Why Protecting Mature Pines in California Is Key to Fighting Climate Change Elsewhere
Marily Woodhouse, Director of the Battle Creek Alliance in Manton, is a staunch advocate for protecting old-growth forests and large trees in California. In her tireless efforts to preserve these ecological giants, she recently approached me to conduct a detailed analysis of Ponderosa pines as a usual timber source in her region. Her request stemmed from a critical need to support a presentation to the California Air Resources Board, where she planned to advocate for policies prioritizing the conservation of mature trees.
Let me share the report that is even more comprehensive than the article "WE CAN'T PLANT OUR WAY OUT OF THE CLIMATE CRISIS," which I co-authored with Bob Leverett. That analysis quantified carbon storage in red oaks of different sizes, answering the critical question: how many trees would need to be planted to replace the benefits of one large tree that was removed? Bob's data shocked the world and was featured globally, including in The Guardian.
This new report provides factual, actionable insights demonstrating the irreplaceable value of mature trees like Ponderosa pines in combating climate change.
In California, the largest known Ponderosa pine is the "Big Pine" in the Plumas National Forest, which measures 69.2 meters (227 feet) in height and 264 centimeters (104 inches) in DBH. The tallest known Ponderosa pine, named "Phalanx," stands at 81.77 meters (268 feet) and is located in the Myers Creek drainage of the Rogue River–Siskiyou National Forest in Oregon.
Why Mature Trees Matter More
Large trees are unparalleled in their contribution to climate change mitigation. The report, based on i-Tree Eco calculations, focused on selected ecosystem services provided by these trees, emphasizing three critical areas:
Carbon Storage: A single mature Ponderosa pine with a diameter of 104 inches stores 16,534.7 pounds of carbon. It would take over 16,000 smaller trees with a 1-inch diameter at breast height (DBH) to match this.
Cooling Effect: The evapotranspiration cooling potential of the same tree is equivalent to that provided by 781 smaller trees.
Carbon Sequestration: Annually, the tree sequesters 17.9 pounds of carbon—a contribution unmatched by 45 smaller trees combined.
These findings underscore the disproportionate ecological benefits of mature trees, reinforcing the concept of proforestation as championed by Professor William Moomaw. Proforestation focuses on allowing existing trees to grow to their ecological potential, maximizing carbon storage and ecosystem services over time.
Call to Action: Protect, Don’t Just Plant
The message of this report is clear: conserving existing mature trees is a far more effective and immediate strategy for combating climate change than planting new ones. Large trees like the Ponderosa pines in California's forests are ecological powerhouses, and their preservation should be a cornerstone of any environmental policy.
By embracing proforestation and prioritizing the conservation of mature trees, we can make a tangible impact in mitigating climate change and protecting the ecosystems that sustain us all.
From the report...
How Many Trees do I Have To Plant To Replace One Big Tree??
Carbon Storage & Sequestration And Cooling Effect Of Ponderosa Pines In California
Replacement Ratios for Carbon Storage:
A 104-inch DBH Ponderosa pine stores 16,534.7 pounds of carbon, equivalent to:
2 trees with 53-inch DBH
55 trees with 12-inch DBH
722 trees with 4-inch DBH
16,535 trees with 1-inch DBH
Replacement Ratios for Cooling Effect:
A 104-inch DBH tree provides 57.94 GJ of cooling annually, equivalent to:
2 trees with 53-inch DBH
10 trees with 12-inch DBH
90 trees with 4-inch DBH
781 trees with 1-inch DBH
Replacement Ratios for Annual Carbon Sequestration:
A 104-inch DBH tree sequesters 17.9 pounds of carbon annually, equivalent to:
2 trees with 53-inch DBH
7 trees with 4-inch DBH
45 trees with 1-inch DBH
Proforestation: A Key Strategy for Climate Change Mitigation
This analysis reinforces a critical truth: we cannot plant our way out of the climate crisis. While tree planting initiatives are valuable for long-term goals, the immediate and substantial benefits of conserving mature trees are irreplaceable. Large trees serve as carbon sinks, temperature regulators, and biodiversity havens, making them indispensable in any climate change mitigation strategy.
The concept of proforestation, as outlined by Bill Moomaw, prioritizes keeping large trees growing to maximize their ecological potential. Studies like the ones below from Frontiers in Forests and Global Change further emphasize that large-diameter trees store disproportionally massive amounts of carbon and contribute significantly to forest resilience and biodiversity.
Listen to a podcast where Bill Moomaw speaks about proforestation:
Studies Worth Knowing and Reading
Large Trees Dominate Carbon Storage in Forests East of the Cascade Crest in the United States Pacific Northwest.
Large-diameter trees store disproportionally massive amounts of carbon and are a major driver of carbon cycle dynamics in forests worldwide. In the temperate forests of the western United States, proposed changes to Forest Plans would significantly weaken protections for a large portion of trees greater than 53 cm (21 inches) in diameter (herein referred to as “large-diameter trees”) across 11.5 million acres (~4.7 million ha) of National Forest lands. This study is among the first to report how carbon storage in large trees and forest ecosystems would be affected by a proposed policy.
We examined the proportion of large-diameter trees on National Forest lands east of the Cascade Mountains crest in Oregon and Washington, their contribution to overall aboveground carbon (AGC) storage, and the potential reduction in carbon stocks resulting from widespread harvest. Analyzing forest inventory data from 3,335 plots, we found that large trees play a major role in the accumulated carbon stock of these forests. Tree AGC (kg) increases sharply with tree diameter at breast height (DBH; cm) among five dominant tree species.
Large trees accounted for 2.0 to 3.7% of all stems (DBH ≥ 1 inch or 2.54 cm) among five tree species but held 33 to 46% of the total AGC stored by each species. Pooled across the five dominant species, large trees accounted for 3% of the 636,520 trees occurring on the inventory plots but stored 42% of the total AGC. A recently proposed large-scale vegetation management project involving widespread harvest of large trees, mostly grand fir, would have removed ~44% of the AGC stored in these large-diameter trees, releasing a significant amount of carbon dioxide into the atmosphere.
Given the urgency of reducing atmospheric carbon and enhancing carbon accumulation to protect the climate system, it is prudent to continue protecting ecosystems with large trees for their carbon storage and co-benefits, including biodiversity habitats, resilience to drought and fire, and microclimate buffering under future climate extremes.
Mildrexler, D. J., Berner, L. T., Law, B. E., Birdsey, R. A., & Moomaw, W. R. (2020). Large Trees Dominate Carbon Storage in Forests East of the Cascade Crest in the United States Pacific Northwest. Frontiers in Forests and Global Change, 3. https://doi.org/10.3389/ffgc.2020.594274
Older Eastern White Pine Trees and Stands Accumulate Carbon for Many Decades and Maximize Cumulative Carbon.
Pre-settlement New England was heavily forested, with trees exceeding 2 m in diameter. Since farm abandonment, the forests have regrown, representing one of the most successful regional reforestation efforts globally and forming part of the “Global Safety Net.” Temperate "old-growth" forests and remnant stands demonstrate that native tree species can live for several hundred years, continuing to add to forest biomass and ecological complexity. Globally, forests are an essential natural climate solution, storing carbon and reducing annual increases in atmospheric CO₂ by approximately 30%.
While some studies emphasize the rapid growth of young forests, others highlight the carbon storage and accumulation potential of older trees. Using long-term, accurate field measurements and volume modeling of eastern white pines (Pinus strobus) in New England, this study examined carbon accumulation beyond 80 years and compared results to U.S. Forest Service models. Key findings include:
Intact eastern white pine forests accumulate above-ground carbon at high rates even beyond 80 years and can double stored carbon over subsequent decades.
Large trees dominate above-ground carbon storage and continue accumulating carbon for well over 150 years.
Productive stands maintain high carbon accumulation rates in live trees over long periods.
Given the urgency of addressing the climate emergency, maintaining and enhancing carbon in existing forests—proforestation—emerges as a powerful regional climate solution. New England forests, most of which are less than 100 years old, have tremendous potential for growth. Dedicating some forests to proforestation will produce large, carbon-dense trees while safeguarding biodiversity, special habitats, and ecosystem integrity. Strategically growing and protecting these forests represents a proven, low-cost natural climate solution with long-term benefits for biodiversity and climate mitigation.
Leverett, R. T., Masino, S. A., & Moomaw, W. R. (2021). Older Eastern White Pine Trees and Stands Accumulate Carbon for Many Decades and Maximize Cumulative Carbon. Frontiers in Forests and Global Change, 4. https://doi.org/10.3389/ffgc.2021.620450
Trees included in the report:
Tree No. | Tree species | DBH / inch | Heigh / feet |
|---|---|---|---|
1 | Ponderosa pine | 104 | 227 |
2 | Ponderosa pine | 53 | 100 |
3 | Ponderosa pine | 12 | 50 |
4 | Ponderosa pine | 6 | 40 |
5 | Ponderosa pine | 4 | 25 |
6 | Ponderosa pine | 2 | 10 |
7 | Ponderosa pine | 1 | 4,5 |
Graphical Insights
To visualize these findings, download the figures from the gallery:
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