The Carbon Cycle in Forest Ecosystems

Our forests are one of the greatest resources for mitigating the impacts of climate change. A key benefit our forests provide is their ability to remove carbon in the atmosphere and store it in their trunks and root systems, as well as the soil.

A common misconception is that younger forests are better at sequestering carbon than older forests, and therefore better for mitigating climate change. This doesn’t accurately portray the role forests play in sequestering and storing carbon.

As illustrated above, older forests sequester carbon at a slower rate than younger forests, but they store significantly more carbon. The longer carbon is stored, the more forests are able to mitigate climate change. In fact, leaving forests in tact is our greatest natural climate solution for limiting the impacts of climate change.

Another misconception is that harvesting trees on shorter rotations will sequester and store more carbon because another young forest will be planted that sequesters carbon at a fast rate. But this argument fails to account for the significant carbon that is released from timber harvest: the unused parts of the tree which are burned or decay rather than becoming wood products. Additionally, carbon storage in wood products is temporary. A study found that 81% of carbon removed from west coast forests since 1900 has been released to the atmosphere or deposited in landfills (Hudiburg, 2019).

Shorter logging rotations play a role in supplying timber products. However, harvesting trees at 40 or 50 years does not allow forests to reach their maximum growth potential or optimize other valuable benefits. Short rotations and clearcutting limit the capacity of the ecosystem to produce clean air and water, provide habitat for wildlife, and store carbon.

Although forests are critical for carbon sequestration and storage (as well as other ecological and social benefits), they also provide important timber products that we rely upon. The debate is often framed as whether to harvest forests for timber or conserve them for ecological benefits, but we can manage forests strategically to provide both public benefits and timber products.

Opportunities to Manage State Trust Lands for Multiple Benefits: Mature Forests

There are many options to shift management of forests on state lands to improve forest health, store carbon, ensure clean air and freshwater while continuing to supply wood products.

The CNW v. Franz ruling affirmed DNR has a broad mandate and discretion in managing these lands for the public and for beneficiaries. Unfortunately, DNR has not seized the opportunity provided by the court’s ruling and has maintained forest management and harvest using its outdated agronomic model.

This outdated model includes harvesting many of the last remaining acres of mature and carbon dense forests (sometimes referred to as legacy forests) on DNR trust lands. These mature forests have begun to develop more characteristics of an ecologically healthy forest and as a result provide far more ecological benefits, including carbon storage. Once cut, these forests release vast amounts of carbon and cannot regenerate in a human lifespan.

Despite claims from the timber industry, the forest products from harvest of these mature trees do not store as much carbon as an intact mature forest.

Environmental groups, community members, and elected leaders across Washington have organized to halt timber sales and protect these mature forests from DNR harvest. This movement makes clear that the public expects different management practices and benefits from trust lands.

Conserving the structurally complex, carbon dense, mature forests on DNR trust lands is only one step towards improving forest management for the benefit of all Washingtonians. Multiple strategies are needed to meet multiple goals. Lengthening the decades a forest is allowed to grow before it’s harvested for timber products also plays a major role in improving carbon storage and sustaining rural economies.

Opportunities to Manage Trust Lands for Multiple Benefits: Extended Rotations

It is possible to increase the carbon storage and sequestration of forests while sustaining timber supply in Western Washington. A small portion of trust lands contain remnant, mature forest of significant conservation value, which generate the most value if they are conserved. Beyond these irreplaceable areas, the needs of Washingtonians can be better served by shifting to climate-smart, ecological forest management practices like extended rotations, uneven aged stands, and protection of riparian areas, which can help improve carbon storage.

A study conducted by Conservation Northwest and Washington Conservation Action in conjunction with Resilient Forestry modeled the carbon and timber volume impacts of transitioning to extended rotations across the forested landscape. The study showed that it is possible to transition to 80-year rotations between harvests and conserve older existing stands while maintaining comparable flow of timber to mills, and increasing carbon storage compared to current, shorter rotations.

Of the approximately 2.1 million acres DNR manages, about 700,000 are designated General Ecological Management (GEM) lands, which are primarily for short rotation logging and beneficiary revenue. The average age at harvest on GEM lands is 48 years. By shifting the average stand age to 80 years of age over a 70-year period, those forests would absorb an additional 32 million metric tons of carbon. Managing forests for extended rotations can provide greater ecological benefit, continued supply of timber, and generate more local employment in the forest sector.

For more information on how extended rotations can improve carbon sequestration please see this link from our partners at Conservation Northwest

DNR has full authority to evolve management on trust lands to fulfill the agency’s mandate: provide beneficiary benefit alongside public benefit. Existing tools can help DNR make this transition in a way that is good for communities and the environment, including carbon offset projects, and Climate Commitment Act investment funds.