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The Substitution Effect – how forests work for the climate

By June 30, 2023July 4th, 2023No Comments

How does forestry help reduce emissions? We spoke with Peter Holmgren, PhD in forest management, who explains the climate benefits when forest products replace fossil products.

The climate benefits of forests need to be understood from two perspectives. It’s not enough to just look at the forest’s capacity to absorb carbon dioxide from the atmosphere through photosynthesis. From a climate perspective, it’s also important to look at the benefits of storage and substitution. Storage refers to the amount of carbon sequestered in wood products, and substitution refers to how much these products reduce the use of fossil material.

When a forest is harvested, the amount of carbon previously absorbed by the growing trees is stored in the products that are made from the wood. These may be long-life building materials, or short-life paper packaging or energy production that provide a relatively short-term storage effect.

But forests also provide major climate benefits when forest-based products replace products made from fossil-based material. Here, emissions of fossil carbon dioxide are replaced by emissions of biogenic carbon dioxide. As long as only the net growth of the forest is used to produce forest raw material, the level of carbon dioxide in the atmosphere does not increase. Peter refers to the reduction of fossil emissions as the “main job”.

“The debate about forests and the climate often focuses on the forest per se, but climate action involves two very distinct objectives. One is to reduce fossil emissions, and this is the main job. The other is to ensure and increase carbon sinks in the biological system.”

There is a perception that the best climate benefit would be achieved by leaving forests alone. Peter dismisses this idea and maintains that it is important to view the forest as a biological, circular system where we harvest less than we grow.

“From this circular system we gain renewable raw materials, and we can also use these raw materials to eliminate fossil emissions.”

Peter also stresses the importance of maintaining a time perspective. The achievement of climate goals is indeed an urgent matter, but the idea that we need to bind carbon in the forest as soon as possible has two side effects. Firstly, it actually increases the amount of fossil emissions. Secondly, forestry extends over a much longer period than that covered by today’s climate goals. The forest’s climate work will continue far beyond 2030 and 2050.