Using the Berkeley Carbon Calculator to provide a conservative estimate of
the greenhouse gas benefits of a fuels or forest health treatment
Use case: Forest stand with little (if any) commercially sized trees that could be
sustainably harvested for sawlogs
Bill Stewart billstewart@berkeley.edu April 17, 2015
The Berkeley Carbon Calculator is well suited to estimate the greenhouse gas (GHG)
benefits for a range of treatments that can be applied to stands with mature trees.
As shown in Stewart and Sharma, (2015, in press) and Smyth, et al., 2014, most of
the GHG benefits from sustainably managed forests are related to the multiple
benefits from sawlogs that are primarily used to produce building materials. These
store carbon and “save” GHG that would have been used to produce alternative
building materials such as concrete and steel.
Of potentially greater need is a GHG benefit estimator for fuels reduction and
forest health treatments in forest stands with little potential to generate
revenue (and therefore no money to purchase expensive and complex modeling
efforts that may or may not produce valuable insights). These forests have the
potential to provide long term social benefits by reducing potential GHG losses from
wildfires, insect outbreaks, diseases, and other impacts to forest health that can also
affect adjacent forested acres.
The current drought; evidence of larger, hotter fires in forest stands; and increasing
severity of insect and disease related mortality all point towards a high level of risks
in California forests. Fuels treatments and forest health treatments that are tailored
to site conditions can reduce these risk factors. Accordingly, these types of
treatments are eligible for grant funding under Calfire’s Greenhouse Gas Reduction
Fund (GGRF) program.
As part of the application process for the GGRF program, submitters are required to
quantify the estimated GHG emission reductions of the project using a transparent
methodology. Since the costs of such estimates cannot be recovered, the value of
successful grants will be based on real project costs without any monetary valuation
of the future estimated GHG benefits. Projects on the California Air Resources Board
(ARB) website using the US Forest Offset Protocols are all for projects in areas with
very low wildfire and forest health risks of carbon loss. There is considerable
interest in simpler and more transparent GHG benefits calculators that are relevant
to the forests with high risks of carbon loss (i.e. forests other than the low risk, high
growth redwood region).
To address this need, we have added an additional scenario to the Berkeley Carbon
Calculator spreadsheet models for each of the four forest types that estimates the
GHG benefits of a fuels/forest health treatment that produces little if any high value
Draft guidance for using the Berkeley Carbon Calculator for thinning treatment 4/21/15
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products. This thinning treatment has been modeled into all the full cycle scenarios
in both the ‘let grow’ as well as the treatments, since it is commonly done when the
forest landowners have the ability to invest in activities with no immediate financial
returns. Projects that increase public health and safety, protect highly valued
wildlife habitats, and/or improve the overall quality of forest stands may not always
pencil out from a pure GHG benefits calculation that only considers carbon
sequestration or carbon releases. This is especially true if the project submitter has
to invest in an expensive modeling product before even applying for the grant.
The Berkeley Carbon Calculator uses a simple model to estimate the live tree carbon
benefits of an example fuels/forest health treatment in a young forest stand with
very limited potential to produce commercially valuable sawlogs. There are two
components to the estimated benefits:
1. A full life cycle carbon sequestration benefits estimate related to the sum of
the estimated gain in live tree carbon as well as the additional benefits from
the harvested products.
2. A probabilistic estimate of benefits related to the assumption that the treated
stand will be less susceptible to major carbon losses IF the stand is impacted
by a wildfire or an insect/disease outbreak event. While the ‘let grow’
baseline used to predict carbon sequestration in the model captures historic
rates of disturbance events in the FIA plots, there is considerable concern
that historical estimates will underestimate probable future losses.
The calculator also includes a worksheet that can be used to estimate carbon
benefits from thinning treatments in young stands designed to reduce fire or insect
risks. The ‘let grow’ option assumes the stand will be left to develop with a large
number of stems and considerable ladder fuels. The stand is projected to continue to
add live carbon, but there will be considerable loss to suppression mortality. The
‘best product utilization’ strategy is based on the empirical work documented in
Stewart and Nakamura (2012), where forest landowners conducted fuels and forest
health treatments AND were able to use around 75% of the harvested volume for
products. Less advantageous projects may only be able to sell ~50% of the collected
harvest for bioenergy or sometimes none of it. The least carbon beneficial action is
to pile burn all the harvested materials.
Draft guidance for using the Berkeley Carbon Calculator for thinning treatment 4/21/15
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Comparison of Sequestered Carbon with and without a fuels/forest
health thinning treatment at year 40 before considering how
treatment changes the probability of carbon losses
Sequestered Carbon (tonnes per hectare)
100
Energy from post-consumer
residues #1
90
Substitution Benefits #1
80
Landfill #1
70
60
Wood products #1
50
Energy from sawmill residues
#1
40
30
Energy from logging residues
#1
20
Regenerated forest #1
10
Logging slash left
0
0
20
40
Stand Age in Years
60
80
Let Grow Forest
The second component of the estimated carbon benefits of a fuels/forest health
treatment depends on changing the intensity and areal extent of potential future
wildfires and/or insect or disease outbreaks. While such events cover hundreds of
thousands of acres annually in California, the probability of an event hitting a
treated stand during the period when the treatment is effective is not 1.0. Without
good analysis of empirical data from remeasured stands, a second best approach is
to estimate the benefits for a plausible range of estimates of disturbance probability,
change in severity, and change in areal extent.
Fundamentally, treatments to reduce losses from probable future fire or insect
losses attempt to do two things. One is to reduce the intensity of the event in terms
of tree mortality percentage. For instance, changing the probable mix of wildfire
severity may not change the area burned, but will change how much live tree carbon
becomes dead tree carbon. A second is to reduce the area impacted by slowing
down the spread of the mortality agent and, for wildfires, providing more open
terrain for more effective fire suppression tactics. To date, there is limited
agreement on how to use empirical data to calibrate models. Very complex models
can and have been developed but they have the same weakness as very simple
models – we lack experience in calibrating them.
Draft guidance for using the Berkeley Carbon Calculator for thinning treatment 4/21/15
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Based the Berkeley Carbon Calculator’s simple spreadsheet model, our mid-range
estimate using a 1% annual disturbance probability, a drop in mortality from 54%
to 40%, and a drop in area impacted from 100% to 80% is that a successful
treatment would be estimated to ‘save’ around 5% of the average carbon inventory
of the project area when averaged across all sites whether or not they would be
impacted by an unexpected disturbance.
For our model system, a mixed conifer forest with a fuels/forest health treatment at
year 40, this means a gain of 3 metric tonnes of carbon. This benefit is of a similar
magnitude to the projected gains if the harvested products are used as efficiently as
products from thinning projects documented by Stewart and Nakamura (2012). The
following table summarizes the estimated benefits for different utilization of
harvested products AND the estimated benefit of the change in loss probability for
future disturbances not captured in the historical inventory data.
Table 1: Estimate C gain from tmts due to less tree-tree suppression losses and
increased resiliency for increasing risk of wildfire or other serious disturbances
Allocation of Cut Biomass (pct)
Carbon Benefit Calculation
C Disaster
Estimated
% gain in
loss
Avg C
average C
reduction
inventory
inventory
Bioenergy
Products
Decomposition
Pile
Burn
Avg C inv.
w/ no
disaster
No treatment
0%
0%
0%
0%
79
0
79
Best utilization
54%
21%
25%
0%
82
3
85
8%
38%
0%
62%
0%
80
3
83
5%
0%
0%
100%
0%
80
3
83
5%
0%
0%
0%
100%
78
3
81
3%
Action
½ collectable
slash to
bioenergy, ½
left
Thin and
scatter
Pile burn
Conclusion
There are known and increasing risks of significant carbon losses from wildfires,
insect outbreaks, and diseases in California forests. Recent estimates such as
Gonzalez, et al. 2015 estimate that around half of live tree carbon per hectare was
lost in areas affected by wildfires from 2001 to 2010. Recent surveys suggest
increasing losses from drought stress and insect outbreaks in California forests.
Using a simple set of assumptions (that can easily be altered in the spreadsheet), we
predict that well designed fuels and forest health treatments will have positive GHG
benefits even if many of the treated acres are not impacted by unexpected
disturbances.
Draft guidance for using the Berkeley Carbon Calculator for thinning treatment 4/21/15
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Works Cited
Gonzalez, Patrick, John J. Battles, Brandon M. Collins, Timothy Robards, and David S.
Saah. "Aboveground live carbon stock changes of California wildland ecosystems,
2001–2010." Forest Ecology and Management 348 (2015): 68-77.
Smyth, C. E., et al. "Quantifying the biophysical climate change mitigation potential
of Canada’s forest sector." Biogeosciences 11 (2014): 3515-3529.
Stewart, William C., and Benktesh D. Sharma. "Carbon calculator tracks the climate
benefits of managed private forests." California Agriculture 69, no. 1 (2015, in
press).
Stewart, William C., and Gary M. Nakamura. "Documenting the Full climate benefits
of Harvested Wood Products in Northern california: Linking Harvests to the Us
Greenhouse Gas Inventory." Forest Products Journal 62, no. 5 (2012).
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