Urban Forests and Climate Change
Preparers: Greg McPherson, Jim Simpson, Dan Marconett, Paula Peper, Elena Aguaron, Center for Urban Forest Research, Pacific Southwest Research Station
Figure 1. Trees sequester carbon dioxide as they grow, and reduce GHG emissions from power plants through energy conservation. Carbon dioxide is released through decomposition of removed wood and tree care activities that consume gasoline and diesel fuels. (drawing by Mike Thomas)
The Center for Urban Forest Research Tree Carbon Calculator (CTCC)
The CUFR Tree Carbon Calculator is the only tool approved by the California Climate Action Registry's Urban Forest Project Reporting Protocol for quantifying carbon dioxide sequestration from GHG tree planting projects. The CTCC is programmed in an Excel spreadsheet and provides carbon-related information for a single tree located in one of six California climate zones. Once the 
user enters information on the climate region and tree's size or age the CTCC produces information on:
- Carbon dioxide stored in the tree due to its growth over many years
- Carbon dioxide sequestered during the past year
- Dry weight of aboveground biomass that could be utilized if the tree was removed
If trees are strategically located to shade buildings and reduce energy consumed for heating and cooling, additional inputs are required. CTCC outputs include:
- Annual energy savings in kWh of electricity and MBtu of heating per tree
- Carbon dioxide equivalents of these energy savings
- The CTCC can be used to estimate GHG benefits for an existing tree or to forecast future benefits for a planting project.
Tree size and growth data are developed from samples of about 900 street trees representing approximately 20 predominant species in each of the six regional reference cities. Biomass equations, many derived from volumetric measurements of open-grown city trees, are used to derive total CO2 stored and sequestered. To determine effects of tree shade on building energy performance, over 12,000 simulations were conducted for each reference city using different combinations of tree sizes, locations, and building vintages.
Users should recognize that conditions vary within regions, and data from the CTCC may not accurately reflect their rate of tree growth, microclimate, or building characteristics. When conditions are different it may be necessary to apply biomass equations manually using adjusted tree growth data and perform building energy simulations with modified weather and tree data to more accurately depict effects of trees on GHGs.
The CTCC is intended as "proof of concept" software that is in the testing phase. It is provided "as is" without warranty of any kind. In 2009, data for other tree species in climate regions across the U.S. will be added, and in 2010, this version will be replaced by a Web-based version with greater functionality.
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Introduction
Urban forests have a role to play in reducing levels of carbon dioxide and other greenhouse gases (GHG) in the atmosphere. Urban trees reduce atmospheric carbon dioxide (CO2) through sequestration and reducing GHG emissions by conserving energy used for space heating and cooling (Figure 1). Carbon sequestration is the process by which CO2 is transformed into above- and belowground biomass and stored as carbon. During photosynthesis, atmospheric CO2 enters the leaf through stomata, combines with water, and is converted into cellulose, sugars, and other materials in a chemical reaction catalyzed by sunlight. Most of these materials become fixed as wood, although some are respired back as CO2 or used to make leaves that are eventually shed by the tree.
Tree shade reduces summer air conditioning demand, but can increase heating energy use by intercepting winter sunshine. Lowered air temperatures and wind speeds from increased tree cover can decrease both cooling and heating demand. Air conditioning and heating savings result in reduced GHG emissions from power plants. Reduced emissions can be substantial, especially in regions with large numbers of air-conditioned buildings, long cooling seasons, and where coal is the primary fuel for electric power generation.
Once trees die or are cut down, they begin to decompose and return stored carbon to the atmosphere. The rate of decomposition differs greatly based on the fate of the wood. Wood that is chipped and applied as mulch decomposes relatively quickly, while wood salvaged for use in wood products can survive 50 years or more, before gradually decomposing. The combustion of gasoline and diesel fuels by vehicle fleets, and by equipment such as chainsaws, chippers, stump removers, and leaf blowers is a GHG emission source. Typically, CO2 released due to tree planting, maintenance, and other program-related activities is about 2 to 5% of annual CO2 reductions obtained through sequestration and reduced power plant emissions.
Our initial research suggests that planting lots of trees in California communities can make a difference when it comes to fighting climate change. The California Global Warming Solutions Act of 2006 (AB32) requires a reduction in GHG emissions to 1990 levels by 2020. This amounts to a reduction of 173 Mt (million metric tons) from the predicted level in 2020. Using aerial photography, we found 242 million empty tree planting sites in California cities (McPherson and Simpson 2003). If 50 million trees were planted, they would sequester about 4.5 Mt CO2 (million tons) annually. If they were planted strategically to shade east and west walls of residential buildings, they would reduce air conditioning energy use by 6,408 GWh, equivalent to an average annual CO2 equivalent emission reduction of 1.8 Mt. The estimated total CO2 reduction of 6.3 Mt annually is 3.6% of the 173 Mt statewide goal, about the same as would be obtained from retrofitting homes with energy-efficient electric appliances.
Urban Forest Project Reporting Protocol [PDF 1.2 MB]
The Urban Forest Project Reporting Protocol provides detailed guidance to insure that tree projects meet eligibility requirements, produce GHG reductions that are additional to a baseline, are sustained for at least 100 years, and do not detract from management of existing trees. Also, it describes how to calculate and report carbon storage by project trees, as well as emissions associated with their maintenance.
The protocol was adopted by the California Air Resources Board and the California Climate Action Registry (CCAR). Urban forest projects anywhere in the U.S. can follow the new protocol and be reported to CCAR’s Climate Action Reserve, which will register and serialize GHG reductions after independent verification. If these offsets are sold or retired, the Climate Action Reserve will track their transaction, adding confidence and credibility to the voluntary carbon market.
Adoption of the Urban Forest Protocol sets the stage for investment in large-scale tree planting and stewardship projects because projects that adhere to the protocol’s guidance will generate real, reliable, additional, and permanent GHG reductions. Registered carbon reductions are "quality offsets" that pose less risk to investors than unregistered offsets. The market for quality offsets is growing as corporations, utilities, and individuals purchase them to offset their emissions or become carbon neutral.
Urban Forest Project Verification Protocol
[PDF 74 KB]
A separate verification protocol is used by independent verifiers to confirm that results are accurately reported. Independent verification reduces the risk and increases the value of carbon dioxide sequestered by urban forest projects.
Resources and Documents
Biomass utilization
A user guide for the community and urban forest inventory and management program [PDF 1.23 MB]
Abstract. The purpose of this study is to help communities manage their urban forests specifically in relation to the potential use of woody biomass rather than the more traditional and costly practice of disposal. This document presents the CUFIM, the Community and Urban Forest Inventory and Management program, a new Excel-based computer program that allows urban foresters control over their tree inventory. It also allows unprecedented options to determine volume of anticipated tree removals, and estimates of their dollar value. This program allows users to store and maintain up to 500 tree species and 50,000 tree records. In the future, potentially, communities can market their biomass for wood products and show an income from the woody resource rather than only a cost for maintenance and disposal.
Biomass in California: Challenges, Opportunities, and Potentials for Sustainable Management and Development [PDF 1.65 MB]
Abstract. Managing the nearly 100 million tons of biomass produced annually in California presents clear challenges and opportunities for technology, policy, and economic development. The sustainable management and use of biomass will provide environmental, social, and economic benefits far in excess of current practices. Concerted state and federal efforts are needed to change management and regulatory philosophies to better reflect the value of biomass as a renewable resource. This document explores issues in management and development of biomass and makes recommendations for future actions to realize the benefits.
Biopower Technical Assessment: State of the Industry and Technology [PDF 4.40 MB]
Abstract. Biopower (biomass-to-electricity generation), a proven electricity generating option in the United States and with about 11 GW of installed capacity, is the single largest source of non-hydro renewable electricity. This 11 GW of capacity encompasses about 7.5 GW of forest product industry and agricultural industry residues, about 3.0 GW of municipal solid waste-based generating capacity and 0.5 GW of other capacity such as landfill gas based production. The electricity production from biomass is being used and is expected to continue to be used as base load power in the existing electrical distribution system. An overview of biomass feedstock resources and sector and institutional barriers to biopower technology development is examined in this document. It encompasses the underlying policies, regulations, market development, and education needed to ensure the success of biopower. Environmental considerations are also discussed. Reviews of pertinent Federal government policies are provided. U.S. government policies are used to advance energy strategies such as energy security and environmental quality. Many of the benefits of renewable energy are not captured in the traditional marketplace economics. Government policies are a means of converting non-economic benefits to an economic basis, often referred to as "internalizing" of "externalities." This may be accomplished by supporting the research, development, and demonstration of new technologies that are not funded by industry because of projected high costs or long development time lines.
California urban woody green waste utilization [PDF 1.18 MB]
Abstract. This report deals with one of California's important "natural" resources, namely, urban trees that are removed for a wide variety of reasons and end-up clogging landfills, or at best are used for firewood or other low value commodities. Historically, productive utilization of this "waste material" for valuable lumber has been minimal; but in recent years, it's potential use has been recognized by a few resource managers and mill operators. The size of this potential resource, who is currently milling it, its physical characteristics, and how to get into the urban lumber producing business are the subjects of this report.
Physical properties and moisture relations of wood [PDF 500 KB]
Abstract. The versatility of wood is demonstrated by a wide variety of products. This variety is a result of a spectrum of desirable physical characteristics or properties among the many species of wood. In many cases, more than one property of wood is important to the end product. For example, to select a wood species for a product, the value of appearance-type properties, such as texture, grain pattern, or color, may be evaluated against the influence of characteristics such as machinability, dimensional stability, or decay resistance. Wood exchanges moisture with air; the amount and direction of the exchange (gain or loss) depend on the relative humidity and temperature of the air and the current amount of water in the wood. This moisture relationship has an important influence on wood properties and performance. This chapter discusses the physical properties of most interest in the design of wood products. Some physical properties discussed and tabulated are influenced by species as well as variables like moisture content; other properties tend to be independent of species. The thoroughness of sampling and the degree of variability influence the confidence with which species-dependent properties are known. In this chapter, an effort is made to indicate either the general or specific nature of the properties tabulated.
Quantifying urban saw timber abundance and quality in southeastern Lower Michigan, US [PDF 160 KB]
Abstract. There is a growing need for society to use resources efficiently, including effective use of dead and dying trees in urban areas. Harvesting saw timber from urban trees is a high-end use, but currently, much urban wood ends up in landfills or is used for wood chips or biomass fuel. To assess the general feasibility of harvesting urban wood, a regional estimate of urban saw timber quantity, quality, and availability was developed for a 13-county area in southeastern lower Michigan, U.S. Conservatively, over 16,000 m3 (560,000 ft3) of urban saw timber is estimated to become available each year in the study area from dead and dying trees, enough to supply the minimum annual needs of five small sawmills. The quality of wood in urban softwoods was generally low but comprised only a relatively small portion (10%) of urban wood. Wood quality of urban-grown hardwoods was comparable to that found in forests in the region, although the absolute volume was nine times less. Although there are potential concerns with harvesting urban trees for saw timber such as low availability and poor wood quality, the results of this study suggest that many of them may be unfounded.
Urban tree utilization and why it matters [PDF 646 KB]
Abstract. Most analyses related to U.S. timberland and timber production focus on forest land that is producing, or is capable of producing, more than 20 cubic feet per acre per year of industrial wood crops under natural conditions, is not withdrawn from timber use, and is not associated with urban or rural development. It's quite reasonable to focus our research and attention on these commercial forest lands due to their size and economic, social and environmental importance. However, there are other categories of forested areas in the U.S. that tend to "fall through the cracks," and that are rarely researched or discussed regarding their potential to provide wood-based products. Urban forests of the United States are such an example. It's estimated that today there are nearly 4 billion urban trees in the U.S., with another 70 billion trees growing in metropolitan areas. As urban land in the U.S. expands, so do the urban forests. Urban land in the lower 48 states increased from 2.5% of total land area in 1990 to 3.1% in 2000, an area about the size of Vermont and New Hampshire combined. Researchers from the U.S Forest Service project that urban land in the coterminous U.S. will nearly triple in size to over 8% by 2050. Utilization of urban trees for wood and paper products is still in its infancy. However, the idea is drawing more attention from researchers, community officials, arborists, tree care firms, and wood-using industries including bio-energy producers. Questions that often arise when discussing the potential for urban tree utilization include: How much wood is in our urban areas? What are the major constraints to utilizing this wood? Are there viable examples of urban tree utilization industries? Can bio-energy play a role in urban tree utilization? This report addresses these questions and concerns.
Energy conservation
Cool surfaces and shade trees to reduce energy use and improve air quality in urban areas [PDF 645 KB]
Abstract. Elevated summertime temperatures in urban 'heat islands' increase cooling-energy use and accelerate the formation of urban smog. Except in the city's core areas, summer heat islands are created mainly by the lack of vegetation and by the high solar radiation absorptance by urban surfaces. Analysis of temperature trends for the last 100 years in several large U.S. cities indicate that, since | 1940, temperatures in urban areas have increased by about 0.5-3.08°C. Typically, electricity demand in cities increases by 2-4% for each 18C increase in temperature. Hence, we estimate that 5-10% of the current urban electricity demand is spent to cool buildings just to compensate for the increased 0.5-3.08°C in urban temperatures. Downtown Los Angeles (L.A.), for example, is now 2.58°C warmer than in 1920, leading to an increase in electricity demand of 1500 MW. In L.A., smoggy episodes are absent below about 218°C, but smog becomes unacceptable by 328°C. Because of the heat-island effects, a rise in temperature can have significant impacts. Urban trees and high-albedo surfaces can offset or reverse the heat-island effect. Mitigation of urban heat islands can potentially reduce national energy use in air conditioning by 20% and save over $10B per year in energy use and improvement in urban air quality. The albedo of a city may be increased at minimal cost if high-albedo surfaces are chosen to replace darker materials during routine maintenance of roofs and roads. Incentive programs, product labeling, and standards could promote the use of high-albedo materials for buildings and roads. Similar incentive-based programs need to be developed for urban trees.
Energy effects of heat-island reduction strategies in Toronto, Canada. [PDF 155 KB]
Abstract. The effect of heat-island reduction (HIR) strategies on annual energy savings and peak-power avoidance of the building sector of the Greater Toronto Area is calculated, using an hourly building energy simulation model. Results show that ratepayers could realize potential annual energy savings of over $11M from the effects of HIR strategies. The residential sector accounts for over half (59%) of the total savings, offices 13% and retail stores 28%. Savings from cool roofs are about 20%, shade trees 30%, wind shielding of trees 37%, and ambient cooling by trees and reflective surfaces 12%. These results are preliminary and highly sensitive to the relative price of gas and electricity. Potential annual electrticity savings are estimated at about 150 GWh and potential peak power avoidance at 250 MW.
Evaluating the cost effectiveness of shade trees for demand-side management. [PDF 917 KB]
Abstract. Electric utilities are placing greater emphasis on demand-side management programs to defer construction of new generating facilities. Shade trees that are wisely selected and located can conserve cooling energy by directly shading buildings, as well as by lowering summertime temperatures via evapotranspirational (ET) cooling. Several utilities have found trees to be cost-effective energy conservation measures and have invested in shade tree programs for DSM. Also, urban trees are becoming part of electric utilities emission offset programs because of their ability to sequester carbon dioxide, intercept particulates, and absorb gaseous pollutants. However, the environmental, economic, and social benefits trees provide can be offset by costs associated with planting, pruning, removal and replacement of dead trees, disposal of green waste, water use, and biogenic hydrocarbon emissions. The cost effectiveness of trees for DSM is difficult to evaluate because few studies have documented avoided energy costs as tree mature, tree loss rates, current saturation and potential penetration of new energy conserving plantings. This article presents information on these topics to assist electrical utilities interested in evaluating shade trees as a DSM option.
Improved estimates of tree-shade effects on residential energy use [PDF 127 KB]
Abstract. Tree-shade alters building cooling and heating loads by reducing incident solar radiation. Estimates of the magnitude of this effect, and how it is influenced by urban forest structure (e.g. tree size and location), are difficult due to the complexity inherent in tree-sun-building interactions. The objective of this paper is to present a simplified method for making these estimates appropriate for neighborhood and larger scales. The method uses tabulated energy use changes for a range of tree types (e.g. size, shape) and locations around buildings (lookup tables), combined with frequency of occurrence of trees at those locations. The results are average change in energy use for each tree type that are not explicitly dependent on tree location. The method was tested by comparison to detailed simulations of 178 residences and their associated trees in Sacramento, California. Energy use changes calculated using lookup tables matched those from detailed simulations within +/-10%. The method lends itself to practical evaluation of these shading effects at neighborhood or larger scales, which is important for regional assessments of tree effects on energy use, and for development of tree selection and siting recommendations for proposed energy conserving planting programs.
Mitigating New York City's heat island with urban forestry, living roofs and light surfaces [PDF 4.15 MB]
Abstract. This study uses a regional climate model (MM5) in combination with observed meteorological, satellite, and GIS data to determine the impact of urban forestry, living (green) roofs, and light-colored surfaces on near-surface air temperature and the urban heat island in New York City. Nine mitigation scenarios are evaluated city-wide and in six case study areas. Temperature impacts are calculated both on a per-unit area basis, as well as taking into account the available land area for implementation, and other physical constraints. The scenarios are then evaluated based on their cost-effectiveness at reducing air temperature and resulting energy demand. All the mitigation strategies have a significant temperature impact. A combined strategy that maximizes the amount of vegetation in New York City by planting trees along streets and in open spaces, as well as by building living (or green) roofs (i.e. ecological infrastructure), offers more potential cooling than any individual strategy. Among the single-strategy scenarios, light surfaces, light roofs, and living roofs can potentially reduce the summer peak electric load more than the other strategies. The choice of a strategy should consider the characteristics and priorities of the neighborhood, including benefit/cost factors and the available area for implementation of each strategy.
Potential energy savings in buildings by an urban tree planting program in California [PDF 2.46 MB]
Abstract. Tree canopy cover data from aerial photographs and building energy simulations were applied to estimate energy savings from existing trees and new plantings in California. There are approximately 177.3 million energy-conserving trees in California communities and 241.6 million empty planting sites. Existing trees are projected to reduce annual air conditioning energy use by 2.5% with a wholesale value of $485.8 million. Peak load reduction by existing trees saves utilities 10% valued at approximately $778.5 million annually, or $4.39/tree. Planting 50 million trees to shade east and west walls of residential buildings is projected to reduce cooling by 1.1% and peak load demand by 4.5% over a 15-year period. The present wholescale value of annual cooling reductions for the 15-year period is $3.6 billion ($71/tree planted). Assuming total planting and stewardship costs of $2.5 billion ($50/tree), the cost of peak load reduction is $63/kW, considerably less than the $150/kW benchmark for cost-effectiveness. Influences of tree location near buildings and regional climate differences on potential energy savings are discussed.
Shade trees reduce building energy use and CO2 emissions from power plants. [PDF 147 KB]
Abstract. Urban shade trees offer significant benefits in reducing building air-conditioning demand and improving urban air quality by reducing smog. The savings associated with these benefits vary by climate region and can be up to $200 per tree. The cost of planting trees and maintaining them can vary from $10 to $500 per tree. Tree-planting programs can be designed to have lower costs so that they offer potential savings to communities that plant trees. Our calculations suggest that urban trees play a major role in sequestering CO2 and thereby delay global warming. We estimate that a tree planted in Los Angeles avoids the combustion of 18 kg of carbon annually, even though it sequesters only 4.5-11 kg (as it would if growing in a forest). In this sense, one shade tree in Los Angeles is equivalent to three to five forest trees. In a recent analysis for Baton Rouge, Sacramento, and Salt Lake City, we estimated that planting an average of four shade trees per house (each with a top view cross section of 50 m2) would lead to an annual reduction in carbon emissions from power plants of 16,000, 41,000, and 9000 t, respectively (the per-tree reduction in carbon emissions is about 10-11 kg per year). These reductions only account for the direct reduction in the net cooling- and heating-energy use of buildings. Once the impact of the community cooling is included, these savings are increased by at least 25%.
Urban and rural temperature trends in proximity to large US cities: 1951-2000 [PDF 3.19 MB]
Abstract. This paper presents a study of urban and rural temperature trends in proximity to the most populous metropolitan areas of the US. As data from urban meteorological stations are typically eliminated or adjusted for use in continental and global analyses of climate change, few studies have addressed how temperatures are changing in the areas most vulnerable to the public health impacts of warming: large cities. In this study, temperature data from urban and proximate rural stations for 50 large US metropolitan areas are analysed to establish the mean decadal rate of change in urban temperatures, rural temperatures, and heat island intensity over five decades. The results of this analysis find the mean decadal rate of change in the heat island intensity of large US cities between 1951 and 2000 to be 0.05° C and further show a clear division in temperature trends between cities situated in the northeastern and southern regions of the country.
Inventory and monitoring
A method for locating potential tree-planting sites in urban areas: A case study of Los Angeles, USA [PDF 1.36 MB]
Abstract. A GIS-based method for locating potential tree-planting sites based on land cover data is introduced. Criteria were developed to identify locations that are spatially available for potential tree planting based on land cover, sufficient distance from impervious surfaces, a minimum amount of pervious surface, and no crown overlap with other trees. In an ArcGIS environment, a computer program was developed to iteratively search, test, and locate potential treeplanting sites by virtually planting large, medium and small trees on plantable areas, with large trees given priority as more benefits are expected to accrue to them. A study in Los Angeles, USA found 2.2 million potential planting sites, approximately 109.3km2 of potential tree canopy cover.
A temporal analysis of urban forest carbon storage using remote sensing [PDF 242 KB]
Abstract. Quantifying the carbon storage, distribution, and change of urban trees is vital to understanding the role of vegetation in the urban environment. At present, this is mostly achieved through ground study. This paper presents a method based on the satellite image time series, which can save time and money and greatly speed the process of urban forest carbon storage mapping, and possibly of regional forest mapping. Satellite imagery collected in different decades was used to develop a regression equation to predict the urban forest carbon storage from the Normalized Difference Vegetation Index (NDVI) computed from a time sequence (1985-1999) of Landsat image data. This regression was developed from the 1999 field-based model estimates of carbon storage in Syracuse, NY. The total carbon storage estimates based on the NDVI data agree closely with the field-based model estimates. Changes in total carbon storage by trees in Syracuse were estimated using the image data from 1985, 1992, and 1999. Radiometric correction was accomplished by normalizing the imagery to the 1999 image data. After the radiometric image correction, the carbon storage by urban trees in Syracuse was estimated to be 146,800 tons, 149,430 tons, and 148,660 tons of carbon for 1985, 1992, and 1999, respectively. The results demonstrate the rapid and cost-effective capability of remote sensing-based quantitative change detection in monitoring the carbon storage change and the impact of urban forest management over wide areas.
Carbon storage by urban soils in the United States [PDF 1.82 MB]
Abstract. We used data available from the literature and measurements from Baltimore, Maryland to (i) assess inter-city variability of soil organic carbon (SOC) pools (1-m depth) of six cities (Atlanta, Baltimore, Boston, Chicago, Oakland, and Syracuse); (ii) calculate the net effect of urban land-use conversion on SOC pools for the same cities; (iii) use the National Land Cover Database to extrapolate total SOC pools for each of the lower 48 U.S. states; and (iv) compare these totals with aboveground totals of carbon storage by trees. Residential soils in Baltimore had SOC densities that were approximately 20 to 34% less than Moscow or Chicago. By contrast, park soils in Baltimore had more than double the SOC density of Hong Kong. Of the six cities, Atlanta and Chicago had the highest and lowest SOC densities per total area, respectively (7.83 and 5.49 kg mP2). On a pervious area basis, the SOC densities increased between 8.32 (Oakland) and 10.82 (Atlanta) kg m-2. In the northeastern United States, Boston and Syracuse had 1.6-fold less SOC post- than in pre-urban development stage. By contrast, cities located in warmer and/or drier climates had slightly higher SOC pools post- than in pre-urban development stage (4 and 6% for Oakland and Chicago, respectively). For the state analysis, aboveground estimates of C density varied from a low of 0.3 (WY) to a high of 5.1 (CA) kg m-', while belowground estimates varied from 4.6 (NV) to 12.7 (NH) kg m-2. The ratio of aboveground to belowground estimates of C storage varied widely with an overall ratio of 2.8. Our results suggest that urban soils have the potential to sequester large amounts of SOC, especially in residential areas where management inputs and the lack of annual soil disturbances create conditions for net increases in SOC. In addition, our analysis suggests the importance of regional variations of land-use and land-cover distributions, especially wetlands, in estimating urban SOC pools.
Methods for measuring and monitoring forestry carbon projects in California [PDF 928 KB]
Abstract. California's forest management activities offer an opportunity to sequester atmospheric carbon that constitutes a portion of the State's greenhouse gas (GHG) contribution. However, to evaluate the efficacy and cost-effectiveness of various forest management activities - as well as to support carbon trading ventures that may arise in the future - it is necessary to develop reliable, accepted carbon measuring and monitoring protocols. The project described in Methods for Measuring and Monitoring Forestry Carbon Projects in California sought to develop protocols for measuring and monitoring carbon emissions or removals from three forestry activities: afforestation, forest management, and forest preservation. The report presents California specific guidelines for measuring, monitoring, and estimating changes in carbon stocks in forest-based projects. Guidance is presented for developing a measuring plan for physically measuring all applicable carbon pools, and using the results from measurements to obtain estimates of carbon stocks. The focus of these guidelines is on field measurements designed to produce accurate net changes in carbon stocks to known levels of precision. Using the guidelines, California's decision makers will be able to evaluate forests management activities for the sequestration of carbon more easily, and California will benefit from better-targeted, more cost-efficient carbon sequestration.
Quantifying the role of urban forests in removing atmospheric carbon [PDF 588 KB]
Abstract. Urban land in the United States currently occupies about 69 million acres with an estimated average crown cover of 28% and an estimated tree biomass of about 27 tons/ acre. This structure suggests that the current total urban forest carbon storage in the United States is approximately 800 million tons with an estimated annual net carbon storage of around 6.5 million tons. Besides directly storing carbon, urban trees also reduce carbon dioxide (CO2) emissions by cooling ambient air and allowing residents to minimize annual heating and cooling. Approaches for understanding urban trees and CO2 flux are described at four scales: the nation, the city, the organization, and the individual. A method is provided that allows one to easily estimate the amount of carbon stored in an urban forest and sequestered annually by that forest. A method is provided for organizations to calculate the number of trees necessary to offset the CO2 emissions associated with the energy used in their office buildings. Tables are also provided to show how many trees an American could steward or plant to offset his or her per capita carbon emissions (2.3 tons/year).
Urban cover mapping using digital, high-spatial resolution aerial imagery [PDF 564 KB]
Abstract. High-spatial resolution digital color-infrared aerial imagery of Syracuse, NY was analyzed to test methods for developing land cover classifications for an urban area. Five cover types were mapped: tree/shrub, grass/herbaceous, bare soil, water and impervious surface. Challenges in high-spatial resolution imagery such as shadow effect and similarity in spectral response between classes were found. Classification confusion among objects with similar spectral responses occurred between water and dark impervious surfaces, concrete and baresoil, and grass/herbaceous and trees/shrub. Methods of incorporating texture, band ratios, masking of water objects, sieve functions, and majority filters were evaluated for their potential to improve the classification accuracy. After combining these various techniques, overall cover accuracy for the study area was 81.75%. Highest accuracies occurred for water (100%), tree/shrub (86.2%) and impervious surfaces (82.6%); lowest accuracy were for grass/herbaceous (69.3%) and bare soil (40.0%). Methods of improving cover map accuracy are discussed.
Planning, management, assessment
Adapting cities for climate change: the role of green infrastructure [PDF 275 KB]
Abstract. The urban environment has distinctive biophysical features in relation to surrounding rural areas. These include an altered energy exchange creating an urban heat island, and changes to hydrology such as increased surface runoff of rainwater. Such changes are, in part, a result of the altered surface cover of the urban area. For example less vegetated surfaces lead to a decrease in evaporative cooling, whilst an increase in surface sealing results in increased surface runoff. Climate change will amplify these distinctive features. This paper explores the important role that the green infrastructure, i.e. the green space network, of a city can play in adapting for climate change. It uses the conurbation of Greater Manchester as a case study site. The paper presents output from energy exchange and hydrological models showing surface temperature and surface runoff in relation to the green infrastructure under current and future climate scenarios. The implications for an adaptation strategy to climate change in the urban environment are discussed.
Air pollution removal by urban trees and shrubs in the United States [PDF 150 KB]
Abstract. A modeling study using hourly meteorological and pollution concentration data from across the coterminous United States demonstrates that urban trees remove large amounts of air pollution that consequently improve urban air quality. Pollution removal (O3, PM10, NO2, SO2, CO) varied among cities with total annual air pollution removal by US urban trees estimated at 711,000 metric tons ($3.8 billion value). Pollution removal is only one of various ways that urban trees affect air quality. Integrated studies of tree effects on air pollution reveal that management of urban tree canopy cover could be a viable strategy to improve air quality and help meet clean air standards.
Atmospheric carbon dioxide reduction by Sacramento's urban forest [PDF 512 KB]
Abstract. Sacramento County's 6 million trees store 8 million tons of CO (31 t/ha). and annually sequester 238.000 t (0 92 t/ha). Air-conditioning (157 GWh) and space-heating (145 TJ) savings from the urban forest further reduce emissions by 75 600 t of CO annually (0 29 t/ha). These avoided emissions are only 32"0 of the amount sequestered. due to a clean. hydroelectric energy supply. Annual CO2 release associated with tree maintenance is estimated at 9.400 t (0.04 t/ha), or 3'0 of the amount sequestered and avoided in net, the urban forest removes approximately 304.000 t (1.2 t/ha) each year, with an implied value of US $3.3 million ($0.55/tree). Carbon dioxide reduction by Sacramento's urban forest offsets the total amount of CO, emitted as a byproduct of human consumption by 1.8'%. Most benefits accrue on residential lands In the city and suburban sectors, where rates of storage and sequestration are about one-half those reported for U.S. forests. Guidelines for managing urban forests to reduce atmospheric CO are presented.
Atmospheric carbon reduction by urban trees [PDF 400 KB]
Abstract. Trees, because they sequester atmospheric carbon through their growth process and conserve energy in urban areas, have been suggested as one means to combat increasing levels of atmospheric carbon. Analysis of the urban forest in Oakland, California (21% tree cover), reveals a tree carbon storage level of 11.0 metric tons/hectare. Trees in the area of the 1991 fire in Oakland stored approximately 14500 metric tons of carbon, 10% of the total amount stored by Oakland's urban forest. National urban forest carbon storage in the United States (28% tree cover) is estimated at between 350 and 750 million metric tons. Establishment of 10 million urban trees annually over the next 10 years is estimated to sequester and offset the production of 363 million metric tons of carbon over the next 50 years-less than 1% of the estimated carbon emissions in the United States over the same time period. Advantages and limitations of managing urban trees to reduce atmospheric carbon are discussed.
Carbon accounting rules and guidelines for the United States forest sector [PDF 1.34 MB]
Abstract. The United States Climate Change initiative includes improvement of Energy's Voluntary Greenhouse Gas Reporting Program. The program includes specific accounting rules and guidelines for reporting and registering forestry activities that reduce atmospheric C02 by increasing carbon sequestration or reducing emissions. In the forestry sector, there is potential for the economic value of emissions credits to provide increased income for landowners, to support rural development, to facilitate the practice of sustainable forest management, and to support restoration of ecosystems. Forestry activities with potential for achieving substantial reductions include, but are not limited to: afforestation, mine land reclamation, forest restoration, agroforestry, forest management, short-rotation biomass energy plantations, forest protection, wood production, and urban forestry. To be eligible for registration, the reported reductions must use methods and meet standards contained in the guidelines. Forestry presents some unique challenges and opportunities because of the diversity of activities, the variety of practices that can affect greenhouse gases, year-to-year variability in emissions and sequestration, the effects of activities on different forest carbon pools, and accounting for the effects of natural disturbance.
Carbon dioxide reduction through urban forestry: guidelines for professional and volunteer tree planters [PDF 2.54 MB]
Abstract. This document has been developed by the Pacific Southwest Research Station's Center for Urban Forest Research as a tool for utilities, urban foresters and arborists, municipalities, consultants, non-profit organizations and others to determine the effects of urban forests on atmospheric carbon dioxide (CO2) reduction. The calculation of CO2 reduction that can be made with the use of these Guidelines enables decision makers to incorporate urban forestry into their efforts to protect our global climate. With these Guidelines, they can: report current and future CO2 reductions through a standardized accounting process; evaluate the cost-effectiveness of urban forestry programs with CO2 reduction measures; compare benefits and costs of alternative urban forestry program designs; and produce educational materials that assess potential CO2 reduction benefits and provide information on tree selection, placement, planting, and stewardship.
Carbon accounting rules and guidelines for the United States forest sector [PDF 1.34 MB]
Abstract. There is increasing concern about the predicted negative effects of the future doubling of carbon dioxide on the earth. This concern has evoked interest in the potential for urban greenspace to help reduce the levels of atmospheric carbon. This study quantifies greenspace-related carbon storage and annual carbon fluxes for urban residential landscapes. For detailed quantification, the scale of this study was limited to two residential blocks in northwest Chicago which had a significant difference in vegetation cover. Differences between the two blocks in the size of greenspace area and vegetation cover resulted in considerable differences in total carbon storage and annual carbon uptake. Total carbon storage in greenspace was about 26.15 kg/m2 of greenspace in study block 1, and 23.20 kg/m2 of greenspace in block 2. Of the total, soil carbon accounted for approximately 78.7% in block 1 and 88.7% in block 2. Trees and shrubs in block 1 and block 2 accounted for 20.8% and 10.6%, respectively. The carbon storage in grass and other herbaceous plants was approximately 0.5-0.7% in both blocks. Total net annual carbon input to the study blocks by all the greenspace components was in the region of 0.49 kg/m2 of greenspace in block 1 and 0.32 kg/m2 of greenspace in block 2. The principal net carbon release from greenspaces of the two residential landscapes was from grass maintenance. Greenspace planning and management strategies were explored to minimize carbon release and maximize carbon uptake.
Guidelines for Developing and Evaluating Tree Ordinances [PDF 1.65 MB]
Abstract. This document provides a variety of tools and resources for citizens and local governments interested in developing, revising, or evaluating local tree ordinances. Rather than using a "model ordinance" approach, we describe how tree ordinance development can be integrated with an overall community tree management program. It includes annotated examples of effective tree ordinance provisions used throughout the country. We also provide detailed descriptions of practical methods used to monitor community tree resources, tree management activities, and community attitudes. The purpose is to provide practical information for communities dealing with tree ordinances and other urban forest management issues. We also hope to provide a means for sharing successful ordinance provisions and urban forest evaluation and monitoring methods used in cities and counties throughout the country.
Impacts of urban greenspace on offsetting carbon emissions for middle Korea [PDF 196 KB]
Abstract. Carbon dioxide is an important greenhouse gas and a major agent of climate change. This study quantified carbon (C) emissions from energy consumption and C storage and uptake by greenspace for three cities in middle Korea: Chuncheon, Kangleung, and Seoul. Carbon emissions were estimated using C emission coefficients for fossil fuels consumed. Carbon storage and uptake by woody plants were computed applying biomass equations and radial growth rates. The soils in Chuncheon were cored to analyze organic C storage. Annual C emissions were 37_0 t/ha/yr in Kangleung, 47_2 t/ha/yr in Chuncheon, and 264_9 t/ha/yr in Seoul. Mean C storage by woody plants ranged from 26_0 to 60_1 t/ha for natural lands within the study cities, and from 4_7 to 7_2 t/ha for urban lands (all land use types except natural and agricultural lands). Mean annual C uptake by woody plants ranged from 1_60 to 3_91 t/ha/yr for natural lands within the cities, and from 0_53 to 0_80 t/ha/yr for urban lands. There were no significant differences (95% confidence level) between the cities in C storage and uptake per ha for urban lands. Organic C storage in Chuncheon soils (to a depth of 60 cm) averaged 31_6 t/ha for natural lands and 24_8 t/ha for urban lands. Woody plants stored an amount of C equivalent to 6_0-59_1% of total C emissions within the cities, and annually offset total C emissions by 0_5-2_2%. Carbon storage in soils was 1_2 times greater than that by woody plants in Chuncheon. The C reduction benefits of woody plants were greater in Chuncheon and Kangleung, where areal distribution of natural lands was larger and the population density lower than in Seoul. Strategies to increase C storage and uptake by urban greenspace were explored.
Municipal forest benefits and costs in five U.S. cities [PDF 268 KB]
Abstract. Increasingly, city trees are viewed as a best management practice to control stormwater, an urban-heat-island mitigation measure for cleaner air, a CO2-reduction option to offset emissions, and an alternative to costly new electric power plants. Measuring benefits that accrue from the community forest is the first step to altering forest structure in ways that will enhance future benefits. This article describes the structure, function, and value of street and park tree populations in Fort Collins, Colorado; Cheyenne, Wyoming; Bismarck, North Dakota; Berkeley, California; and Glendale, Arizona. Although these cities spent $13- 65 annually per tree, benefits ranged from $31 to $89 per tree. For every dollar invested in management, benefits returned annually ranged from $1.37 to $3.09. Strategies each city can take to increase net benefits are presented.
Pollution mitigation and carbon sequestration by an urban forest. [PDF 195 KB]
Abstract. At the beginning of the 1900s, the Canberra plain was largely treeless. Graziers had carried out extensive clearing of the original trees since the 1820s leaving only scattered remnants and some plantings near homesteads. With the selection of Canberra as the site for the new capital of Australia, extensive tree plantings began in 1911. These trees have delivered a number of benefits, including aesthetic values and the amelioration of climatic extremes. Recently, however, it was considered that the benefits might extend to pollution mitigation and the sequestration of carbon. This paper outlines a case study of the value of the Canberra urban forest with particular reference to pollution mitigation. This study uses a tree inventory, modelling and decision support system developed to collect and use data about trees for tree asset management. The decision support system (DISMUT) was developed to assist in the management of about 400,000 trees planted in Canberra. The size of trees during the 5-year Kyoto Commitment Period was estimated using DISMUT and multiplied by estimates of value per square meter of canopy derived from available literature. The planted trees are estimated to have a combined energy reduction, pollution mitigation and carbon sequestration value of US$20-67 million during the period 2008-2012.
The interactions between urban forests and global climate change. [PDF 7.14 MB]
Abstract. Urban forests are comprised of all trees within urban areas. These trees, whether found individually or in stands, can affect global climate change by affecting the urban atmosphere and various chemical emissions. Urban vegetation, because of its close proximity to numerous emission sources, can have increased impacts on global climate change through both direct (e.g., removal of green house gases) and indirect (e.g., altering nearby emissions) effects. Conversely, changes in urban climate associated with climate change can affect the urban forest. The purpose of this paper is to explore the numerous ways that urban forests and global climate change interact and thereby affect urban and global environmental quality.
The potential of urban tree plantings to be cost effective in carbon credit markets [PDF 262 KB]
Abstract. Emission trading is considered to be an economically sensitive method for reducing the concentrations of greenhouse gases, particularly carbon dioxide, in the atmosphere. There has been debate about the viability of using urban tree plantings in these markets. The main concern is whether or not urban planting projects can be cost effective options for investors. We compared the cost efficiency of four case studies located in Colorado, and used a model sensitivity analysis to determine what variables most influence cost effectiveness. We believe that some urban tree planting projects in specific locations may be cost effective investments. Our modeling results suggest that carbon assimilation rate, which is mainly a function of growing season length, has the largest influence on cost effectiveness, however resource managers can create more effective projects by minimizing costs, planting large-stature trees, and manipulating a host of other variables that affect energy usage.
The urban forest in Beijing and its role in air pollution reduction [PDF 522 KB]
Abstract. Tree planting has been proposed by the municipal government as a measure to alleviate air pollution in Beijing, the capital of China. This study examines that proposal. It is based on the analyses of satellite images and field surveys to establish the characteristics of current urban forest in the central part of Beijing. The influence of the urban forest on air quality was studied using the Urban Forest Effects Model. The results show that there are 2.4 million trees in the central part of Beijing. The diameter distribution of the trees is skewed toward small diameters. The urban forest is dominated by a few species. The condition of trees in the central part of Beijing is not ideal; about 29% of trees were classified as being in poor condition. The trees in the central part of Beijing removed 1261.4 tons of pollutants from the air in 2002. The air pollutant that was most reduced was PM10 (particulate matters with an aerodynamic diameter smaller than 10 mm), the reduction amounted to 772 tons. The carbon dioxide (CO2) stored in biomass form by the urban forest amounted to about 0.2 million tons. Future research directions to improve our understanding of the role of individual tree species in air pollution reduction are discussed.
Urban ecosystems and the North American carbon cycle [PDF 181.37 KB]
Abstract. Approximately 75-80% of the population of North America currently lives in urban areas as defined by national census bureaus, and urbanization is continuing to increase. Future trajectories of fossil fuel emissions are associated with a high degree of uncertainty; however, if the activities of urban residents and the rate of urban land conversion can be captured in urban systems models, plausible emissions scenarios from major cities may be generated. Integrated land use and transportation models that simulate energy use and traffic-related emissions are already in place in many North American cities. To these can be added a growing dataset of carbon gains and losses in vegetation and soils following urbanization, and a number of methods of validating urban carbon balance modeling, including top down atmospheric monitoring and urban 'metabolic' studies of whole ecosystem mass and energy flow. Here, we review the state of our understanding of urban areas as whole ecosystems with regard to carbon balance, including both drivers of fossil fuel emissions and carbon cycling in urban plants and soils. Interdisciplinary, whole-ecosystem studies of the socioeconomic and biophysical factors that influence urban carbon cycles in a range of cities may greatly contribute to improving scenarios of future carbon balance at both continental and global scales.
Popular articles
Guideline specifications for nursery tree quality. Selecting quality nursery stock [PDF 1.65 MB]
Abstract. A committee comprised of municipal arborists, urban foresters, nurserymen, U.C. Cooperative Extension horticultural advisors, landscape architects, non-profit tree groups and horticultural consultants developed the attached specifications to ensure high quality landscape trees. After more than a year of work, they succeeded in drafting a document entitled Specification Guidelines for Container-grown Trees for California. This document will be published and the guidelines promoted throughout the nursery and landscape industry. Its intent is to help landscape professionals develop their own comprehensive and detailed specifications to ensure that they obtain high quality container-grown nursery trees. The document is also intended to help nursery professionals in their efforts to improve the quality of trees grown in California. These specifications can be modified for specific simulations.
Leafy, green and good.[PDF 20 KB]
Abstract. This document presents Greg McPherson's Op-Ed in the Los Angeles Times on the role of urban trees in combating global warming. "Fighting climate change is complicated - but the benefits of trees in cities are not an illusion..."
New protocol enables local governments, others to receive emissions offsets for planting tree programs [PDF 28 KB]
Abstract. This document is a press release informing that the Board of Directors for the California Climate Action Registry, a private nonprofit organization committed to solving climate change through emissions reporting and reduction, approved the Urban Forest Project Reporting Protocol. This is the first California Registry protocol to benefit local governments and others through offset credits for planting trees in urban settings.
Researchers develop computer program to aid in urban tree management [PDF 86 KB]
Abstract. This project culminated in the development of the Community and Urban Forest Inventory and Management program (CUFIM), a new Excel-based computer program that enhances urban foresters' control over their tree inventory. It also allows unprecedented options to determine volume of anticipated tree removals and estimates of their dollar value. The program allows users to store and maintain up to 500 tree species and 50,000 tree records. The program is designed for beginners, but as skill levels increase, a number of advanced options are also available. A number of different kinds of tables can be printed that provide a hard copy of the database and summarize the number of trees and volume by diameter class. Biomass value can also be assessed through three different approaches. The documentation and notes provide assistance to the user including suggestions for setting up the database, the recommended precision of measurement units, and diameter and height class interval requirements. A number of examples are included to illustrate main points.
Urban forests and climate change: Project Reporting Protocol summary [PDF 608 KB]
Abstract. Urban forests have a role to play in reducing levels of carbon dioxide and other greenhouse gases (GHG) in the atmosphere. However, very few GHG tree projects have been undertaken because of uncertainty regarding their performance and permanence. The Urban Forest Project Reporting Protocol was developed to reduce this uncertainty by providing a standard set of guidelines for use throughout the United States. This document summarizes the characteristics and importance of this Protocol.
Urban tree planting and urban gas reductions [PDF 68 K
Abstract. This document presents the CUFR's take on the value of trees in fighting climate change.
Protocols
Urban Forest Project Reporting Protocol
[PDF 1.20 MB]
Abstract. The California Climate Action Registry's (California Registry) Urban Forest Project Reporting Protocol provides guidance to account for and report greenhouse gas (GHG) emission reductions associated with a planned set of tree planting and maintenance activities to permanently increase carbon storage in trees. The California Registry is a leading source of accurate, transparent, and credible GHG accounting standards for reporting entity-wide GHG emission inventories. The California Registry also applies its knowledge and expertise in GHG accounting to the quantification of GHG emission reductions associated with specific project activities, to ensure the environmental integrity of programs based on these data and to support international efforts to combat climate change. Through its Climate Action Reserve program (the Reserve), the California Registry supplies protocols such as this one for quantifying GHG emission reductions (or offsets). In addition, it oversees and accredits independent third-party verifiers, and provides a web-based publicly accessible offset registration, serialization, and tracking service. Project developers that implement tree-planting programs use this document to register GHG reductions with the Reserve. It provides eligibility rules, methods to calculate reductions, performance monitoring instructions, and procedures for reporting project information to the Reserve. Additionally, all project reports receive annual, independent verification by California Registry-approved verifiers. Guidance for verifiers to certify reductions is provided in the corresponding Urban Forest Project Verification Protocol.
Urban forest project verification protocol [PDF 76 KB]
Abstract. The California Climate Action Registry's (California Registry) Urban Forest Project Verification Protocol provides guidance to California Air Resources Board (CARB) and California Registry approved verifiers for verifying greenhouse gas (GHG) emission reductions associated with a planned set of tree planting and maintenance activities to permanently increase carbon storage, in accordance with the California Registry's Urban Forest Project Reporting Protocol. Verification occurs on an annual basis. This verification protocol supplements the California Registry's General Verification Protocol (GVP). It describes the core verification activities in the context of an urban forest project and provides information on project monitoring parameters. The purpose of verification is to provide an independent review of data and information used to produce a GHG project report. It aims to ensure that a participant's emissions report meets the following quality criteria: completeness, consistency, accuracy, comparability and transparency. The intended audience of the project verification protocol is approved verifiers. However, urban forest project developers will also find it useful to review this document to develop a better understanding of the verification activities associated with reporting GHG reductions to the California Registry. Only CARB and California Registry approved forest sector verifiers are eligible to verify Urban Forest Project reports. Approved verifiers under the California Registry's GVP are not automatically permitted to verify the project reports. To become an approved forest sector verifier, a general verifier must successfully complete a forest sector-specific application process.
Sequestration and pollutant uptake
A review of the accuracy of urban forestry biomass functions: utility for the California climate action registry protocol [PDF 56 KB]
Abstract. A question regarding the accuracy of the biomass functions for urban forestry settings was raised during the development phase of the urban forestry protocol for the California Climate Action Registry (CCAR). Specifically, the relative accuracy of the urban forestry biomass functions for each in situ carbon pool compared to wildland forestry biomass functions was questioned. To address this query an error analysis was performed that characterized the statistical variability and appropriateness of application of the biomass functions to urban areas of the State. The general findings were that there was no evidence that the methods presented in the protocols for estimating biomass were any less reliable on average than their wildland counterparts. Professional analysis in the application and improvement of biomass estimates is encouraged, which is consistent with the wildland application of allometric functions to tree inventory data.
Comprehensive Database of Diameter-based Biomass Regressions for North American Tree Species [PDF 660 KB]
Abstract. A database consisting of 2,640 equations compiled from the literature for predicting the biomass of trees and tree components from diameter measurements of species found in North America. Bibliographic information, geographic locations, diameter limits, diameter and biomass units, equation forms, statistical errors, and coefficients are provided for each equation, along with examples of how to use the database. The CD-ROM included with this publication contains the complete database (Table 3) in spreadsheet format (Microsoft Excel 2002© with Windows XP©).
Allometric scaling theory applied to FIA biomass estimation . [PDF 824 KB]
Abstract. Tree biomass estimates in the Forest Inventory and Analysis (FIA) database are derived from numerous methodologies whose abundance and complexity raise questions about consistent results throughout the U.S. A new model based on allometric scaling theory ("WBE") offers simplified methodology and a theoretically sound basis for improving the reliability and usefulness of biomass estimation for all tree species. Although a complete test of the WBE theory is beyond the scope of this paper, implications of the theory are explored from results of another study consistent with WBE theory. Two interesting results were found: (1) a simplified approach using 10 generalized equations is within 10 to 40 percent of FIA county-scale biomass estimates, and (2) of the two methods, FIA's methodology appears more inconsistent from State to State.
Tree species selection, design and management to improve air quality. [PDF 2.99 MB]
Abstract. Urban areas currently occupy 3.5% of the conterminous United States and contain approximately 80% of the U.S. population. Many urban areas often have relatively poor air quality that impacts human health. Because of their close proximity to people and numerous emission sources, urban trees affect local and regional air quality. With proper species selection, design, and management, urban trees can help improve air quality.
Carbon storage and sequestration by urban trees in the USA [PDF 132 KB]
Abstract. Based on field data from 10 USA cities and national urban tree cover data, it is estimated that urban trees in the coterminous USA currently store 700 million tonnes of carbon ($14,300 million value) with a gross carbon sequestration rate of 22.8 million tC/yr ($460 million/year). Carbon storage within cities ranges from 1.2 million tC in New York, NY, to 19,300 tC in Jersey City, NJ. Regions with the greatest proportion of urban land are the Northeast (8.5%) and the southeast (7.1%). Urban forests in the north central, northeast, south central and southeast regions of the USA store and sequester the most carbon, with average carbon storage per hectare greatest in southeast, north central, northeast and Pacific northwest regions, respectively. The national average urban forest carbon storage density is 25.1 tC/ha, compared with 53.5 tC/ha in forest stands. These data can be used to help assess the actual and potential role of urban forests in reducing atmospheric carbon dioxide, a dominant greenhouse gas.
Effects of tree cover on parking lot microclimate and vehicle emissions [PDF 152 KB]
Abstract. A pilot study was performed to measure the difference in parking lot microclimate resulting from the presence or absence of shade tree cover. Microclimate data from contrasting shade regimes were then used as input to a motor vehicle emissions model. Model results were used to estimate the potential for regional increases in parking lot tree cover to reduce motor vehicle hydrocarbon and nitrogen oxide (NOx) emissions.
Sacramento's parking lot shading ordinance: environmental and economic costs of compliance [PDF 644 KB]
Abstract. A survey of 15 Sacramento parking lots and computer modeling were used to evaluate parking capacity and compliance with the 1983 ordinance requiring 50% shade of paved areas (PA) 15 years after development. There were 6% more parking spaces than required by ordinance, and 36% were vacant during peak use periods. Current shade was 14% with 44% of this amount provided by covered parking. Shade was rojected to increase to 27% (95% CI 24-37%) when all lots in the sample were 15-year-old. Annual benefits associated with the corresponding level of tree shade were estimated to be US$ 1.8 million (CI US$ 1.5-2.6 million) annually citywide, or US$ 2.2 million less than benefits from 50% shade (CI US$ 1.4-2.5 million). The cost of replacing dying trees and addressing other health issues was US$ 1.1 million. Planting 116,000 trees needed to achieve 50% shade was estimated to cost approximately US$ 20 million. Strategies for revising parking ordinances to enhance their effectiveness are presented.
Physical properties and moisture relations of wood [PDF 500 KB]
Tree volume equations for fifteen urban species in California [PDF 2.97 MB]
Abstract. This project conducts a series of volume studies of the 15 major urban forest species to further the development of management inventories in each California city for the purpose of promoting urban forests. This document develops the tree volume equations and explains the development of community forest inventories.
Specific gravity, moisture content and density relationship for wood [PDF 852 KB]
Abstract. This report reviews the basis for determining values for the density of wood as it depends on moisture content and specific gravity. The data are presented in several ways to meet the needs of a variety of users.
Book
Abdollahi, K.K.; Ning, Z.H.; Appeaning, A. 2000. Global climate change and the urban forest . Baton Rouge, LA; Franklin Press, Inc, 77 p.
Links
California Climate Action Registry Urban Forest Project Reporting Protocol. – This site contains the protocol and appendices, provides a brief description, and alerts you to changes to its status.
http://www.climateregistry.org/tools/protocols/project-protocols/urban-forest.html
U.S. Carbon Dioxide Emissions from Energy Sources 2007 – Provides relatively current estimates of U.S. carbon dioxide emissions by end-use sector, such as residential, transportation, and electric power.
U.S. Emissions of Greenhouse Gases Report 2006 – Presents annual U.S. emissions for different GHGs and provides a global perspective.
Mayors Climate Protection Center – Describes the Climate Protection Agreement signed by over 850 mayors, and presents best practices, including tree planting and stewardship projects in selected cities.
U.S. Environmental Protection Agency Heat Island – presents basic information on urban heat islands, describes research and demonstration projects, and what can be done using trees.
A Guide to Street Tree Inventory Software. – presents a collection of publications to guide urban forestry professionals in the selection of a street tree inventory software program and describes those that are commercially available. [Note: info not limited to street trees].
i-Tree Software Suite v. 2.0 Users Manual- is a tool for assessing and managing community forests.
Recommended Citation
McPherson, E.G.; Simpson, J.R.; Peper, P.J.; Aguaron, E. 2008. Urban Forestry and Climate Change. Albany, CA: USDA Forest Service, Pacific Southwest Research Station.
http://www.fs.fed.us/ccrc/topics/urban-forests/
