Updated letter from Kohane 11-11-22
Dear Mayor Elisa and City Council Members,
We are re-sending our earlier table in a pdf format. We noticed that the excel file stored in our
previous letter, has not been viewable. This is now attached in this document with some
additional summary and charts to help visualize what the data found in the first table titled
“Tree Function 581 Fox Hill Drive” means.
Value of Trees Tagged on 581 Fox Hill Drive, Chanhassen
The table titled “Function of Trees 581 Fox Hill Drive” is a way to give a fuller description and to
visualize, the ecological goods and services that the 61 mature trees tagged for removal on this
site provides. Included are some additional charts with an explanation, of the individual
functions that each tagged tree provides. In each chart, there is a noticeable increase in the
productivity of both the Northern Red Oaks and the Sugar Maple trees, as they reach a certain
age and maturity. At age 80, 100 or 120 years, both the Oaks and Sugar Maples, increase their
capacities to absorb carbon, and to release oxygen and moisture into the atmosphere, as well
as cooling, and increased productivity continues as these trees age. Oaks have a life span of 400
years, and Sugar Maples 350 years. Oaks are one of the best species for absorbing carbon, with
large canopies, dense wood, and a long lifespan. As Oaks capacity for carbon absorption
(sequestration) wanes as they become very old, the enlarged leaf canopy makes compensation
for this, and so continues these trees capabilities.
On this location there are an additional 139 trees (53 mature oaks & 69 sugar maples) most of
these trees are the same age and capacities, as those trees tagged for removal. While individual
trees work as a carbon sink, the trees’ capacity to draw and absorb moisture and rain (biotic
pump), and to sequester carbon, is enhanced and becomes even more efficient, when trees
remain intact, such as a woodland within a developed ecosystem. In addition, this woodland
becomes more efficient in function, because of the interconnected relationship with the
wetlands, and both the trees and wetland are sustained through the groundwater flow.
It is common practice, that when woodlands, ecosystems, and wetlands, do not have monetary
value assigned to the functions they provide, then these functions usually go unseen, they are
not valued or accounted for in the decisions related to deforestation and development, and
their ecological function and the role they play, in sustaining life, becomes trivial and
expendable. Without an understanding and inclusion of these principles in actions that can
affect the environment, incomplete decisions are made, and unsound environmental practices
persist.
Understanding Table “Function of Trees 581 Fox Hill Drive.”
All calculations provided are measured as of the current age of the trees, tagged to be
removed.
DBH in inches refers to the diameter of each tree.
Growth Factor is the annual rate of growth for each tree species. By multiplying the diameter
by the growth rate, this gives an estimated age for each tree (10” sugar maple X 4=40 years).
The trees circumference can also be calculated, once these metrics have been determined,
which also serves as an indicator of the tree’s estimated age, maturity, and productivity.
Approximate Life Span. This calculation gives an estimated lifespan of each tree species.
Northern Oaks lifespan is 400 years, and Suga Maples is 350 years. In obtaining the lifespan, this
helps to calculate estimates of the future ecological productivity of each species, and as they
mature and through the duration of their lifespan.
In addition, six (6) ecological tree functions are identified, calculated., and considered most
vital in this table.
Carbon Absorption (sequestration) is calculated in tons. This refers to the volume of carbon the
Oaks and Sugar Maples can absorb and retain, and this is measured in tons.
Oxygen Produced over time in tons. As these trees absorb carbon, and retain this in their
trunks, bark, and leaves, they also release oxygen into the atmosphere, creating fresh air. In the
charts, you will notice that as each tree reaches a certain age (80, 100, 120 years), their capacity
to release oxygen also increases dramatically, and continues throughout the lifespan.
Gallons of Water Evaporation. Each tree listed releases moisture into the atmosphere, through
evaporation. This is measured in gallons.
Cooling Effect in Days. This refers to the cooling effect trees contribute to balance the heat in
the atmosphere and is measured in days.
Mileage From Travel Negated in Plane. This refers to the amount of carbon emissions created
by air (and car) travel, that is absorbed (sequestered) by trees, from the atmosphere.
Number of People to Breathe. This refers to the amount of oxygen (clean air) that these trees
release into the atmosphere, enabling humans to breathe and stay alive. (We found this metric
difficult to understand, because it was not clear if this measures individual breaths or refers to
the number of people who breathe oxygen produced by these trees. However, we included this
measure and related calculations of productivity, because this is perhaps one of the trees’ most
vital functions in sustaining life.)
Some Additional Information for Consideration
Wetlands act as sponges that ameliorate droughts by storing water and releasing it to maintain
river flows, long after the rain ceases
Forests and woodlands soak up excess rainwater, preventing runoffs and damage from
flooding. By releasing water in the dry season, forests and woodlands can also help clean water
and mitigate the effects of drought.
An Additional Concern
While attempts have been made within the housing development proposal, to counteract the
removal of 61 mature trees, and for these to be replaced with the planting of 22 young trees,
this is not a balanced exchange of good and services. The 61 mature trees tagged for removal,
have already entered and begun the most productive period of their lives.These trees are
already working at optimum function, absorbing tons of carbon, releasing tons of oxygen,
absorbing harmful nutrients, releasing moisture into the atmosphere through evaporation,
balancing heat in the atmosphere through cooling, working as an efficient carbon sink, and
biotic pump drawing moisture and rainfall. Whereas, these lovely young trees are at the
beginning of their lives, and on the journey of maturation and full production of services. But
this maturation will take 50 years. Therefore, this is not a balanced exchange. There will be a 50
deficit of ecological output and services.
Final Summation
Given the provided information, it is best practice to leave these woodlands intact, as a highly
productive, efficient and refined ecosystem. These woods and wetlands are a highly efficient
factory, producing ecological and biological energy, and creating and producing volumes of vital
services, and at a massive rate. To intrude upon and to do damage to these woods and
wetlands, is unsound practice, and is an environmental and personal travesty. These woods and
wetlands are an asset for locals, visitors and for resident wildlife, and for future generations.
Forever preserving and protecting these woods and wetlands and designating as a land
heritage is the altruistic, and most sound course of action, and is the best option.
Table 1
Data Visualizations
Chart 1
.
This plot serves to illustrate the difficult to understand function that occurs when trees reach maturity
(provide data for maturity of tree). Data represents the critical ecosystem services provided by mature
Oak trees. As seen above, once the tree reaches an age of 100 years or more, the function increases
dramatically. The trees destined for removal from the 581 Fox Hill Drive development are well over the
age of 100 years so these are trees operating at peak efficiency, conducting critical services that would
not be replaced by planting 22 saplings due to the time it takes for trees to reach maturity. This is an
important reality for the situation of the 581 Fox Hill lot. Note that these services can be transformed
into monetary terms, meaning that from an economic standpoint, mature trees are highly valuable in
their role within the ecosystem and are economically valuable in their ability to offset carbon dioxide
emissions and produce oxygen for us to breathe. -----
The plots below represent the same effect, as the tree ages and reaches maturity, its capacity to provide
critical services increase.
Chart 2.
0
500
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0 20 40 60 80 100 120 140Value in tonsAge of Trees
Age of Tree versus Oxygen and Carbon
Oxygen Produced Carbon Stored
Chart 3.
Chart 4.
0
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0 20 40 60 80 100 120 140Water Released in TonsAge of Tree
Water release into atmosphere by
evaporation
0
20
40
60
80
100
120
0 20 40 60 80 100 120 140Cooling EffectAge of Tree
Cooling Effect
Chart 5.
0
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6000
0 20 40 60 80 100 120 140Miles NegatedAge of Tree
Mileage negated in a Commercial Airplane
0
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1000000
1500000
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2500000
0 20 40 60 80 100 120 140Breaths ProducedAge of Tree
Number of breaths produced