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Forest Carbon: Glossary of Key Terms and Rules of Thumb

Foresters often hear non-foresters confuse terms, such as referring to lumber as timber or logs (which is like calling a pork chop a pig). A confusion with terms leads to misunderstanding issues and ultimately complicates analysis or discussion intended to improve understanding and support decisions. To quote Voltaire: “If you wish to converse with me, define your terms.”

Forest carbon, and carbon markets generally, provide amble opportunities for misunderstanding. Carbon policies, prices and measurements mean different things to different people across different programs with different rules and definitions.  So, let’s define a partial set of terms and share a few basic metrics to strengthen our common understanding of forest carbon concepts.

Carbon 101 Terms

Carbon is a nonmetallic chemical (atomic number 6!) found in its impure form in soot and coal. Carbon dioxide(CO2) is a chemical compound that exists in our atmosphere; burning fossil fuels for power or cars are primary man-made sources of CO2. Forest carbon generally refers to the carbon dioxide absorbed from the atmosphere by trees as they grow.

Carbon Sequestration 101

Carbon sequestration refers to removing carbon dioxide from the atmosphere and storing it in a carbon sink such as forests, the ocean or another natural or man-made system or product. In this context, sequestration refers to any process that captures and stores carbon.

Forest Carbon Offsets 101

Markets have evolved for three forestry-related approaches to carbon offset projects. Afforestation (or reforestation) projects involve restoring tree cover to previously non-forested land. Avoided conversion projects prevent the conversion of forested land to non-forested land. Finally, improved forest management (IFM) projects include land management activities that increase (or maintain) current levels of carbon stocking.

Meaningful forest carbon projects have important attributes. One is additionality, which requires the forest project sequester more carbon than what would have happened in a “business as usual” (aka baseline) scenario.

Forest Carbon Context: Rules of Thumb

In forestry, I always found rules of thumb helpful in providing context.[1] A few numbers may help us wrap our minds around carbon markets, as well. According to The Nature Conservancy, the average annual carbon “footprint” per person in the U.S. is 16 tons (versus the global average of ~4 tons).

How much is that? We turn to the EPA’s Greenhouse Gas Equivalencies Calculator to provide some context. In the United States, a family with two passenger vehicles would generate 9.2 metric tons of emissions per year (based on 1,035 gallons of gas consumed). Offsetting this requires 152 seedlings grown for 10 years or 11.2 acres of mature forests growing for one year. So, we’re talking 5 to 6 acres of forest growth for one year per car per year.[2]


This post is the first in a series related to the Q3 2021 Forisk Research Quarterly (FRQ). To further address this topic, Forisk’s 5th annual “Wood Flows and Cash Flows” conference on September 2nd, 2021 includes a session on forest carbon. To learn more and to register, click here.


[1] For example, a log truck in the U.S. South carries just over 25 tons (~28) of wood and a sawmill needs about 4 tons of logs to produce one thousand board feet (1 MBF) of softwood lumber. Also, according to NCX (formerly SilviaTerra, one harvest deferral credit in their forest carbon program is approximately one truck load of logs.

[2] Offsetting 1 million metric tons of carbon dioxide means taking over 217,000 cars off the road for a year or 16.5 million seedlings grown for a year. It’s also the same as preventing 6,837 acres of forest from conversion to non-forests. For reference, there were over 276 million motor vehicles registered in the U.S. as of 2019 (https://www.bts.gov/content/number-us-aircraft-vehicles-vessels-and-other-conveyances).

Comments (2)

  1. Jim Rinehart / Reply

    In the world of marketable offsets, it is of course important to note that for the offset to have value as such, it must represent growth that would not have occurred otherwise. Additionality is the trick. Otherwise it’s just slight of hand.

  2. Will Sonnenfeld / Reply

    Right you are, Jim. Permanence is another key, something a one-year harvest deferral does not accomplish. And to round out the trio of keys, a legitimate carbon sequestration (capture + storage) strategy has to avoid “leakage.” If a reduction in harvesting is simply met by an increase somewhere else, or if concrete or steel (which emit more carbon than wood) replaces wood in construction, then the carbon sequestration effort has failed. To summarize, there are three keys to assessing the quality of a carbon sequestration strategy: Additionality, Permanence, Avoided Leakage.

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