Changing Forests in a Changing Climate

Ice on frozen branches

Our winters are getting warmer. Maybe you’ve been enjoying the milder weather or perhaps you’re pining for the colder days of winters past. If you find yourself in the latter camp, you’re not alone. Our local trees and forests rely on cold, consistent winter temperatures to stay healthy and resilient, and so do the insects and other wildlife that rely on trees for their survival.

Fluctuating winter temperatures caused by climate change produce intermittent freeze-thaw cycles and more frequent heavy rain events and ice storms. We also see earlier spring thaws, prolonged heat waves and droughts, and longer growing seasons. Most of the tree species in our local forests are adapted for historically colder weather conditions found in Ontario. As these conditions change, so will our forests.

Extreme weather events will cause more large-scale disturbances and destruction. Opportunistic invasive species such as Common Buckthorn and Garlic Mustard can colonize these disturbed areas, outcompeting native understory plants.

Invasive Garlic Mustard

Extreme summer heat and long periods of drought increase water transfer from the trees to the air (also known as evapotranspiration). This depletes trees of moisture. Under these conditions, trees focus on survival rather than putting out new growth and are unable to take advantage of longer growing seasons. Forest composition will change. Shorter-lived, faster-growing species will become more prominent and native coniferous species, like Hemlock, White Spruce and Tamarack, will decline.

Native White Spruce

The increased frequency of freeze-thaw cycles and milder winter temperatures also leads to greater browse damage by wildlife and early bud bursts. Premature bud growth can disrupt forest and wildlife synchronicity and prove fatal for some insects that rely on these buds for food.

Although we see these changes happening already, there are several actions landowners can take to protect our forests against climate change for future generations:

  1. Maintain healthy tree cover density by planting different native species.
  2. Promote tree age diversity by caring for older trees while allowing for new growth.
  3. Expand tree cover and build forest connectivity by planting trees to reduce fragmented forest patches.
  4. Properly manage plantation forests by thinning trees to improve growing conditions and promote the regeneration of native tree and shrub species.

Do you have a forest on your property or have questions about proper forest management? Contact us at [email protected] for more information.

By CVC’s Alastair Biscaia, Forest Management Technician

Comments (3)

  1. There is a high density development proposal (Orangeville Highlands) that will involve cutting mature trees, and encroaching on a significant wetland. There are butternut trees and mature forest in a Natural Heritage Woodlot that will be destroyed and disturbed if this development is allowed as is. This development will sit between Middle and Lower Monora Creek (coldwater streams to the Credit and Nottawasaga). We need CVC’s conservation voice more than ever. We are working hard as residents to protect our forest and water but we need CVC to recognize and protect Subwatershed 19 and high recharge areas such as this. Please CVC don’t leave this development as is, it will destroy a major wildlife and woodlot corridor to Island Lake. Please help.

    1. Hi Karen, thank you for your comments regarding the proposed development in Orangeville. CVC’s Planning and Development Services (PDS) staff review and provide comments on various Planning Act applications circulated to us by the municipality. Our role is to provide the Town with technical advice and coordinate any CVC regulatory matters through the planning process. If you wish to further discuss this proposal our Planning staff would be more than happy to assist. Please contact [email protected] for further information.

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