How to Calculate the Wood Carbon Footprint of a Building

Expanding the possibilities of wood building design
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Sponsored by Think Wood
By Edie Sonne Hall, Ph.D.

The Forest Side of the Equation

Responsibly managing forests in a way that balances harvesting and replanting, and provides a sustainable source of wood products that continue to store carbon and offset the use of fossil fuels, can significantly reduce the amount of carbon in the atmosphere over the long term.

The U.S. Forest Service (USFS) keeps track of the volume and health of U.S. forests by measuring permanent plots scattered across the country through its Forest Inventory Analysis (FIA) program (www.fia.fs.fed.us). These measurements are rolled up into the national GHG inventory that is reported to the IPCC every year as part of the U.S. commitment under United Nations Framework on Climate Change. In 2018, U.S. forests and harvested wood products were a net sink on the order of 663 million metric tons CO2e, which offsets about 10 percent of the nation’s GHG emissions.22

The FIA program can also provide information about trends on different forest ownership and types, as well as impacts of growth, mortality, and harvest in different regions over time. For example, the amount of forest area has remained constant since about 1900, and U.S. forests have been net sequesterers since the 1950s. During this same period, harvests have remained stable or have increased in some cases, such as in the U.S. South.23

Every 10 years, the USFS reports on the state of the U.S. forests as well as future projections through the Resources Planning Act mandate, established by the Forest and Rangeland Renewable Resources Planning Act of 1974. The most recent report found the following highlights:24

  • Forest and woodland area in the United States has plateaued at 823 million acres following decades of expansion. Forest land area alone occupies 766 million acres. Together, forest and woodlands comprise more than one-third of the U.S. landscape and contain 1 trillion cubic feet of wood volume—enough wood to fill the Great Pyramid of Giza 12,000 times.
  • Forest industry in the United States makes up 17 percent of global roundwood production, and the nation has the highest intensity of industrial roundwood consumption per capita. The impact of the 2007 recession on wood product demand is still reflected in inventory data, with a 19 percent decline in Southern timber removals between 2006 and 2016. However, that trend should reverse as housing markets continue to recover.
  • While forest land is becoming more accessible to people and 67 percent of forest land is legally available for harvest activities, tree cutting and removal occurs on less than 2 percent of forest land per year. Contrast that with the nearly 3 percent disturbed annually by natural events like insects, disease, and fire.
  • Wildfire, insects, and disease are among the biggest threats to forests and woodlands in the nation. Low harvest rates, aging forests, mortality from insect and disease infestations, and extreme weather events have combined to create conditions that facilitate wildfire.

Changing environmental conditions have made the active management of forests critical. For example, wildfire is a natural and inherent part of the forest cycle. Today, however, wildfires must be prevented from burning unchecked because of danger to human life and property. As a result, many forests have become over-mature and overly dense with excess debris, which, combined with more extreme weather, has caused an increase in both the number and severity of wildfires.

The combination of older forests and changing climate is also having an impact on insects and disease, causing unprecedented outbreaks, such as the mountain pine beetle, which further add to the fire risk. Active forest management, which includes thinning overly dense forests to reduce the severity of wildfires, helps to ensure that forests store more carbon than they release. Forest management activities aimed at accelerating forest growth also have the potential to increase the amount of carbon absorbed from the atmosphere.

The Canadian Forest Service also tracks the health and productivity of Canada’s forests. Canada is the third-most forested country in the world with 857 million acres forest with low levels of land-use change, just like in the United States. Only 0.3 percent of standing wood volume and less than half of 1 percent of land area was harvested in 2017. Disturbances have a much larger impact on Canada’s forest area and inventory, impacting almost three times the area that was harvested in 2017.25

 

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Originally published in Architectural Record
Originally published in September 2020

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