Carbon Sequestration of Trees in City of Kitchener Parks

"The Closed Circle"

By Tara Doherty, Melanie Murphy and Riyaz Lalani

ERS 285 University of Waterloo

Table of Contents

Executive Summary

1.0 Introduction

2.0 Background

3.0 Systems 4.0 Criteria for Evaluating the System

5.0 Methodology

6.0 Results

7.0 Limitations

8.0 Conclusions

9.0 Recommendations

Works Cited




Executive Summary

A potential enhancement of the Earth's greenhouse effect is a critical environmental problem. Climatic changes could result in catastrophic effects on human economic systems and natural ecosystems.  CO2 is the most significant contributor of the radiatively active gases to the human influence on the greenhouse effect (Freedman and Keith, 1995, p.1). Because CO2 emissions are directly linked  to many economically prosperous activities, it is difficult for society to quickly accomplish large reductions in its production.

One possible strategy to partially offset emissions of  CO2 is to engage in tree planting initiatives. As trees grow, they remove CO2 from the atmosphere during the process of photosynthesis. The CO2 is fixed as organic carbon accumulating in the form of biomass. Research demonstrates that substantial carbon credits can be attained by planting large quantities of trees in urban environments (McPherson, 1992, Ip, 1996).

Our own findings suggests that between 15.7 million kg and 31.2 million kg of CO2 is removed by trees within the City of Kitchener’s parks each year. This range represents a minimum of 20% or a maximum of 40% of the City's estimated total CO2 production.

Our results reflect the CO2 that is sequestered by trees only within the City's parks. Other carbon sinks are not included in this figure, nor are other forested areas. We could suggest, therefore, that if other sinks are considered, or even if the capacity of the remainder of the City of Kitchener’s wooded areas to assimilate CO2 are addressed, the amount of CO2 sequestered will increase substantially. It is therefore evident that tree planting initiatives are an effective method of offsetting CO2 production from human sources.

1.0 Introduction

Humans are an influential ecological force and have caused an alteration in Earth's vegetation and influenced regional and global climate. Heat balance and humidity has been modified by the drainage of wetlands, diversion of rivers, and the removal of forest for grazing and crop lands; agricultural and grazing practices have increased desertification in parts of the world. Since the beginning of the Industrial Revolution, however, human impact on climate has been the most apparent. Levels of carbon dioxide (CO2) emissions into the atmosphere have been increasing exponentially, potentially altering the earth's climate (Smith, 1992).

2.0 Background

2.1 Project Rationale

Our group is undertaking this study of carbon sinks in the City of Kitchener with the goal of producing data for the carbon sequestration capability of trees in the City's parks.

2.1.1 City of Kitchener’s Role in the "20% Club"

The City of Kitchener is a signatory to an international pledge to reduce its CO2 emissions by 20% from 1990 levels, by the year 2000. This voluntary commitment, entitled Cities for Climate Protection Campaign, is a response to the Framework Convention on Climate Change, signed at the United Nations Conference on Environment and Development in Rio de Janeiro in 1992. The Campaign was initiated by the International Council for Local Environmental Issues (ICLEI) and proclaims the 172 cities involved members of the "20% Club". To fulfill their obligation, the City has concluded that they must determine the specific components of the carbon budget, the primary components being the producers and consumers of CO2.

The major sources (producers) of CO2 in the City of Kitchener include: transportation, energy and heating, for which the City has compiled CO2 production data. What is absent, however, is data concerning CO2 absorption by various carbon sinks, such as bodies of water, wetland complexes, and vegetation. Discussion with city officials revealed the compelling need for an assessment of the potential CO2 sequestration capacity of these carbon sinks in the City. All these constituents form the system around which our study will revolve, focusing on the role of trees in City of Kitchener Parks as carbon sinks. (See Figure 1).

Once an estimate of the sequestration value of Parkland trees has been determined, a comparison with the estimated total amount of CO2 that is produced in the City may suggest a need for the enhancement of carbon sinks. The consideration of the effectiveness of woodlands as a sink may indicate a potential strategy for achievement of the City's goal of a 20% CO2 emission reduction.

2.2 The Greenhouse Effect

The "greenhouse effect" is a naturally occurring, physical process by which gases in the Earth's atmosphere help to regulate the planet's surface temperature within an appropriate range for ecological processes and the functioning of organisms. Without the greenhouse effect, the surface temperature of the Earth would likely be too low for the tolerance of most organisms and ecosystems. The greenhouse effect reduces the radiative cooling of Earth, helping to keep its surface at an average temperature of 25 degrees Celsius. Essential ecological processes are thus allowed to continue efficiently (Freedman and Keith, 1995, p. 1).

Solar electromagnetic radiation is the primary input of energy to the Earth. A large portion of this solar radiation infiltrates through the Earth's atmosphere, being absorbed by the surface. To discourage an extreme build-up of temperature, the Earth disperses its absorbed energy by emitting long-wave infrared radiation. The surface temperature of the Earth is determined by the equilibrium rates at which solar energy is absorbed by its surface, and the rate at which the absorbed energy is consequently re-radiated (Freedman and Keith, 1995).
The existence of radiatively active gases, otherwise known as greenhouse gases in the atmosphere causes the naturally occurring greenhouse effect. These gases are effective assimilators in the long-wave, infrared portion of the electromagnetic spectrum. This includes the radiant energy that Earth gives off to cool itself of absorbed solar radiation. Once these atmospheric gases absorb Earth's re-radiated infrared energy, they are heated and sustain their own energy-dissipating radiation. This radiation is emitted in all directions, including back to the Earth's surface. The net effect of these energy transformations and radiation is an intervention with the cooling rate of Earth. Therefore, the Earth's equilibrium surface temperature is warmer than would occur if radiatively active gases were absent in the atmosphere (Freedman and Keith, 1995, p.2).

This process described is referred to as the "greenhouse effect," because it occurs through a physical action similar to that by which a glass-enclosed space is warmed by solar radiation.

The substantial increases of CO2 concentrations in the atmosphere are accountable for about one-half of the human enhancement of the Earth's greenhouse effect; methane, nitrous oxide and Chlorofluorocarbons are believed to compose the remainder (Freedman and Keith, 1995, p. 3).

Although the greenhouse effect is indeed a naturally occurring process, anthropogenic sources of CO2, such as the burning of fossil fuels, artificially escalate the concentration of radiatively active gases in the atmosphere. Currently there is increasing concern over the hypothesis that the elevation of CO2 emissions is leading to global climate change (Freedman and Keith, 1995, Smith, 1992, Jo and McPherson, 1995). A significant warming of the Earth's surface could have far reaching consequences. Changes in precipitation patterns and amounts and a rise in sea level could result, inducing major ecological responses to occur. Potentially devastating repercussions for biological diversity and entrenched human socio-economic systems could result (Freedman and Keith, 1995, p.3).

2.3 Previous Research

The CO2 sequestration research that we have undertaken for the City of Kitchener compliments the CO2 production data the City has compiled. The estimated values for CO2 production in the carbon budget, determined by James Moore, are baseline data which are required by all further investigations.  There have been no other CO2 sequestration studies undertaken for the City of Kitchener to our knowledge.

There have been however, studies similar to the one that we have been engaged in.  Hyun-Kil Jo and E. Gregory McPherson authored a paper entitled "Carbon Storage and Flux in Urban Residential Greenspace," also known as the "Chicago Report".  That particular study focused on two residential blocks in Chicago and the net carbon sequestration of all the vegetation and soil within the blocks.  E. Gregory McPherson has authored several papers of this type.  Studies of this type have also been completed for Toronto and Oakland.

We did refer to the Chicago study, as well other reports that examined carbon sequestration.  They were of limited use to us, since the authors of these reports did not supply enough information to replicate their work.  It was difficult to apply much of the site specific methods used in the other studies to the City of Kitchener.

We had difficulty in isolating species specific CO2 sequestration data from the previously completed studies.

2.4 Contacts

Our key contacts for this project include:

University of Waterloo

City of Kitchener ICLEI – initiator of the Cities for Climate Protection Campaign;  report GRCA – meeting, reports 3.0 Systems

Through studying the levels of CO2 production and carbon sinks in the City of Kitchener, it is evident that our system study exists at local level, while being a part of a much larger, global system in terms of CO2 levels in the atmosphere. It becomes apparent that our system is not only part of a biophysical hierarchy, being under global CO2 production and sequestration (through the permeable boundaries of our system), but also part of a social/political hierarchy. Politically, for this endeavor, the City of Kitchener is under the direction of ICLEI and alongside all the other cities who are also members of the 20% Club. The City of Kitchener also branches downward to the Parks Division, Environmental Committee and Planning Department.

3.1 System Behaviours:

One of the most important behaviours of our system to notice is the inputs (CO2 from the producers) and the function of the Carbon sinks. These components of the system are not static, that is they are always in action, involved in a complex feedback system between each other. CO2 enters into the system, where the sinks then absorb CO2 for photosynthesis, CO2 not sequestered is released to the atmosphere. Because of this feedback, the levels of CO2 in the atmosphere will fluctuate.

The other components of the system can be described nominally, including the CO2 producers, and the types and species of vegetation of which the Carbon sinks are comprised. (Our system also consists of measurable components, including: the total areas of each woodland sink and the grand total of sink area for the City, the amounts of CO2 which are being produced from which sources and the total, and then the total amount of sequestered CO2 by the sinks.) The latter will be derived from the following equation (dependent upon the sink type and its capabilities):

                   Area(ha) * Rate of Absorption (kg/C02/year) = Sequestered CO2

Strategies and Tactics of the Associated Control Systems:

The goal of the system is to balance the Carbon budget. In order to reach this goal, some strategies of the associated control systems will be as general as:decreasing CO2 production, an/or increasing the sequestration capabilities of the City's sinks (by total area, age, or sink type (e.g. - tree species)).

The outcome of our study will not be entirely conclusive in regards the carbon budget for the City of Kitchener. Due to the nature of our study there will be some potential sources of error. An opportunity for further study and refinement however, will present itself.

We will have to make several assumptions in our report: in general, we are assuming that the information we are receiving from our contacts is correct and accurate, especially in terms of numbers, whereas the original researchers have probably had to do some generalizing, as will we. For example, we will be generalizing each of Kitchener's woodlands, in categories of: dominant tree species, or whether it is a deciduous or coniferous woodland. Even though the woodlands may contain attributes of both coniferous and deciduous, in some instances (for ease of calculation of the woodland's sequestration capabilities), we will need to generalize. We will also be generalizing the age and sizes of trees in the woodland, assuming uniformity throughout each woodland.

Another potential source of error is the fact in calculating sinks we will not be counting vegetation other than trees, such as herbaceous ground cover. Again, this is due to the time limitations that we have.

In the data we have received regarding the sequestration capabilities of each species of tree, it is possible that the final numbers are the 'optimum' amounts possible by any one tree, in an ideal situation. However, there are certain factors that can alter sequestration capabilities of a tree that might not have been taken into consideration. For instance, theoretically a specific tree species could soak up 'x' amount of CO2, but age, size, and location of the tree will affect the amount possible. Regarding location, if, for example, a tree is in an industrial area, there are certain pollutants that may be in the air that could clog the stomata of the tree's leaves, thus inhibiting CO2 from entering the tree.

We have not been involved with the preliminary research that we are using (e.g. - the total CO2 production of the various sources, measuring CO2 sequestration capabilities of each species of tree, or the actual species make-up of the woodlands present in the City of Kitchener) but nevertheless, we will take these figures and apply them with greatest accuracy as is possible from our point of the project onward.

3.2 System Boundaries

Atmospheric CO2 enters the system from various sources including transportation, energy, and heating. The CO2 is sequestered by carbon sinks such as vegetation, bodies of water and wetland complexes in the system. Due to the vast differences in sequestration capabilities of distinct carbon sinks, limited time and human resources, we are narrowing the scope of our project to the impact of trees on the City's carbon budget.

Although he City receives CO2 inputs from sources outside the City, these sources will not be addressed within this study. Research will be devoted entirely to the CO2 production and sequestration within the confines of the City of Kitchener. The resulting information will enable the municipal government to gain a better understanding of their status as a producer of CO2 and how this correlates to the achievement of their objective of a 20% reduction in 1990 CO2 levels by 2000.

Two outcomes of this study are foreseeable: the City's carbon sinks could be adequate, thus removing more CO2 from the atmosphere than the City produces, or the City's CO2 production could exceed the sequestration capacity of carbon sinks with the City. In the latter case, the surplus CO2 would escape the permeable environmental boundary, becoming part of the global carbon cycle.

4.0 Criteria for Evaluating the System

To evaluate the system of carbon sinks in the City of Kitchener, it is necessary to determine the total area of tree coverage in the City. From that data, we would like to determine the amount of deciduous and coniferous trees, assuming that each type of tree and perhaps each species will sequester varying amounts of CO2 . It would be valuable to determine the species dominance of trees within areas of the City, because if it becomes apparent that tree planting initiatives would assist in the sequestration of CO2 , recommendations could be made regarding the species of trees to plant. Also, data on the average number of trees planted in the City each year would be of assistance, because this information, along with the study results, could aid the City in determining
future trends in CO2 emissions.

Based on the findings of the study, we will be able to indicate how successful the City is thus far in reaching the 20% reduction objective. Although we are not considering the intake capabilities of all of the various sinks within the City, analysis of the tree sinks does provide a starting point for indicating whether the existing carbon budget is balanced. It is possible, however, that there will be a sizable deficit or surplus of CO2 . The study results should therefore demonstrate the effectiveness of trees as a carbon sink.

5.0 Methodology

Throughout the project phases, there were various steps that were taken to obtain background information and data needed for calculating the sequestration of CO2 in Parkland trees.

5.1 Collection of Data

Data collection progressed as follows:

5.2 Calculations

The calculation of CO2 sequestration by the City's parks was a task that required investigation into various resources. We were able to use two sources of estimates of the average CO2 sequestration rates of trees.  The first source was from the ICLEI Background Paper "Urban Forestry and Community Cooling."  It stated that the "average large species tree in Toronto" sequesters 172 kg of CO2 each year.  The second source was from the Journal of Arboriculture November 1993; it corroborated the number provided by the ICLEI paper.  The Journal estimated that a 12.2m deciduous tree in Fresno, California, absorbed 172 kg of CO2 each year.  The ICLEI paper also reported that large tree species with an average age of 50 years or higher, sequestered 341.1 kg of CO2 per year.

To arrive at the amount of CO2 sequestered by the trees in each park in the City of Kitchener, we multiplied the number of trees we estimated to be in the park by a value representing the amount of CO2 sequestered by the tree.  This was done twice to provide perspectives using both data sources, once using the sequestration value of 172 kg/CO2/year and once by using the sequestration value of 341.1 kg/CO2/year.   We then took the sum of all the CO2 sequestered by the trees in the City parks.

5.2.1 Assumptions and Conversions

David Schmitt, one of the authors of the Woodland Management Report, estimated that there were 100 trees per acre in the wooded areas of the City's parks.  We converted that tree density estimate into hectares; we estimate that there are 247 trees per hectare in the wooded areas of the City's parks.  Mr. Schmitt also said that the average age of trees in the City's parks was about 80 years.

Some of the CO2 sequestration data was expressed as the amount of carbon sequestered.  In those cases we converted "carbon sequestered" to "carbon dioxide sequestered" using a conversion ratio of 1 kg of carbon = 3.68 kg of carbon dioxide.  We arrived at this conversion ratio by dividing the atomic weight of CO2 by the atomic weight of Carbon.

CO2 = 44  and C = 12    44/12 = 3.68 

6.0 Results
According to James Moore of the City of Kitchener the major sources of CO2 in the City: natural gas, electricity, cars and trucks, produce about 74,000,000 kg of CO2 each year.  We calculated that the trees in the City's parks sequester between 15.7 and 31.2 million kg of CO2 each year.  Trees in the City's parks absorb 20-40% of the CO2 produced by the City.

7.0 Limitations

In our study we did not count trees and vegetation outside of City parks.  Trees on private property, boulevard trees, shrubs, wetlands and bodies of water were not included in our study.

We were also limited by the quality and nature of our data. Some of the data we received was from secondary sources and we trusted that the information was accurate.

Some of the data that we used were from studies conducted outside of the City of Kitchener. We were required to have averaged outcomes, not exact numbers because it was not feasible in the time constraints of our study to determine exact area, density and age of trees in the City's parks.

The sequestration rates that we used, do not account for tree mortality.  A dead tree becomes a net source of CO2.

8.0 Conclusions

Our study has revealed that trees in the City of Kitchener’s Parks are a significant and valuable carbon sink.  They sequester between 20-40% of the CO2 produced by the City's major CO2 sources.

9.0 Recommendations

Based on the results derived from our calculations on CO2 sequestration for the City of Kitchener, we have compiled the following list of recommendations.

9.1 Refining the Study

9.2 Establishing a Trend 9.3 Actions to be Taken
Works Cited

Dwyer, John F., E. Gregory McPherson, et al.  1992.  "Assessing the Benefits and Costs of the Urban Forest."  Journal of Arboriculture.  18(5): 227-234.

Freedman, Bill and Todd Keith. "Planting Trees for Carbon Credits".  Prepared for the Tree Canada Foundation.  Halifax: Dalhousie University, August 1995.

Ip, David W.  1996.  "Community Tree Planting: Early Survival and Carbon Sequestering Potential."  Journal of Arboriculture.  22(5): 222-228.

Jo, Hyun-Kil and E. Gregory McPherson.  1995.  "Carbon Storage and Flux in Urban Residential Greenspace."  Journal of Arboriculture.  45: 109-133.

Raven, Peter H, Ray F. Evert, and Susan E. Eichhorn.  Biology of Plants (5th ed.).  New York: Worth Publishers, 1992.

Smith, Robert Leo.  Elements of Ecology (3rd ed.).  New York: HarperCollins Publishers Inc, 1992.

Urban Forestry and Community Cooling – A Background Paper (ICLEI).  Prepared by: Torrie Smith Associates with ICLEI.  Prepared for: Toronto Atmospheric Fund. Ottawa, March 1997.


"City of Kitchener Woodland Inventory and Evaluation" (map).  Kitchener: Parks and Recreation Department, Design/Development Section, February 1994.

Dwyer, John F., E. Gregory McPherson, et al.  1992.  "Assessing the Benefits and Costs of the Urban Forest."  Journal of Arboriculture.  18(5): 227-234.

Ford, Chris.  Personal and Telephone Interviews.  May-August 1997.

Freedman, Bill and Todd Keith. "Planting Trees for Carbon Credits".  Prepared for the Tree Canada Foundation.  Halifax: Dalhousie University, August 1995.

Greenhouse Gases, The.  Nairobi, Kenya: United Nations Environment Programme, 1987.

Hengeveld, Henry.  "Understanding Atmospheric Change: A Survey of the Background Science and Implications of Climate Change and Ozone Depletion."  A State of the Environment Report.  Canada: Authority of the Minister of the Environment, 1991.

International Council for Local Environmental Initiatives (web page).

Ip, David W.  1996.  "Community Tree Planting: Early Survival and Carbon Sequestering Potential."  Journal of Arboriculture.  22(5): 222-228.

Jo, Hyun-Kil and E. Gregory McPherson.  1995.  "Carbon Storage and Flux in Urban Residential Greenspace."  Journal of Arboriculture.  45: 109-133.

Kay, Paul.  Personal Interviews.  May-August 1997.

Lamb, Larry.  Personal Interview.  26 June 1997.

Leggett, Jeremy K., ed.  "Global Warming: The Greenpeace Report."  Toronto: Oxford University Press, 1990.

McPherson, E. Gregory and Rowan A. Rowntree.  1993.  "Energy Conservation Potential of Urban Tree Planting."  Journal of Arboriculture.  19(6): 321-331.

Miller, G. Tyler.  "Living in the Environment: An Introduction to Environmental Science".  Belmont, California: Wadsworth, 1990.

Moore, James.  Personal and Telephone Interviews.  May-August 1997.

Murphy, Stephen.  Personal Interview.  12 June 1997.

Raven, Peter H, Ray F. Evert, and Susan E. Eichhorn.  Biology of Plants (5th ed.).  New York: Worth Publishers, 1992.

Schmitt, David.  Telephone Interview.  18 July 1997.

Schmitt, David.  Woodland Management Program.  Kitchener:  Forestry Section, Parks Operations, March 1995.

Smith, Robert Leo.  Elements of Ecology (3rd ed.).  New York: HarperCollins Publishers Inc, 1992.

Urban Forestry and Community Cooling – A Background Paper (ICLEI).  Prepared by: Torrie Smith Associates with ICLEI.  Prepared for: Toronto Atmospheric Fund. Ottawa, March 1997.

Woodland Inventory and Evaluation for Areas Outside Current Development Lines. Kitchener: Parks and Recreation Department, Design/Development Section,
February 1994.


Appendix A:  Calculations

Wooded Area (Hectares) 
Number of Trees 
CO2 Seq. Rate 172.0 kg/CO2 
CO2 Seq. Rate 341.1 kg/CO2 
Concordia Park
Lakeside Park
Mausser Park
Meinzinger Park
Raddatz Park
Breithaupt Park
Bridgeport (Sportsfield)
Karen Witzel Park
Lancaster Business Park
Springwood Park
Georgian Park
Stanley Park
Idlewood Park
Morrison Park Extension
Prospect Park
Springmount Park
Stonegate park
Alpine Park
Country Hills Park
Steckle Woods
Strasburg Woods
Wilson Park
Brigadoon Park and Pond
Homer Watson Park
Millwood Park
Pinnacle Hill Area
Pioneer Tower Area
Tilt's Bush
Upper Canada Park
Willowlake Park
Cedar Crest Park
Lorilee Park
Trailview Park
Waldau Woods
Westheights Park
Monarch Woods

  Appendix B: Major Carbon Dioxide Sources in the City of Kitchener
Carbon Source kg/CO2/Year
Natural Gas

Appendix C:  Global Carbon Cycle Systems Diagram