Greenhouse gas (GHG) emissions are a measure of forest health and its relationship to climate change. Positive emission scores indicate the forest is a source of GHGs and negative emission scores indicate that the forest is a sink for GHGs. If the forest acts as a GHG sink, it is healthy and growing. If the forest is acting as a source of GHG emissions, it may be over-mature, dying and in decay.
What we are doing
The National Forest Carbon Monitoring, Accounting and Reporting System estimates forest carbon stocks, changes in carbon stocks and emissions of greenhouse gases in managed land and forests. These estimates are based on data from Saskatchewan's forest inventories, growth and yield tables, disturbance monitoring and management activities. The ministry monitors the rate of change in carbon stock and emissions in the forest ecosystem using the federal carbon budget model.
The forest ecosystem contains carbon stock which includes above-ground biomass (i.e. trees), below-ground biomass (i.e. live roots), deadwood, litter and organic soil matter. Carbon quantities change over time due to tree growth, which adds to the carbon stock. Losses from carbon stock occur through decomposition, natural disturbances (e.g. wildfire and insects) and forest harvesting. Forest carbon storage is the total amount of carbon contained in all the components of the forest ecosystem at a given time. This analysis is only representative of the managed forests in Saskatchewan and does not include the far northern part of the provincial forest. There are few human activities in the far north and a general lack of information on forest carbon in this part of the province.
Saskatchewan's managed forests have been a relatively small greenhouse gas sink, averaging net stocks of 0.50 megatonnes annually. Forest greenhouse gas emissions come from physical disturbances which include harvesting and land use changes (not a significant factor in Saskatchewan), as well as natural processes such as growth and decay. Significant natural disturbances such as wildfire, insects and disease are not included in this analysis of greenhouse gas emissions. As indicated in two graphs above, depending on the accounting system used, Saskatchewan's forests could be considered a small source or a small sink.
Harvested wood products, including the use and disposal of products (e.g. paper, lumber, etc.), and forest conversion activities are considered a source of emissions. This is consistent with the reporting criteria established by the United Nations Framework Convention on Climate Change. For more information on how greenhouse gas sources and carbon sinks are calculated for forests in Canada, visit the Government of Canada.
Why it matters
A forest is considered to be a carbon sink if it absorbs more carbon from the atmosphere than it releases. The forest stores a significant amount of greenhouse gases in the form of carbon, the building blocks of plants and trees. An increase in stored, or sequestered, forest carbon can indicate a healthy forest in which the growth exceeds the loss of carbon to human and natural disturbances. Over-mature forests become sources of emissions as they start to die and decay. Managing forest age through sustainable planning and harvest practices is an important part of emissions management.
Carbon in the form of trees provides the raw material for the forest industry. Healthy forests that sequester carbon also provide a sustainable supply for the forest industry. In Saskatchewan, timber harvest levels are well below the sustainable limit, which means that carbon stocks are not impacted by this type of disturbance.
Managing the provincial forest to balance growth while maximizing a sustainable harvest is an important part of mitigating climate change. Death and decay can reach the point where wood supplies and the quality of trees begin to decline, making harvest and commercial utilization unsustainable. Low timber harvest levels can also contribute to aging forests.
Underutilized, aging forests are vulnerable to fire, insects and disease. Across Canada, the area burned by forest fires is expected to double by the end of the century, releasing large quantities of carbon. Changes to temperature and moisture can contribute to damage from insect and disease and impact forest growth rates. These variables all impact the forest's ability to be a significant carbon sink over time. Visit Natural Resources Canada for more information.