APPENDIX A
ESTIMATED ECOSYSTEM SERVICES: METHODS AND ASSUMPTIONS
Estimated ecosystem services calculators are included in the application process to estimate the
carbon sequestration, stormwater intercepted and energy reductions in wastewater treatment
(Figure 01) from each proposal. These services are some of the key benefits that green
infrastructure provides to neighborhoods and municipal infrastructure. The social service benefits
provided by urban ecologies are difficult to quantify. Therefore health and well being benefits are
not included in the estimated ecosystem services calculators.
ECOSYSTEM SERVICES ESTIMATES I APPLICATION CALCULATORS
PROJECT TYPE
CARBON SEQUESTATION
STORMWATER
ENERGY AVOIDED
Urban Forest
X
X
Low Impact
Development
X
Not assessed due to lack of
available datasets and the
wide range of potential
project types. Methods will
continue to be evaluated.
X
X
Integrated Green
Infrastructure
X
X
X
Figure 01: The ecosystem services assessed for each project type. Methods for quantifying carbon
sequestration benefits from Low Impact Development projects will continue to be evaluated. In the grant
application calculator energy avoided is energy reductions in wastewater processes.
The estimated ecosystem services benefits calculators do not quantify changes in air quality or
energy saving in buildings. These services require nuanced site-specific analysis, which is not
possible in the current application process.
Finally, due to the range of potential project sizes
the benefit values generated by the estimated ecosystem calculators will not be a determining
factor in the funding evaluation process.
URBAN FOREST METHOD
An array of ecosystem services quantification methods and tools were evaluated to build the
Urban Forest estimated calculator (Figure 02). The Urban Forest project calculator has three main
goals: to be accessible, to achieve results with minimal inputs and to produce relevant baseline
on ecosystem services from a proposal. The most significant development challenge occurred at
the nexus of creating an accessible tool and producing locally appropriate datasets.
The first challenge was to determine a method for calculating ecosystem services from urban
trees. Since the tree species included in each proposal is unknown variable a representational
tree species system, based on species height and foliage patterns, was developed. The method
catalogues tree species into six categories: small evergreen (<20’ height at maturity), medium
evergreen (20'-35’ height at maturity), large evergreen (>35’ height at maturity), and small
deciduous, medium deciduous and large deciduous. The representational tree species system
simplifies the calculation method and provides reasonable, locally tailored estimates on the
amount of carbon sequestered and stormwater intercepted by a proposal.
SAN FRANCISCO CARBON FUND
1
APPENDIX A
URBAN FOREST ECOSYSTEM SERVICES QUANTIFICATION METHODS
QUANTIFICATION
RESOURCE
The Center
for Urban
Forest
Research
Tree Carbon
Calculator
(CTCC)
i-Tree Design
Northern
California
Coast
Community
Tree Guide
(Appendix 2)
EASY OF
USE
TIME
INTERVALS
& METHOD
SPECIES
DATABASE
ECOSYSTEM
SERVICES
Not intuitive
for nonexperts
Moderate
diversity
of species
Carbon
Sequestration,
Energy
avoided
(buildings)
Multi-year &
per year
analysis
The multi-year analysis
elevates the tools
effectiveness as an
advocacy tool for green
infrastructure.
Intuitive,
easy to use.
Relatively
wide
diversity
of species
Carbon
Sequestration,
Energy
avoided
(buildings), air
quality,
stormwater
Per year
analysis (1st
to the 99th
year)
(Not
Applicable)
Research
with datasets
that could be
used to build
quantificatio
n tools.
Limited
species
Key Interval
years. (5th,
10th, 15th,
20th, 25th,
30th, 35th,
40th)
Designed to
minimize
inputs from
user.
Focused
on trees
planted in
City of
San
Francisco
Carbon
Sequestration,
Energy
avoided
(buildings), air
pollution,
stormwater
intercepted,
and aesthetics
(resource unit
and economic
value)
Carbon
Sequestration,
stormwater
intercepted,
energy
reductions in
wastewater
treatment
Of the tools assessed,
i-Tree Design has the
largest variety of
species. However, the
absence of Latin names
is a drawback. It would
be helpful to pair
common names with
Latin names to improve
accuracy of the
calculators.
The representational
species (small, medium
and large) are not
representative of the
tree species planted in
the City of San
Francisco.
ASSESSMENT & KEY
FINDINGS
Integrates aspects of all
three of the researched
method: the strategy of
multi-year benefits from
CTCC, per year
datasets from i-Tree
Design and the
representational
species framework from
the NCCC Tree Guide.
Figure 02: Comparison chart of different methods for quantifying ecosystem services from urban trees.
CTCC is the approved Urban Forest quantification tool for the Climate Action Reserve’s Urban Forest
Protocols. Carbon information is broken down into 16 unique climate zones. I-Tree Design is a USDA Forest
Service tool for Urban Forest analysis, assessment and advocacy. Four ecological services are assessed
by i-Tree Design: carbon sequestration, stormwater intercepted, air quality and changes in energy use in a
building. The Northern California Coast Community Tree Guide is a study that analyzes the estimated
benefits and costs associated with tree plantings in the region. (McPherson, G. E., Simpson, J. R., Peper,
P. J., Crowell, A. M., & Xiao, Q. (2010). Northern California Coast Community Tree Guide: Benefits, Costs,
and Strategic Planting. Washington D.C. : United States Department of Agriculture.)
The Estimate
Ecosystem
Benefits
SAN FRANCISCO CARBON FUND
Cumulative
benefits for a
30-year time
period.
2
APPENDIX A
To support the development of relevant datasets for the City all of the representational trees
species are locally planted species. Urban Forest resources from Friends of the Urban Forest and
local Urban Forest experts were consulted in the species selection process. In addition the tree
species had to have accessible ecosystem services datasets. For each of the six categories three
locally planted species were selected (Figure 03).
LOCALLY PLANTED TREE SPECIES
SMALL
DECIDUOUS
MEDIUM
LARGE
Cherry Plum, Prunus
cerasifera 'Krauter
Vesuvius'
California Buckeye,
Aesculus californica
Western Redbud, Cercis
occidentalis
Trident Maple, Acer
buergeranum
Ginkgo, Ginkgo biloba
'Autumn Gold'
Goldenrain tree,
Koelreuteria paniculata
Crape Myrtle,
Lagerstroemia spp.
Evergreen Pear, Pyrus
kawakamii
Jacaranda, Jacaranda
mimosifolia
Common Linden, Tilia
cordata
California
Sycamore,Platanus x
acerifolia
'Bloodgood'/'Yarwood'
Magnolia, Magnolia
grandiflora
'Russet'/'Samuel'
Cork Oak,Quercas suber
EVERGREEN Kanooka, Tristaniopsis
laurina 'Elegant'
Coastal/Australian
Teatree, Leptospermum
laevigatum
Bronze Loquat, Eriobotrya
deflexa
Mayten, Maytenus boaria
Brisbane Box, Tristania
conferta
Figure 03: A chart of the locally planted trees that were selected to create the average values for
carbon sequestration and water intercepted for Urban Forest projects.
After the tree species were selected, the annual carbon sequestration and stormwater benefits
were summed for a thirty-year time frame. The estimated ecosystem services were extrapolated
from i-Tree Design. Then the thirty-year totals for the three tree species were averaged for each
category. The set of averages are the datasets integrated into the estimated ecosystem services
benefit calculators for Urban Forest project types (Figure 04).
DATASETS FOR URBAN FOREST ESTIMATED ECOSYSTEM SERVICES
SMALL
DECIDUOUS
EVERGREEN
MEDIUM
Carbon
Sequestration
(lbs)
1.223
Stormwater
(gallons)
Stormwater
(gallons)
9.706
Carbon
Sequestration
(lbs)
2,652
1,823
32,573
2,887
LARGE
Stormwater
(gallons)
14,181
Carbon
Sequestration
(lbs)
3,511
36,941
5,378
44,674
25,302
Figure 04: The annual datasets were extrapolated from i-Tree Design. The total 30-year benefits from the
three species per category were averaged. The values generated from the representational tree method
are integrated into the estimated Urban Forest ecosystem services calculator.
The thirty-year time period was selected for two reasons. First, the USDA Forest Service states
that the maximum potential for environmental benefits from urban trees occurs at thirty years.
Secondly, the growth rate for trees varies by species especially during the establishment and
juvenile stages of life. The variability in growth patterns results in a wide range of ecosystem
SAN FRANCISCO CARBON FUND
3
APPENDIX A
services from unique tree species. The thirty-year time period allows for the growth of trees to
stabilize and therefore generates a reasonable estimate of the ecological services provided during
the life span of an urban tree.
LOW IMPACT DEVELOPMENT
The City of San Francisco has a Combined Sewer System (CSS). This type of infrastructural
system has one set of structures for conveying raw sewage and urban runoff. The integration of
the two systems has risks. During intense rainstorms higher volumes of wastewater in the pipes
can overflow and release untreated sewage and stormwater into the San Francisco Bay.
Reducing stormwater runoff from streets and buildings will reduce overflow vulnerabilities. In
addition, managing stormwater where it falls allows urban ecosystems to be replenished with
rainwater and extra precipitation can infiltrate into the ground to recharge groundwater.
Low Impact Development, e.g. swales, wetlands, rain gardens, is a Green Infrastructure approach
to managing stormwater runoff. Low Impact Development improves hydrological function by
removing impervious surfaces and planting locally appropriate habitats. A network of Greening
projects creates a system of decentralized stormwater management sites that can be combined
with existing infrastructure to expand the capacity of a waste water system.
The Low Impact Development estimated ecosystem services calculators has three main goals:
to be accessible, to achieve results with minimal inputs and to estimate the change in direct
stormwater runoff from the site per year. The most significant development challenge for the
calculator came at the nexus of making the tool accessible and at the same time generating
relevant ecosystem services datasets. The Low Impact Development runoff calculator is adapted
from the Rational Method for calculating stormwater runoff (Marsh, 2005). The Rational Method
estimates the volume of stormwater runoff in a small watershed by calculating:
FORMULA (RATIONAL METHOD):
the area of the site X coefficient of runoff X intensity
of rainfall in inches/24 hour time period. The grant estimated ecosystem services
calculator has been adapted to:
FORMULA (SF CARBON FUND METHOD):
area of the site X coefficient of runoff X total
annual rainfall from >=0.25” precipitation days
The equation estimates the quantity of stormwater that overflows from the site per year.
The Low Impact Development calculator assumes that the site parameter is the boundary of the
watershed. Therefore the calculator only estimates the change in runoff based on the amount of
precipitation that is estimated to fall directly within the parameter of the site. Using the site
boundary as a proxy for the watershed simplifies the calculation method. This assumption is
necessary since it is assumed that the applicant will not be a stormwater management expert. To
increase the accuracy of the stormwater benefits the entire micro-watershed, which could include
area outside the project boundary, would need to be assessed. As the Grant Program matures
the Greening calculator will continue to be evaluated and adapted.
SAN FRANCISCO CARBON FUND
4
APPENDIX A
The grant calculator calculates the change in stormwater runoff as a direct result of a change in
the surface condition. The applicant will estimate the area of impervious and pervious surface for
the existing and proposed site. The runoff coefficients are extracted from the Rational Method.
The stormwater runoff coefficients embedded in the Greening calculator are 0.9 for impervious
surfaces and 0.2 for pervious surfaces (Marsh, 2005).
The total annual rainfall is derived from historical precipitation records for the City of San
Francisco. Monthly averages for total precipitation over 90 years were obtained from the Western
Regional Climate Center (WRCC) at the Mission Dolores monitoring site in San Francisco. During
that time period an average of 21.22” of precipitation fell at the Mission Dolores per year. In
addition, runoff is affected by the precipitation rates. The Greening quantification method assumes
that rainfall events with less than >=0.25” of rain in a 24 hour period do not produce significant
runoff. Therefore the percentage of monthly precipitation that fell on >=0.25” precipitation days
was estimated using datasets from NOAA National Climatic Data Center (Percent Frequencies of
>=.01”, >=.13”, >=.25”, >=.50”, and >=1” Precipitation-Days by Calendar Day- Downtown San
Francisco). The total monthly precipitation averages were multiplied by the average percentage
of rainfall that fell on >=0.25 / 24 precipitation days per month. According to the method an
average of 3.91” of precipitation falls on >=0.25 precipitation-days in downtown San Francisco
(Figure 05).
FORMULA: average
monthly rainfall X % of rainfall on >= 0.25 days per month = the
inches of rain per month from >= 0.25 precipitation days.
Estimated frequency of days with >=0.25 inches of
Monthly rainfall average
(WRCC) 1914-2006
rain / day (1921-2009)
Estimated % of precipitation per month
Month
November
December
January
February
March
April
May
June
July
August
September
October
15%
20%
24%
23%
18%
11%
4%
1%
0%
0%
3%
7%
2.61
4.08
4.4
3.8
2.88
1.41
0.57
0.15
0.02
0.05
0.23
1.02
inches of rainfall per
month that falls >=0.25 / 24
hours
0.3915
0.816
1.056
0.874
0.5184
0.1551
0.0228
0.0015
0
0
0.0069
0.0714
Total annual Rainfall (inches)
21.22”
3.91”
Figure 05: The data used to calculate the annual percentage of rain from a >=0.25” precipitation-days in
the City of San Francisco
ENERGY AVOIDED
Energy avoided is the reduction in energy to treat wastewater as a result of stormwater being
intercepted by trees or through increasing permeability of the site. In the City of San Francisco
SAN FRANCISCO CARBON FUND
5
APPENDIX A
the average dry weather flow is nine million gallons per day (MGD). According to The Carbon
Foot Print of Water an average facility that treats 10 MGD per day uses 1,791 kWh/MG to
processes advanced wastewater with nitrification. Therefore the grant calculator assumes it takes
approximately 0.0018 kWh to treat one gallon of wastewater. The change in stormwater runoff
(gallons) from the proposal is then multiplied by 0.0018 kWh to estimate the total energy avoided.
FORMULA:
volume of runoff avoided (gallons) X energy to treat wastewater (kWh)
GREENHOUSE GAS EMISSIONS AVOIDED
In the early stages of developing the ecosystem services calculator, the energy avoided was then
equated to reductions in greenhouse gas (GHG) emissions. However energy sources in the City
of San Francisco are categorized as carbon neutral.
EQUIVALENCIES
One of the main objectives of the estimated ecosystem benefits calculators is to increase
understanding about ecosystem services in the City of San Francisco. In order to increase the
meaning of the number generated by the calculators the values were equated to tangible
everyday experiences (Figure 06).
For example, the EPA’s Greenhouse Gas Equivalencies Calculator equates approximately
10,600 pounds of carbon dioxide with the annual greenhouse gas emissions from one passenger
vehicle. On the summary page of the benefits calculator the total amount of carbon sequestered
by the proposal is compared with annual emissions from (x) number of passenger vehicles.
Secondly, in the state of California the average resident consumes 55 gallons of water per day.
The volume of stormwater intercepted by the proposal is compared to average annual residential
water use for (x) number of residents. Finally the energy avoided is equated to the residential per
capita consumption of energy. In the City of San Francisco the residential per capita use is 1,716
kWh (2010 Community GHG Inventory, SF Environment Report).
SAN FRANCISCO CARBON FUND
6
APPENDIX A
Figure 06: A snap shot of estimated ecosystem services summary benefits. The summary page totals the
estimated benefits from the proposal and relates the values to tangible experiences.
RESOURCES
Griffiths-Sattenspiel, B., & Wilson, W. (2009). The Carbon Footprint of Water. The River
Network .
Marsh, W. M. (2005). Landscape Planning: Enviornmental Applications, vol.4. Hoboken: John
Wiley & Sons, Inc. .
McPherson, G. E., Simpson, J. R., Peper, P. J., Crowell, A. M., & Xiao, Q. (2010). Northern
California Coast Community Tree Guide: Benefits, Costs, and Strategic Planting. Washington
D.C. : United States Department of Agriculture.
Web Resources:
USDA Forest Service’s Ecosystem Services definition: http://www.fs.fed.us/ecosystemservices/
SAN FRANCISCO CARBON FUND
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APPENDIX A
i-Tree Design: http://www.itreetools.org/design.php
Western Regional Climate Center, WRCC: http://www.wrcc.dri.edu/cgi-bin/cliMONtpre.pl?casfod
NOAA National Climatic Data Center: http://www.climatestations.com/images/stories/sanfrancisco/sfpdays.gif
EPA’s Greenhouse Gas Equivalencies Calculator: http://www.epa.gov/cleanenergy/energyresources/calculator.html
2010 Community GHG Inventory a publication from SF Environment: (Forthcoming)
Friends of the Urban Forest: http://www.fuf.net/resources-reference/urban-tree-speciesdirectory/
.
SAN FRANCISCO CARBON FUND
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