As part of the carbon cycle, wood biodegradation releases carbon that was consumed during tree growth back into the atmosphere. Delaying this release is one of the ways wood products help to sequester carbon and combat climate change.
Wood is primarily biodegraded by decay fungi and insects, such as termites. These agents of biodegradation are also impacted by climate change.
Decay Fungi
Wood decay fungi are ever-present in most parts of Canada. Their growth and consumption of unprotected wood is largely controlled by moisture and temperature, both of which are impacted by climate change. The decay hazard for a region is broadly influenced by the time that the wood is warm enough and wet enough to support fungal growth. Decay fungi grow above freezing and above fibre saturation, with optimum conditions ranging from 21 to 32°C and 40 to 80% moisture. The National Building Code of Canada requires the use of wood treated to the CAN/CSA-O80.1 standard to be used in applications not protected from exposure to precipitation where the moisture index is greater than 1.00 and the configuration is conducive to decay, such as beams extending beyond roof decks, junctions between deck members, and connections between balcony guards and walls. Climate change will impact moisture indices with associated decay hazards increasing or decreasing in different regions.
FPInnovations’ field-testing program, supported by Natural Resources Canada, generates long-term performance data on durable wood products. Much of this research is focused on understanding the efficacy of various wood protection technologies. However, the data also provide a baseline to help understand the impacts of a changing climate on wood product performance. Wood product field performance at test sites in British Columbia, Ontario and Quebec has been documented over the last several decades. Long-term access to these sites enables performance to be evaluated under changing climatic conditions. Proven performance at multiple sites provides confidence that naturally durable woods and wood protection technologies will perform as intended under the climates of the future.
FPInnovations’ field performance data was recently used as part of an international initiative to model the decay resistance of various woods. Data from test sites around the world were used to determine material-specific resistance dose values, which were correlated to decay rates. These models are now being used by collaborators to develop digital tools that will help specifiers select the appropriate wood protection technologies for the exposure conditions and required service lives of their project.
Some of FPInnovations’ long-term above-ground decay tests, Petawawa Research Forest, Ontario.
Termites
Subterranean termites that attack wood structures are largely confined to parts of southern Ontario and southern British Columbia. Their northward expansion is primarily limited by cool temperatures. Warmer temperatures may enable them to increase their range in Canada. The National Building Code of Canada requires wood treated to CAN/CSA O80.1 standards to be used in areas with termite hazards unless clearance from the ground is more than 450 mm and visible for inspection. Climate change increases the risk of termites expanding their range, and the intensifying activity where they are already present.
Wood structures can be protected from termites by a variety of technologies including site management, baiting, soil treatments, slab and foundation detailing, physical barriers, and inspection. The last line of defense is to use durable wood products that protect against termites, such as preservative treated wood. FPInnovations’ test site in Kincardine, Ontario is in a termite hazard zone. In a recent study on wood posts, decay and termites led to rapid failure in untreated red pine while preservative-treated pine resisted attack. This test site enables the efficacy of wood preservative technologies against termites to be measured. These technologies are expected to have increased importance for wood product performance as termite hazards increase.
Proven protection technologies that provide long and predictable service life are an important tool to realize the carbon sequestration benefits of wood products.
To learn more about wood protection:
- How does FPInnovations help prevent alien invasions?
- Building enclosure and moisture management of mass timber construction
