As a tree grows, carbon is stored in its leaves, branches, and trunk as well as in the surrounding soil. Trees use the carbon to produce sugars for tree growth then release oxygen back into the air. Without carbon dioxide, trees could not form the woody biomass that makes up their trunks and branches.
While growing, trees add a new ring of wood to their circumference every year. By weight this wood is about 50% carbon. Forests that absorb and store carbon over an extended period of time are considered carbon sinks.
Managed forests act as efficient carbon sinks as long as they are regenerated. Half a billion seedlings are planted in Canadian forests each year. Re-planting is the key reason why there has been no net deforestation in Ontario in the past 20 years, despite a long history of logging.
Carbon absorption slows down as trees mature. Eventually trees release carbon when they die. If the trees are harvested before they burn or decay, the carbon is stored indefinitely in the wood products. Planting trees begins the cycle again.
Trees grow most vigorously, rapidly absorbing and storing carbon, in the early to middle years. Growth slows as the tree matures. In unmanaged forests, trees eventually die and stop capturing carbon, but will continue to store carbon until they start to decay or are burned in a forest fire. Depending on the forest type and the ratio of young to old trees, this could translate into a net release of carbon over time.
When a tree is harvested, a small portion of the tree stays in the forest to decompose and the rest is removed and converted into forest products. Some carbon is released when the forest soil is disturbed during harvesting, and the roots, branches and leaves left behind release carbon as they decompose. But the majority of the carbon remains sequestered in the wood.
Numerically that means on average that .225 tonnes of carbon is stored for every cubic metre of round wood. Putting it into perspective, approximately five years of car emissions are sequestered in the wood frame of a typical home.
Once the harvested area of the forest is regenerated, the new trees once again begin to absorb and store carbon and start the cycle over again. This combination of harvest and re-growth, along with the benefit of wood products storing carbon for long periods of time, means that greenhouse gas emissions from harvesting practices are minimal.
Fighting Climate Change through Innovative Practices
Many of the effects of climate change can be reduced, delayed or avoided by sustainably managing our forests to boost their capacity to store carbon.
Ontario is working to increase the carbon stored in Crown forests by:
- Requiring the rapid replanting of new forests after harvest
- Accelerating growth rates by ensuring that tree species are planted on suitable sites and using seed from the best-quality trees
- Protecting forests from fire and insects where feasible
- Minimizing deforestation and planting trees in open areas, particularly in southern Ontario.
