Why forests need fires, insects and diseases

A pine tree grows after a forest fire. Although natural disturbances do create a temporary loss in the forest cover, in the long term they help forests stay healthy and encourage diversity in the tree, plant and animal species that inhabit them.

How do natural disturbances affect Canada’s forests?

Natural disturbances such as forest fires, insect and disease outbreaks, drought, wind throw and floods have occurred in Canada’s forests for thousands of years. Disturbance is part of the natural life cycle of the forest and most often helps the forest to renew itself.

Disturbances are particularly important to the cycle of regeneration and regrowth in boreal forests. Fires, as well as insect and disease outbreaks, often occur on a large scale there, more so than in Canada’s temperate forests. Here are some of the ways that these natural disturbances work to renew boreal forests.

Forest fires often stimulate new growth

Fire, the primary change agent in the boreal zone, is as crucial to forest renewal as the sun and rain. Forest fires release valuable nutrients stored in the litter on the forest floor. They open the forest canopy to sunlight, which stimulates new growth. They allow some tree species, like lodgepole and jack pine, to reproduce, opening their cones and freeing their seeds. Learn more about the effects of wildfire in the forest.

Insects reduce aging trees and make the forest more productive

Insects are important in the life cycle of boreal forests. Large insect outbreaks that occur regularly help to renew the forests. Insects release nutrients stored within trees. Infestations also eliminate sick and aging trees, reducing competition among trees and making the ecosystem more productive. Find out about the insects that affect forests in Canada.

Diseases eliminate weak trees and give new species a chance to thrive

Diseases contribute to the forest ecosystem by speeding up the mortality of weak and over-mature trees, clearing the way for forest renewal and increasing biodiversity. Diseases also break down dead plant material, a process that recycles nutrients and organic matter. Root diseases are among the most common in boreal forests. Read about the ways diseases impact Canadian forests.

Canada closely monitors and reports on natural disturbances

Although natural disturbances generally benefit the long-term health of Canadian forests, they can sometimes have public safety and environmental consequences. Canada closely monitors disturbances in its forests and reports publicly on their effects. The annual State of the Forest report includes the latest information on key disturbances such as fire, insects and disease. The government also makes a number of tools available to the public, such as maps to monitor forest fire conditions in Canada and databases of insects and diseases in Canada’s forests.

Natural Resources Canada–Canadian Forest Service scientists conduct extensive research and analysis on natural disturbance in Canada’s forests. Their reports are used to inform forest management planning, forest laws and forestry practices. For example, scientific research has helped evolve modern harvesting techniques to more closely mimic the effects of natural disturbance on the forest.

Although forest fires, insects and diseases do temporarily reduce the forest area, it’s important to remember that the trees will almost always grow back. Natural disturbance should not be confused with deforestation. A forest that will grow back is still a forest.

Learn the difference between natural disturbances and deforestation

Natural disturbances like wildfire or disease are often mistakenly thought to cause deforestation. Find out why this is untrue when you read these 7 reasons why disturbances don't cause deforestation.

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