Cutting Down Forests Releases Green House Gases

Eucalyptus forests are exceptionally good at sequestering carbon: They’re big and fast-growing, with dense wood and long lives. The forests store even more carbon in the soil, much of it in the top three feet. This is true of Sutro Forest, of Mt Davidson, of the forested areas of Sharp Park and McLaren Park and Bayview Hill, the forests on Yerba Buena island. All these forests are threatened, and the people who want to cut them down have understated the expected release of carbon once the trees are cut down, the soil churned up, and the chipped trees left to decay.

The article below is specifically about such understatements in UCSF’s Draft Environmental Impact Report for the Sutro Forest Management Plan (that starts with cutting down 6,000 trees in Phase I). But it’s the same story in all the other forests we mentioned: The carbon impacts are ignored or minimized with bad data.

This article is reprinted with permission from, a website that advocates for Sutro Forest.

Sutro Forest is an excellent carbon sink: The eucalyptus trees are tall, fast growing and have dense wood. In some parts of the forest, the mid-story of blackwood acacia boosts this carbon storage as well. The understory is lush and evergreen. The forest floor is damp most of the time. It’s practically the perfect carbon forest. It’s also a special ecosystem and excellent wildlife  habitat.

Disturbing this forest is going to release Green House Gases (GHG), and the Sutro Forest DEIR (where the deadline for comments closed on September 22nd) underestimates how much. Here, we publish with permission the comment from Eric Brooks. He’s the Sustainability Chair, San Francisco Green Party and Campaign Coordinator, Our City SF. [Please note: all the photographs in this article are ours and not part of the comment sent to UCSF.]


Comments To: Draft Environmental Impact Report (Draft EIR) – UCSF Mount Sutro Open Space Reserve Vegetation Management Plan

Fundamental GHG Calculation Flaws & Neglect of Wildlife Habitat Retention Strategy

To all concerned with the Draft Environmental Impact Report for the UCSF Mount Sutro Open Space Reserve Vegetation Management Plan,

I write to raise very serious concerns about very fundamental and deep flaws in the Draft EIR (DEIR) assessment of greenhouse gas emissions from the proposed project and related wildlife habitat impacts.

The assessment has key and deep flaws in its methodology for greenhouse gas assessment, and must be fundamentally changed, and the assessment completely redone.

1) The first deep flaw in the methodology and assessment is the assumption on page 4.7-3 that:

“Forest‐soil carbon is a large, stable pool, accounting for some 50 percent of the total forest carbon and changing very slowly over hundreds of years (Kimmins 1997). For timeframes of 100 years and less, forest accounting can ignore this pool and focus on changes to more labile forest carbon components (i.e., trees, understory, litter).”

This assumption is simply not correct and completely ignores the fact that when forest soils become both disturbed and more exposed to the elements, due to tree and vegetation removal, vast amounts of carbon in the form of CO2 and methane are released *from* the soil. The greenhouse gas emissions calculations and assessment must therefore be completely redone to include soil carbon losses in the calculations.

2) The second deep fundamental flaw in the DEIR greenhouse gas assessment is its reliance on the Significance Criteria under section 4.7.5 on page 4.7-10

This criteria is solely an arbitrary emissions cap and is the wrong criteria. The only proper criteria by which to assess greenhouse gas emissions of a forest is to compare its net carbon sequestration and emissions before disturbance, to its net sequestration and emissions after disturbance, in order to make a comprehensive assessment of its full internal net sequestration and emissions impacts – including all soil impacts and carbon losses and sequestration. It is the percentage net increase of greenhouse gas emissions in any given forest that matter, not an arbitrary cap on a specific emissions number which is not related to the full carbon cycle of that specific forest.

Therefore this assessment must be fully redone to examine solely the correct net sequestration and emissions, from the forest area that will be managed, accounting for all factors, and also accounting for the fact that near term net emissions over the next 20 years are the most significant because it is over the next 20 years that the planet is hitting a wide array of extremely dangerous climate crisis tipping points, and also because that is the proper window in which to analyze the forcing effect of methane (about 87 times higher than CO2 under that time frame).

3) Besides, and partly because of, the completely incorrect omission of soil carbon loss in the assessment, the net sequestration/emissions calculations in section 4.7 are far too optimistic and appear to be incorrect. This section does not properly and fully account for all emissions and sequestration losses, with an eye to new data which shows that after forests are disturbed it takes at least a century, and likely longer, for a disturbed forest to return to net sequestration of carbon. See links below which discuss these dynamics and which can serve as a starting point for redesigning and redoing your greenhouse gas analysis to make it an accurate one.

4) Chipping of felled and downed trees induces them to lose their carbon to the atmosphere much more rapidly. This assessment must be redone to show options for not chipping felled and downed trees at all, and instead leaving these trees intact, and on site, both as snags and downed trees. (See point 5.)

Chipping in Sutro Forest – 2016

5) Removing any vegetation (especially trees, including dead and felled trees) from a forest, drastically reduces the ecological capacity of that forest to uptake, store and retain carbon, and also dramatically reduces the crucial role of intact dead and dying trees to serve as wildlife habitat.

This DEIR contains no management assessment or mitigation plans that would call for a dramatic reduction in tree felling and removals in order to leave the forest and its soils as undisturbed as possible in order to maximize carbon sequestration, and maximize wildlife density and biodiversity through enhanced intact habitat. See the third link below to the report “The Myth of Catastrophic Wildfire” by expert forest ecologist Chad Hanson, PhD, to get a sense of, and some numbers on, the importance of leaving dead and dying trees intact and on site in a forest.

This assessment must be completely redone to show a management and mitigation option which *only* removes dead and dying trees *which pose a direct threat to human health and safety and property integrity* while leaving all other trees in the forest undisturbed. This assessment must include both net greenhouse gas, and wildlife density and diversity impacts.


Old-growth forests as global carbon sinks – Sebastiaan Luyssaert, et al
(contains extensive data showing that forests store more carbon the less they are disturbed)

Forest Carbon Basics – Mark E. Harmon, PhD (contains basic numbers for how forest and soil carbon dynamics operate over both short and long term timescales, and shows clearly that disturbed forests store less carbon for a century or longer)

The Myth of Catastrophic Wildfire – Chad Hansen, PhD
(See pages 19, 22 and 23 *and* referenced documents and studies)

Thanks for your attention to this extremely important matter.

Eric Brooks
Sustainability Chair, San Francisco Green Party
Campaign Coordinator, Our City SF

Sutro Forest

Sutro Forest viewed from Forest Knolls

Old Trees Trap More Carbon and Fight Climate Change

This article is reprinted with permission from, a website fighting to save the century-old forest on Mount Sutro in San Francisco, CA.

The older a tree grows, the more carbon dioxide it grabs out of the air and sequesters, thus fighting climate change. Cutting down these large old trees releases this carbon back into the atmosphere.


An article published in the Nature Journal summarizes the results of a huge research project by the US Geological Survey. This directly disproves the myth that young trees sequester carbon rapidly, but large old trees do not.

“The trees that are adding the most mass are the biggest ones, and that holds pretty much everywhere on Earth that we looked,” says Nathan Stephenson, an ecologist at the US Geological Survey in Three Rivers, California, and the first author of the study, which appears today [i.e. 15th January 2014]  in Nature.

“Trees have the equivalent of an adolescent growth spurt, but it just keeps going.”

The study, which looked at over 673 thousand trees of more than 400 species, found it was universally true.  This confirmed the results of a 2010 study that had focused on redwoods and on a eucalyptus species.

Former trees in a pile of woodchips sm

All the huge old trees that are cut down in San Francisco were fighting climate change – but now, whether as mulch or as rotting logs, they are contributing to it.


Here is the abstract of the study, from the NIH website [formatting and emphasis ours]:


Rate of tree carbon accumulation increases continuously with tree size.
Stephenson, Das, Condit, Russo, Baker, Beckman, Coomes, Lines, Morris, Rüger, Alvarez, Blundo, Bunyavejchewin, Chuyong, Davies, Duque, Ewango, Flores, Franklin, Grau, Hao, Harmon, Hubbell, Kenfack, Lin, Makana, Malizia, Malizia, Pabst, Pongpattananurak, Su, Sun, Tan, Thomas, van Mantgem, Wang, Wiser, Zavala.

Forests are major components of the global carbon cycle, providing substantial feedback to atmospheric greenhouse gas concentrations. Our ability to understand and predict changes in the forest carbon cycle–particularly net primary productivity and carbon storage–increasingly relies on models that represent biological processes across several scales of biological organization, from tree leaves to forest stands. Yet, despite advances in our understanding of productivity at the scales of leaves and stands, no consensus exists about the nature of productivity at the scale of the individual tree, in part because we lack a broad empirical assessment of whether rates of absolute tree mass growth (and thus carbon accumulation) decrease, remain constant, or increase as trees increase in size and age.

Here we present a global analysis of 403 tropical and temperate tree species, showing that for most species mass growth rate increases continuously with tree size. Thus, large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree.

The apparent paradoxes of individual tree growth increasing with tree size despite declining leaf-level and stand-level productivity can be explained, respectively, by increases in a tree’s total leaf area that outpace declines in productivity per unit of leaf area and, among other factors, age-related reductions in population density. Our results resolve conflicting assumptions about the nature of tree growth, inform efforts to undertand and model forest carbon dynamics, and have additional implications for theories of resource allocation and plant senescence.


And here is a link to the study itself in Nature: Rate of tree carbon accumulation increases continuously with tree size.






San Francisco Fells More Trees – Treasure Island

DSCN0052 - the beautiful trees of Treasure Island San Francisco - soon to be gone 2016

People have started writing to us about hundreds, perhaps thousands, of trees being clear-cut on Treasure Island – beautiful, healthy trees being destroyed. It’s happening right now.

One person wrote: “Over on the area where officers quarters are, there appears to be clear cutting is there any thing that can be done to save the ones left?

Then he sent us these pictures with the note: “Thanks for your attention to these matters. I am just a beer drinking football watching person, but perhaps I am more naive than I thought, because what I saw as represented by these images … was disturbing to a city person like myself.

DSCN0008 trees felled and dumped -Treasure Island san francisco 2016


DSCN0021 stumps and piles of mulch are all thats left - treasure island san francisco 2016

“These trees appear to have been just killed and then ground down to saw dust with no thought of conservation, reuse or anything, unconscionable,” he added.  I doubt the proud city of San Fran will ever mitigate the amount of trees they are killing today.”

huge old trees cut down on treasure island san francisco 2016Another person wrote:

“[On Treasure Island] I drove past several spots on the island where eucalyptus have been completely clear cut. I was driving so I couldn’t really get a good estimate, but it looks like many hundreds. Many of the trees were VERY large and healthy looking. They are already being chipped and/or logged…

“The work of the nativists? Looks like it to me. Otherwise why remove entire stands of healthy trees?

“I, for one, am sick and tired of this disgusting, unsupportable destruction that has no scientific or practical basis. These actions go beyond normal landscaping or aesthetic decisions. The city will suffer the effects of these actions for decades to come.

“Frankly, I’m also disappointed that the main opposition relies so heavily  on scientifically unsupportable counter-arguments. It makes it very hard to find effective ways to combat the destructive philosophy that has taken over Parks and Rec.”

DSCN0020 stumps and piles of mulch are all thats left - treasure island san francisco 2016

The huge eucalyptus trees of Treasure Island are among the sites where Monarch butterflies have been known to overwinter. Eucalyptus trees are great at sequestering carbon because of their dense wood, their fast growth, their huge size, and their long lives… if they’re not cut down like these trees here.

  • How many tons of sequestered carbon are now being released?
  • How much monarch butterfly over-wintering habitat has been destroyed?
  • How much tree cover for birds and animals has been removed?

How can San Francisco call itself a green city with this tree canopy shrinkage going on in these times of global warming?

monarch butterfly in a San Francisco eucalyptus tree - copyright Janet Kessler

Forests Store Carbon and Fight Climate Change

HillSideViewClimate change is upon us. Recently, we crossed the threshold of 400 parts per million of carbon dioxide in the Earth’s atmosphere – higher than at any time since humans populated our planet.

Aside from reducing carbon emissions, trees are the only way to fight climate change. They pull carbon dioxide from the air and store the carbon in their wood, roots, and the soil around them. But instead of planting trees, Native Plant interests are trying to fell trees to recreate a different ecosystem of shrubs and grasses. Multiple projects now threaten our Bay Area trees, with different rationales but the same underlying objective – native plants.

San Francisco’s Natural Areas program may fell 18,500 trees; the Sutro Forest project – 30,000 trees; the East Bay Hills projects – 500,000 trees. In addition, SFRPD is felling hundreds of trees in Golden Gate Park as ‘urban forestry’ and there’s the ‘normal’ destruction of trees for construction and similar purposes.

For this reason, we think the article below – reprinted with permission from Death of a Million Trees – is extremely important.


We believe that addressing climate change should be our highest environmental priority because it is the cause of many environmental problems. For example, a recent study found that changes in climate accounted for over half of the significant changes in vegetation all over the world in the past 30 years: “The climate governs the seasonal activity of vegetation…In humid mid-latitudes temperature is the largest influencing factor in plant growth. In predominantly dry areas, however, it is the availability of water and in the high altitudes incident solar radiation.” (1) Animals are affected by both changes in vegetation and climate, as exemplified by the shrinking home of the polar bear as Arctic ice melts.

The consensus amongst scientists is that increases in greenhouse gas emissions are the primary cause of climate change and carbon dioxide is the predominant greenhouse gas. Although the burning of fossil fuels is often considered the biggest source of greenhouse gas emissions, in fact transportation is responsible for only 10% of emissions. In contrast, deforestation is contributing 20% of greenhouse gas emissions because trees store carbon as they grow and release it into the atmosphere as carbon dioxide when the tree is destroyed. For that reason—and many others– we are opposed to the destruction of our urban forest.

Mount Sutro Forest is threatened with destruction because it is noy native.  Courtesy Save Sutro Forest.

Mount Sutro Forest is threatened with destruction because it is not native. Courtesy Save Sutro Forest.

Because our urban forest is predominantly non-native, native plant advocates are committed to defending the projects that are destroying the urban forest, which puts them in the awkward position of claiming that its destruction will not contribute to climate change. Here are a few of the arguments used by native plant advocates and the scientific evidence that those arguments are fallacious:

  • Since the native landscape in the Bay Area is grassland and scrub, native plant advocates often claim that these landscapes store more carbon than trees. In fact, trees store far more carbon than the native landscape because carbon storage is largely proportional to biomass. In other words, the bigger the plant, the more carbon it is capable of storing. (Carbon storage in plants and soils is explained in detail here.)
  • In the Draft Environmental Impact Report for San Francisco’s Natural Areas Program, native plant advocates claimed that destroying the forest and restoring grassland would lower ground temperatures based on a scientific study about the arctic north at latitudes above 50°. In fact, the point of that study was that snow reflects more light than trees. The Bay Area is far below 50° latitude and it doesn’t snow here, so that study is irrelevant to the Bay Area. (That study and its misuse by native plant advocates are reported here.)
  • Since most of the urban forest in the Bay Area was planted over 100 years ago, native plant advocates often claim that only young trees store carbon. Since carbon storage is largely proportional to biomass, mature trees store more carbon than small young trees. That is illustrated by this graph from the US Forest Service survey of San Francisco’s urban forest.
Larger trees store  more carbon at a faster rate

Larger trees store more carbon at a faster rate

  • The claim that young trees store more carbon is often made in connection with the equally bogus claim that “restoration” projects in the Bay Area will replace non-native trees with native trees. None of the plans for these projects propose to plant native trees where non-native trees are destroyed because that wasn’t the native landscape. In any case, native trees don’t tolerate the windy, dry conditions in which non-native trees are growing. For example, a study of historic vegetation in Oakland, California reported that only 2% of pre-settlement Oakland was forested with trees. (2)


Now that science has established the reality of climate change, most scientific inquiry has turned to how to stop it and/or mitigate it. For example, a recent study reports that planting forests where they did not exist in the past, quickly stores far more carbon in the soil than the treeless landscape. Scientists “…looked at lands previously used for surface mining and other industrial uses, former agricultural lands, and native grasslands where forests have encroached….[they] found that, in general, growing trees on formerly non-forested land increases soil carbon.” (3)

Here are their specific findings on each type of previously non-forested land:

  • “On a post-mining landscape, the amount of soil carbon generally doubled within 20 years and continued to double after that every decade or so.”
  • “The changes after cultivation of farm fields was abandoned and trees became established are much subtler, but still significant…at the end of a century’s time, the amount of soil carbon averages 15 percent higher than when the land was under cultivation…”
  • In places where trees and shrubs have encroached into native grassland, soil carbon increased 31 percent after several decades…”

Mainstream environmental organizations such as the Sierra Club claim to be concerned about climate change, yet they are the driving force behind the destruction of the urban forest in the San Francisco Bay Area. When will they wake up to the fact that advocating for the destruction of the urban forest is irresponsible for an environmental organization in the age of climate change?


(1) “A Look at the World Explains 90 Percent of Changes in Vegetation,” Science Daily, April 22, 2013.

(2) Nowak, David, “Historical vegetation change in Oakland and its implications for urban forest management,” Journal of Arboriculture, 19(5): September 1993

(3) “Soils in Newly Forested Areas Store Substantial Carbon That Could Help Offset Climate Change,” Science Daily, April 4, 2013.