Linking Spruce Budworm Impacts to the Greenhouse Gas Cycle in Forests
Almost all grade-school children learn that trees absorb carbon-dioxide (CO2) and release oxygen (O2). I remember this lesson sticking the first time I heard it sometime in the 1980’s. I need oxygen and that comes from trees, therefore I need trees. Oxygen is still very important but in the time between the 1980s and today the conversation has shifted to the other side of the equation.
Forests absorb carbon dioxide and when they are healthy they do it on a very big scale. Trees store carbon in their roots, trunks, and crowns as they grow. The Canadian Forest Service estimates that for most of the 20th century, Canada’s managed forests were a massive carbon sink, significant at a global scale. However, large-scale natural disturbances like fires and insect outbreaks that cause forests to decline and die can swing the regional balance. The mountain pine beetle did this in western Canada and the spruce budworm has the potential to do so here in Acadian forests of the Maritimes.
Figure 1 – At the peak of a budworm outbreak, heavy defoliation can lead to greatly reduced capacity for trees to photosynthesize and take in carbon dioxide.
In an analysis led by Dr. Dave MacLean a figure has been placed on the potential greenhouse gas impacts of an uncontrolled budworm outbreak in the region. The result is sobering. The combination of expected growth loss (reduced capacity to absorb new atmospheric carbon) and tree mortality (release of carbon already stored) over a 25 year outbreak cycle in New Brunswick could result in an impact of 0.94* megatonne of carbon dioxide on average for each year of the outbreak.
At the peak of an uncontrolled outbreak, as reddish and grey trees become a common sight in our forests, the impact to greenhouse gas capture in New Brunswick is estimated to be as much as 2.8 megatonnes of carbon dioxide release each year. To put that into context, that’s about the same amount that is released today by the province’s largest industrial emission source: the coal-fired Belledune generating station or the equivalent of 14 million passenger vehicles driven for one year.
Through early intervention, the Healthy Forest Partnership is working to avoid those impacts entirely by keeping Atlantic forests growing and productive.
* 0.94 megatonne = 940,000 tonnes = 940,000,000 kg of CO2 each year on average, for 25 years.