Good
Policy and Good Business:
Communities’ Solutions for a Hot Issue
Call to Action on Air
Quality
Low
Tech Solution
Cool
Communities and the Green Industry
Rapid growth
in many areas of the Southeast is causing growing pains for the
infrastructure. Air quality suffers, with many counties fast approaching
or already in a non-attainment status. Increased impervious surface
cover causes serious stormwater management problems with increased
polluted runoff into our streams and waterways. It is not uncommon
for developers to face stringent restrictions or even moratoriums
in some areas as the infrastructure is stretched to the limits
of its capacity by the increased growth. Forested and highly vegetative
land cover is being replaced with built structures, roads, subdivisions,
shopping malls, office parks and all the supporting infrastructure
needed to support urban sprawl. These man-made surfaces, particularly
large horizontal expanses of dark surfaces like commercial roofs
and pavements, absorb the sun’s rays, causing both surface temperature
and overall ambient air temperature in urban areas to rise, creating
heat islands. Often urban temperatures are as much as 10 degrees
F higher than outlying areas with significant tree canopy and
less developed space.
Figure
1
Urban heat
islands have several adverse effects on communities. Increased
pollutants in the air from cars and other sources coupled with
the increased heat, create smog and ground level ozone – harmful
to the environment and our health. As the summer heat increases,
so does energy use for air conditioning at home, work and in our
cars. This causes increased power plant emissions, not to mention
higher energy bills. Heated run-off from impervious surfaces carries
pollutants into our streams and tributaries, degrading water quality
and affecting heat-sensitive species. In addition, rapid runoff
from roadways, parking lots, and buildings can cause erosion and
flooding while carrying increased sediment loads to streams.
Innovative
studies in Atlanta and Houston are documenting the relationship
between excess urban heat and air pollution. This effort to incorporate
land cover into an air pollution control strategy has important
implications for the green industry. Scientists from several different
disciplines are testing strategies that would incorporate more
tree canopy and a reduction of dark impervious surfaces that absorb
solar radiation and store excess heat. If the air quality models
are validated, state environmental officials could use tree plantings
and forested areas as part of an approved air pollution control
strategy.
The fundamental
and over-arching objective of a design strategy based on Cool
Communities principals is to construct the built environment in
such a way as to mimic the natural environment in terms of heat
physics and the hydrologic cycle. In practical terms this means
protecting and planting trees and reducing “heat sinks” by using
lighter colored roofing and paving. “Green roofs” can also be
part of a Cool Communities design strategy. Changing the land
cover in a large urban area is an ambitious task that will take
time, but is both good environmental policy and good for business.
Green industry support for this program is essential.
Cool Communities
is a non-profit program that has been advocating these sustainable
design concepts since 1994. The independently funded program is
a descendent of a pilot program initiated in 1992 and originally
funded by the U.S. Department of Energy and U.S. Environmental
Protection Agency. Since 1997, NASA’s Global Hydrology and Climate
Center in Huntsville, Alabama, has participated as the research
component for the program. NASA has provided valuable infrared
satellite imagery and data though its heat island studies which
focus on the impact of land-use change on urban temperature and
air quality. The program also applies the research products of
the Urban Heat Island Research project of Lawrence Berkeley National
Laboratories and the Heat Island Reduction Initiative project
of the U.S. Environmental Protection Agency. This diverse group
of government, private industry, non-profit, and community leaders
serves as a resource to develop stronger business and community
based coalitions to implement Cool Communities concepts.
Call to Action on Air Quality
As cities
across the Southeast are faced with non-attainment of EPA’s air
quality standards, control strategies have focused on reducing
emissions- mainly nitrogen oxides (NOx) and volatile organic compounds
(VOCs). It is evident, however, that even with stringent emissions
controls, we need to do more. Because NOx and VOCs react with
heat and sunlight to form ground level ozone (O3), the newest
approach in air quality is to reduce excess urban heat. NASA,
in partnership with Georgia Environmental Protection Division,
Georgia Regional Transportation Authority, Atlanta Regional Commissions
and Cool Communities, is currently investigating ways of incorporating
heat island mitigation strategies into a new air quality model
– one that combines emission control with land cover thermal characteristics.
A similar study funded by U.S. EPA and using the research of Lawrence
Berkeley National Laboratories is underway in the Houston, TX,
area.
Results from
computer modeling by researchers at the Lawrence Berkeley National
Laboratory indicate that each 1 oF rise in temperature over 70
oF increases the potential for ozone formation by approximately
3% (USDOE, 1996). In fact, it now seems likely that excess urban
heat may be responsible for up to 30% of our ground level ozone.
Research shows that use of lighter heat-reflective materials for
roofing and paving along with careful planting of trees could
lower the average summer afternoon temperature in some cities
by as much as 5 degrees F, cutting the need for air conditioning
by 18 percent and even reducing air pollution. For a city the
size of Los Angeles, a reduction in urban temperatures of approximately
3 oF is estimated to produce air quality benefits roughly equivalent
to replacing a city’s entire fleet of gas-powered cars with electric
vehicles.
NASA’s Project
ATLANTA has generated the most remarkable mapping of the Atlanta
region imaginable. A recently granted extension of that project
will produce even more data. A new satellite, QuickBird II will
use some of the most sophisticated photographic and infrared equipment
to produce detailed maps. Computer enhanced, high-resolution imagery
will produce very precise details that can differentiate land
cover and produce a distinct heat signature for every structure
in the built environment. In the near future, planners and policy
makers may be able to meet air pollution goals by increasing the
tree canopy and albedo (reflectivity) of certain large developments
of regional impact. Reducing the amount of impervious land cover
through the use of innovative design strategies like Green Roof
technology and porous paving will help developments to more nearly
resemble natural land cover
Low Tech Solution
Urban shade
trees have been called the "low tech" solution to energy
conservation. Because leaves intercept and store water, trees
help to slow the movement of stormwater, lower total runoff volume,
and reduce flooding. Tree roots hold soil in place so it cannot
easily be washed away by wind or water, preventing the transport
of sediment and chemicals into streams. Trees and other vegetation
cool ambient air temperature through evapo-transpiration. A single
properly watered tree can "evapo-transpirate" 40 gallons
of water in a day, offsetting the heat equivalent to that produced
by one hundred 100-watt lamps burning eight hours per day. By
providing cooling shade, strategically placed trees around buildings
and parking lots can reduce energy costs for cooling and mitigate
the impact of heat absorbing parking lots, not to mention the
aesthetic benefits provided to the urban streets. "The net
cooling effect of a young, healthy tree is equivalent to ten room-size
air conditioners operating 20 hours a day." - U.S. Department
of Agriculture.
Tree leaves
and roots act as natural filters of air and water (rain and ground),
removing particulate matter and pollutants. Leaves filter the
air we breathe by removing dust and other particulates. In the
process of photosynthesis, leaves absorb carbon dioxide in addition
to other air pollutants such as ozone, carbon monoxide, and sulfur
dioxide, and give off oxygen.
Cool Communities and the Green
Industry
Cool Communities’
strategies of cool roofing, cool paving, and urban shade trees
work together as a sustainable design "system," thus
greatly increasing their effectiveness. While each of these measures
presents separate challenges, tree canopy has the broadest implications.
It is arguably the easiest to understand and is the most action-oriented.
These measures offer a cost-effective and innovative approach
to pollution prevention, providing tremendous benefit for minimal
cost. This approach is non-regulatory; does not require behavior
modification, can be implemented for new development or as part
of a normal maintenance cycle. In addition it is energy efficient
and helps to create a more pleasant urban environment.
Understanding
and support from the green industry is essential to make Cool
Communities successful. The leadership of the Southern Nursery
Association has enthusiastically endorsed this program and expects
to help develop some marketing and public awareness activities
to promote Cool Communities. This program is a rare opportunity
to support a sensible, effective environmental policy and a good
business strategy for our industry. Our industry and our support
for Cool Communities is part of the solution.
For more information
about Cool Communities and ongoing research, visit their web site
at www.coolcommunities.org
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