A new study published in the Journal of Sustainable Forestry. Carbon, Fossil Fuel, and Biodiversity Mitigation With Wood and Forests, confirms that building with wood really does reduce carbon dioxide emissions. A lot. And while we talk about how wood sequesters carbon for the life of the building, that is really the smallest part of it.
The real savings come from "avoided emissions"- a square meter of wood construction replaces a significant amount of concrete that would have been made to do the same job. For the first time that I know of, instead of just comparing the CO2 per cubic meter of building materials, it actually looks at the real world usage. Study co-author explains, in an article in The Conversation:
Building with wood consumes much less energy than using concrete or steel. For example, a wooden floor beam requires 80 megajoules (mj) of energy per square metre of floor space and emits 4kg CO2. By comparison, a square metre of floor space supported by a steel beam requires 516 mj and emits 40 kg of CO2, and a concrete slab floor requires 290 mj and emits 27kg of CO2.
Harvesting a bit more wood and using a lot less concrete could make a very big difference:
The 3.4 billion cubic meters of wood harvested each year accounts for only 20% of new annual growth. Increasing the wood harvest to 34% or more would have several profound and positive effects. Emissions amounting to 14-31% of global CO2 would be avoided by creating less steel and concrete, and by storing CO2 in the cell structure of wood products. A further 12-19% of annual global fossil fuel consumption would be saved, including savings from burning scrap wood and unsellable materials for energy.
The author also points out that sustainable forest management is good for forests, reduces the risk of forest fires, and creates jobs, which I would add don't involve cooking limestone with fossil fuels or digging big holes for aggregate. More at the Conversation