sources and sinks of carbon
Biosphere Daily Earth Science Environment Repost

When forests burn: Sources and sinks for carbon

Forests cover 33 percent of the United States, occupying about 750 million acres. They are simultaneously serving as both sources and sinks for carbon dioxide (CO2) because they emit CO2 when burned and store it when they grow.  So, when forests burn, they release tremendous amounts of CO2 into the atmosphere. But climate change is causing increases in both the frequency and intensity of wildfires, and these wildfire problems are shedding light on decades of forest mismanagement. 

The U.S. Forest Service calculates that forests sequester about one-sixth of the country’s annual CO2 emissions. But gains in sequestration are sometimes offset by greenhouse gas emissions from forest fires. On a global scale, wildfires emit about 8 billion tons of CO2 annually. This occurs against a backdrop where total global CO2 emissions in 2019 were 33 billion tons. So, at first glance, forest fires account for 25% of all carbon emissions. However, their real contribution is lower due to regrowth in the burned areas.

The environmental toll of large forest fires is significant. California wildfires alone released 68 million tons of CO2 into the atmosphere during 2018. These fires accounted for 15 percent (approximately one-sixth) of the State’s total emissions that year. Because of the wildfires, the State’s forests were carbon neutral, sequestering as much CO2 as they released.  

Forest management is at the heart of dealing with wildfires, but the debate on how to manage our forests spills over into the realm of renewable energy. 

Biomass Energy

The U.S Energy Information Administration (EIA) divides renewable energy into five categories: biomass, hydropower, geothermal, wind, and solar. These all represent energy sources that are naturally replenishing. But renewable energy is not necessarily clean energy. Wood is part of the renewable biomass category, yet burning wood releases greenhouse gases into the atmosphere. Additionally, wood is a dirty fuel source, releasing one and a half times more carbon than coal.

Biomass fuel projects are controversial. When Europe opened the way for biomass power plants, the production of wood pellets doubled in some areas of the U.S. southeast. Large scale logging to fill the wood-demand saw the disappearance of 35 million acres of natural forests. Yes, these forests underwent replanting, but with monoculture stands of pine that don’t support the regional ecosystems. Local species extinctions have doubled because of the way commercial logging is managed.

The western U.S. also faces controversies around biomass energy versus forest management. Decades of forest management through fire suppression, have taken a toll. Today, forests choked with dead trees, and thick undergrowth, provide the ideal setting for large, intense forest fires. When this tinderbox environment combines with an ongoing megadrought in the American West, the result is explosive wildfires. Hotter temperatures and longer dry seasons turn these fuel-choked forests into disasters like the Camp Fire of 2018, which destroyed the town of Paradise. 

California has also lost 147 million trees since 2013 from bark-beetle infestations. This deadwood and copious amounts of small trees and undergrowth are the fuel that wildfires thrive on, and efforts are underway to thin the forests by harvesting deadwood and undergrowth trees for biomass energy. The conundrum is that harvesting reduces wildfire frequency and size, but biomass burning uses a dirty fuel source, releasing lots of carbon.

Thinking of ecosystems versus only thinking of trees

Forests are a vital ecological resource, but managing them and balancing their simultaneous roles as sources and sinks of carbon is difficult. Trade-offs are inevitable as we look for ways to reduce the impacts of climate change, and choices are sometimes limited to the lesser of two evils. However, there are legitimate guideposts to gauge the impact of our actions.

Ecosystem preservation is one of these guideposts, and it is measured by species diversity. Clear-cutting, followed by mono-species planting, is a common forest management practice.  But this practice is also a blow to biodiversity and a poor way to manage our forest resources. Restoring ecosystems should be the required outcome after logging, not simply planting trees. 

Forest health is another guidepost. Wildfires are one of nature’s methods of thinning forests. However, human encroachment into the forests creates a need for fire suppression, but this encourages intense, dangerous fires when they do occur. Managed thinning of the forests is one solution to maintain healthier woodlands. Disposal of culled trees is a problem created by thinning, and using this wood as biomass fuel is one disposal solution. But perhaps there are more environmentally friendly solutions. Regulation, economics, and innovation all play a part in finding long-term solutions. 

Forest science matters

Meaningful regulation and thoughtful innovation both need guidance from good forest science. Unfortunately, decisions based on science are increasingly shunned by our elected leaders. Maximizing immediate economic gains appears more important than a sound policy that preserves our natural resources and makes them truly sustainable.

The rise of tree-planting as a primary solution to climate change exemplifies a lack of scientific understanding. Forests have a positive role in carbon sequestration and climate change management. However, tree planting as a solution to global warming is not a real plan. Instead, it is a political talking point to avoid making actual policy addressing climate change. Our forests are sources and sinks of carbon, and without proper management, tree planting may eventually release more carbon than it sequesters.

Managing ecosystems is much more than planting trees and policies addressing climate change should seek to preserve our ecosystems.


Forests as a pathway for terrestrial carbon sequestration (Source: ArcheanWeb) –  Also:

Tree planting as a carbon sequestration plan (Source: ArcheanWeb) –  Also:

Tongass National Forest: The good, the better, and the beautiful (Source: ArcheanWeb) – Also:

When do forests become a carbon liability? (Source: ArcheanWeb) – Also:


How Wildfires Can Affect Climate Change (and Vice Versa) (By BOB BERWYN; INSIDECLIMATE NEWS) –  Also:

Global CO2 emissions in 2019 (Source IEA) –  Also:

New Analysis Shows 2018 California Wildfires Emitted as Much Carbon Dioxide as an Entire Year’s Worth of Electricity (Source: U.S. Department of the Interior) – Also:

The Debate Over Burning Dead Trees to Create Biomass Energy (By Jane Braxton Little; Wired) – Also:

Feature Image: Epping Forest High Beach Essex England (Modified) – By Acabashi – Own work, CC BY-SA 4.0,  

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.