Written by Maria Cahill
Sustainable Site Specialist
Green Girl Land Development Solutions
I recently started a discussion on the NPSINFO listserv regarding the link between air
quality (not just greenhouse gas emissions, but also particulates), energy (which is
mostly still generated from dirty sources like coal and nuclear power) and stormwater
and got this great link on urban forests and climate change.
http://www.fs.fed.us/ccrc/topics/urban-forests/
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)
This is a link to the modeling software described below that, in addition to modeling
GHG sequestration, can calculate the energy savings for trees that are strategically
placed on the site.
http://www.fs.fed.us/ccrc/topics/urban-forests/ctcc/
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 sixteen United States climate
zones. Once the ctcc screen shot 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 650-1000 street trees
representing approximately 20 predominant species in each of the sixteen 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 2011, this version will be replaced
by a Web-based version with greater functionality.
