Preliminary Assessment
Assessment of
of the
the Tornado
Tornado Effects
Effects on
on Residential
Residential
Preliminary
Street Tree
Tree Canopy
Canopy Cover,
Cover,Temperature,
Temperature, and
and Humidity
Humidity
Street
November 2011
USDA Forest Service
Northern Research Station
TREE CANOPY LOSS IN THE TORNADO
IMPACT ZONE WAS EXTENSIVE, WITH
MANY LARGE SHADE TREES DESTROYED.
The June 2011Massachusetts tornado profoundly
altered the landscape over a wide geographic area.
On June 1, 2011 a series of
tornadoes ripped through Western
Massachusetts, and included the
according to the National Weather
Service. The most severe tornado
was the EF-3, on the Enhanced Fujita
killing three people and injuring 200.
In Springfield, the tornados impacted
city’s South End, Upper Hill, Metro
second strongest tornado ever
recorded in Massachusetts, with wind
speeds estimated at 136 to 165 mph,
Damage Classification Scale, that
carved a half-mile-wide path for 39
miles, from Westfield to Charlton,
Center, Six Corners, East Forest Park
and Sixteen Acres neighborhoods.
CA NO PY LO SS
TRE E FAI LUR E
STRUC TURE DAMA GE
Tornado Effects on Residential Street Tree Canopy Cover,
Temperature, and Humidity: Introduction
Introduction
Recent modeling studies have reported
on the relationships between residential
trees and urban micro-climate with
subsequent impacts on energy use for
heating and cooling (McPherson et al.
1997, Simpson and McPherson 1998,
Maco and McPherson 2003, McPherson
et al. 2005). However, there are few
studies that empirically quantify the
relationship between the presence,
abundance, and type of residential trees
and local micro-climate (Heisler and
Brazel 2010).
In Sacramento, CA, tree cover density
was negatively correlated with local
wind speed and with cooling degree
APPROXIMATELY 1.4 MILLION
POUNDS OF SEQUESTERED
CO2 HAS BEEN LOST
days (Sailor et al. 1992). In Baltimore,
MD, increasing tree cover generally
resulted in cooler temperatures during
the daylight hours (Heisler et al. 2007).
On June 1, 2011, an EF-3 tornado
traveled a 39-mile track across southcentral Massachusetts (http://
www.erh.noaa.gov/box/sigevents/
jun01_2011_summary.php). The
tornado’s track crossed the city of
Springfield, MA, impacting several
neighborhoods and damaging over 480
buildings and 13,000 public trees, with
an estimated cost of over $106 million.
CONTEXT
IMPACT ZONE
This event created an opportunity to
empirically measure the effects of the
loss of neighborhood trees on streetside micro-climate (temperature,
relative humidity). We implemented a
preliminary study to estimate the
impact of the tornado on street trees
and micro-climate of the impact zone.
TREE LOSS
Map 1. New England regional context
C ANOPY DAMAGE
Map 2. Massachusetts map, with
Springfield identified in red, and Hampden
County noted in pink.
C ANOPY LOSS
Tornado Effects on Residential Street Tree Canopy Cover,
Temperature, and Humidity: Study Area and Methods
‘iBUTTON’ MONITOR
S T U DY A R EA
IN THE F I E L D
Figure 1. Tornado Impacted (red box) and unaffected (yellow box)
neighborhoods and forested Dan Baker Cove Park, East Forest Park,
Springfield, MA
PLACING MONITOR
MONITOR PLACEMENT
Study Area and Methods
We measured air temperature and
relative humidity in two adjacent
(0800 hrs), and afternoon (1600 hrs)
for the duration of the preliminary
study (30 Aug – 26 Sep 2011).
residential neighborhoods in the East
Forest Park area of Springfield (Fig. 1).
Tree canopy cover was measured in the
four cardinal directions at each data
Data loggers (iButton Hydrochrons®)
were placed in two blocks of three
streets in the tornado damaged area.
logger location using a spherical
densiometer. Information on the
tornado damage to privately-owned
Matching data loggers were placed in
two blocks of the same or paired
residential trees of the study area is
being assessed using aerial
streets in an unaffected neighborhood
just to the south of the tornado track
(Fig. 1). A single data logger was placed
photographs, which were taken by the
Forest Service following the tornado,
and i-Tree Canopy.
the forested Dan Baker Cove Park, just
north of the tornado damaged area.
Paired, daily mean temperature and
relative humidity data were analyzed to
Data loggers were enclosed in windowscreen envelopes and hung by wires
from street signs. Temperature and
C ANOPY ASSESSMENT
relative humidity were recorded three
times a day; night (0000 hrs), morning
assess the effects of the tornado
damage to residential trees on streetside micro-climate.
Tornado Effects on Residential Street Tree Canopy Cover,
Temperature, and Humidity: Results and Discussion
Results
The tornado nearly eliminated street-side tree canopy cover, from an average of 44% canopy cover in the control,
unaffected neighborhood to less than 1% in the tornado impacted neighborhood (Table 1). Daily mean morning and
afternoon temperatures were typically greater in the tornado impacted neighborhood than the unaffected neighborhood
and forest site, but were similar at night (Fig. 2). Daily afternoon temperatures were intermediate between the tornado
impacted neighborhood and forest site in the unaffected neighborhood (Fig. 2). The average morning and afternoon
temperature increased between 1-2ºC in the tornado impacted neighborhood, compared to the unaffected neighborhood
(Table 1). Night-time temperatures were only slightly less in the tornado impacted neighborhood than the unaffected one
(Table 1). Daytime temperatures at the single forest site were cooler than either of the residential sites and nighttime
temperatures were similar among all sites (Table 1). Mean daily humidity was similar in the tornado impacted and
unaffected neighborhoods, but typically greater in the urban forest (Park) site. Mean percent relative humidity were
slightly less in the tornado impacted neighborhood than unaffected neighborhood in the morning and afternoon, and
slightly greater in the nighttime (Table 1).
Discussion
The results of this preliminary study indicate that there is a obvious difference in canopy density and the micro-climate
characteristics between the tornado impact zone affected neighborhood and nearby areas that were not affected by the
storm event. The noted difference in afternoon daily temperatures between the two areas provides preliminary, quantitative
findings that supports the antidotal testimony from residents of the impacted
affected area, relative to the increased use of air-conditioning units, personal
Urban Heat Isla nds
comfort levels, and an overall increase in energy costs in July and August 2011.
Further study of this effect of a change in residential micro-climate is necessary to
t
hea
n
urba
of
tion
Imp leme nta
quantify any real relationships between energy costs in 2011, compared to preislan d (UHI ) mit igat ion
tornado summer periods and the loss of residential trees and resulting change in
strategies such as increase d
micro-climate.
vege tati ve cove r can reduce the
The loss of tree canopy cover following the tornado correlates with comments
imp acts of biophysical haz ards
by
residents in the impact zone, who report that the neighborhood lacks any
in citie s, inclu ding heat stre ss
shade and seems hotter and is noisier than in the past. It was noted during the
related to elev ated
site visits that there is a limited variety of songbirds seen or heard in the
tem perature s, air pollu tion and
tornado impact zone compared to the unaffected neighborhood.
asso ciated publ ic hea lth
It appears that the tornado greatly impacted the street-side tree canopy and
effe cts. Such strategies also
micro-climate, the urban bird community, and the overall appeal of tree-lined
can lowe r the dem and for airstreets and large residential shade trees. The proposed planting of new trees,
condition ing-related energy
which is intended to produce significant benefits over time, provides a unique
producti on.
opportunity to develop a long-term monitoring study within the tornado
5
200
al.
et
cki,
Sole
impact zone. The implementation of a scientific study will provide information,
data, and findings from an urban landscape that is undergoing dramatic change,
starting from near total tree loss to future recovering of tree canopy cover. The
study of past costs and benefits, along with closer examination of micro-climate impacts, and finally, the monitoring of
newly planted trees in the impact zone will provide relevant, scientifically-based information for urban foresters, planners
and the scientific community.
IM PACT S
Table 1. Mean street-side temperature (ºC) and percent relative humidity (RH) by time of
day and mean percent tree canopy cover in tornado impacted and unaffected residential
neighborhoods and from a single urban forest site, East Forest Park, Springfield, MA, 30 Aug
– 26 Sep 2011.
Figure 2. Daily street-side temperatures (ºC) by time of day,
East Forest Park, Springfield, MA, 30 Aug – 26 Sep 2011.
Literature cited
Heisler, Gordon M. and Brazel, Anthony. J. 2010. The urban physical environment: temperature and urban heat islands. Pgs.
29-56. In: Aitkenhead-Peterson, J. and Volder, A. (Eds.) Urban Ecosystem Ecology. American Society of Agronomy,
Agronomy Monograph 55.
Heisler, Gordon, Walton, Jeffrey,Yesilonis, Ian, Nowak, David, Pouyat, Richard, Grant, Richard, Grimmond, Sue, Hyde, Karla,
and Bacon, Gregory. 2007. Empirical modeling and mapping of below-canopy air temperatures in Baltimore, MD and
vicinity. In: Proceedings of the 7th Urban Environment Symposium. American Meteorlogical Society, San Diego, CA.
Maco, Scott E. and McPherson, E. Gregory. 2003. A practical approach to assessing structure, function, and value of street
tree populations in small communities. Journal of Arboriculture 29: 84-97.
McPherson, E. Gregory, Nowak, David, Heisler, Gordon, Grimmond, Sue, Souch, Catherine, Grant, Rich, and Rowntree,
Rowan. 1997. Quantifying urban forest structure, function, and value: the Chicago Urban Forest Climate Project. Urban
Ecosystems 1: 49-61.
McPherson, Greg, Simpson, James R., Peper, Paula J., Maco, Scott E., and Xiao, Qingfu. 2005. Municipal forest benefits and
costs in five US cities. Journal of Forestry 103: 411-416.
Sailor, David J., Rainer, Leo, and Akabri, Hashem. 1992. Measured impact of neighborhood tree cover on microclimate.
Pgs. 149-157. In: Proceedings of the 1992 ACEEE Summer Study on Energy Efficiency in Buildings.Volume 9. American
Council for an Energy-Efficient Economy. Washington, D.C.
Simpson, J.R. and McPherson, E.G. 1998. Simulation of tree shade impacts on residential energy use for space conditioning
in Sacramento. Atmoshpheric Environment 32: 69-74.
Solecki, W.D., Rosenzweig, C., Parshall, L., Pope, G., Clark, M., Cox, J., and Wiencke, M.. 2005. Mitigation of the heat island
effect in urban New Jersey. Global Environmental Change, Part B: Environmental Hazards. 6:39-49.
Project Study Team
David V. Bloniarz, Ph.D.
Dr. Bloniarz is an Urban Forester with an extensive background in urban forest management and landscape design.
Presently Dr. Bloniarz is project coordinator of the USDA Forest Service Northern Research Station’s Urban
Natural Resources Institute, located at the University of Massachusetts/Amherst. [email protected]
Robert T. Brooks, Ph.D.
Dr. Brooks studies the ecology of ephemeral or "vernal" pools of northeastern forests. His current research includes
study of the effectiveness of Massachusetts forestry Best Management Practices and Conservation Management
Practices for vernal pools and and projected climate change effects on the hydrology and ecology of vernal pools.
[email protected]
For more information, contact the UF Forest Service Northern Research Station
http://www.fs.fed.us/ne/ 610-557-4017