Although not like it was 200 years ago, the Humber is adapting. Work is needed to support appropriate tree species, and limit invasive species, but the valley again has abundant wildlife with deer and mink, with salmon and trout in the river.
Several weirs were built largely to control the sea lamprey they the St. Lawrence Seaway introduced. http://www.invadingspecies.com/invaders/fish/sea-lamprey/
Toronto Region Conservation Authority later built fish ladders to bypass the weirs, and stocked the Humber with several species of trout and salmon. There is now fly fishing in Mount Dennis, with fish a metre long caught regularly. And critically, the fish are spawning and returning to the Humber!
Many invasive species, especially Manitoba Maple, have established themselves. One of the goals of the trail is to remove the invasive and unwanted growth, and plant more desirable species appropriate for a Carolinian forest.