedwood Plains is characterised by warm to hot summers and cool winters. The Great Lakes and Saint Lawrence River have a significant moderating effect in this ecozone, which is in a major North American storm belt. Warm air fronts from the Gulf of Mexico and US south- and mid-west often collide with cold polar air masses, providing abundant precipitation in some areas. Annually, the region receives between 720 and 1,000 mm of rain and snow.

Summers average about 22°C in July in the southwestern end of the zone, and 18°C in the northeast. Winters are much milder in the southwest, with mean January temperatures dipping to -3°C, whereas mean lows are -12°C in the northeast.

Because of the relatively mild climate, the region has become an important and productive agricultural area. Agriculture has been the primary cause of deforestation in the ecozone; it was once covered entirely by forests. The resultant loss of natural habitat has caused a decline in the populations of many native species, and now over half of the Species at Risk in Canada are found in this zone.

Flora and fauna

The forests that remain in this zone still boast Canada's greatest diversity of tree species, among them white and red pine, oak, elm, maple and birch.


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