Humber River Marshes and Oak Savannah
Urban development, including the creation of grassy public parks, has left us few places to experience the Humber Valley in its natural state. You are now standing between two such places: a marsh and an oak savannah.
When humans first walked into the Toronto region as early as 11,000 years ago, they likely found a spruce parkland and open tundra landscape. The local climate and vegetation had changed by approximately 7000 years ago to resemble today's conditions, although the shoreline of Lake Ontario was about 500 metres south of its current location.
The marsh at the mouth of the river was first formed perhaps 5,000 years ago, when the water level of Lake Ontario approached its current elevation, and the Humber River slowed here to meet it. The marsh's wide range of plants, fish, waterfowl, and mammals made it a vital seasonal hunting, fishing, and gathering site for Aboriginal peoples.
Further up this path, a black oak savannah is a rare remnant of an ecosystem that once flourished around the lower Humber River area on the dry, sandy soils of the bottom of former Lake Iroquois (which preceded Lake Ontario 12,000 years ago). Oak, white pine, and sassafras trees grew in small groups across a savannah of grasses and low shrubs. This vegetation was subject to frequent fires, helping to maintain the ecosystem.
Though significantly reduced in size and altered by both the loss of some species and the introduction of others, the remnants of both the marsh and the oak savannah have survived pollution, landfill, residential development, a previous golf course, and the construction of the adjacent Humber Wastewater Treatment Plant. Efforts continue towards the protection and regeneration of these remnant native ecosystems.
Plaque via Alan L. Brown's site Toronto Plaques. Full page here.