Urban sprawl reduces annual photosynthetic production/High in the Sky, NASA 'Heat Hunters' Combat Urban Phenomenon (Forwarded)
Andrew Yee
Goddard Space Flight Center, Greenbelt, Md. Feb. 21, 2000
Lynn.Ch...@gsfc.nasa.gov
(Phone: 301-286-5017)
RELEASE NO: 00-23
URBAN SPRAWL REDUCES ANNUAL PHOTOSYNTHETIC PRODUCTION
A study of the impact of urbanization and industrialization over the past
seven years using satellites shows that annual photosynthetic productivity
can be reduced by as much as 20 days in some areas where urbanization is
intense, not unlike turning the lights off in a greenhouse during the
growing season.
The study also reveals that urbanization may be creating vast heat islands
that can actually lengthen the growing season, but do not improve the
productivity of the land.
NASA Goddard Space Flight Center (Greenbelt, Md.) researcher Dr. Marc L.
Imhoff presents his findings during a news media briefing at the 2000
American Association for the Advancement of Science (AAAS) Annual
Meeting at the Marriott Wardman Park Hotel (Washington, D.C.) on Monday,
Feb. 21 at 3 p.m. in the Wilson Room.
According to Imhoff's research, urbanization and industrialization have
resulted in the development of mega-cities and urban and suburban sprawl.
The environment is altered as a result of replacing land cover with roads,
housing, and commercial and industrial structures.
"Human survival depends on the ability of the landscape to produce food,"
said Imhoff. "Food production can be fundamentally linked to primary
production or photosynthesis. If the capacity of the landscape to carryout
photosynthesis is substantially reduced -- then the ability of the planet
to support human life must also be diminished."
Imhoff said data from the mid-1990's from two different satellite systems
were combined with land cover maps and census information on population
and housing to study the effect of urbanization on photosynthetic production
in the United States. Nighttime images from a Department of Defense
satellite, which show a dramatic picture of Earth's city lights, were used
to determine which areas and how much land have been converted to urban,
suburban, or industrial use. Maps showing urban, peri-urban (suburban), and
non-urbanized areas were created from the "city-lights" satellite data.
"Using a computer, we combined the city-lights satellite data with
another type of satellite data that records a measure of 'greenness' or
photosynthetic potential of the landscape over the course of an entire
year," Imhoff said. "By merging the satellite data we could examine how
urbanization affects the potential of the land surface to carryout
photosynthesis by looking at the 'greenness' index inside and outside the
urbanized areas for the whole continental United States."
Results show that urbanization can have a measurable but variable impact
on photosynthetic productivity. Annual photosynthetic productivity can be
reduced by as much as 20 days in areas where housing and commercial land
use is very dense.
"However, we also found that in resource limited regions, human activity
can increase productivity by altering the environment," he said. "For
example, this was the case for arid and semi-arid areas where lawn
irrigation and planting changed the ecosystems from shrub lands and
desert to deciduous forests."
A most interesting finding according to Imhoff was that urbanization seems
to elongate the growing season, yet still reduces the overall productivity
of the land. "Vegetation greens up earlier in the spring and takes longer to
senesce in the fall, but has lower peak season productivity than similar
nearby areas that are not urbanized," he said. "This could be demonstrating
a profound urban heat island effect and have implications in climate change,
especially in the northern Hemisphere where urban development is most
intense."
Analysis of the data also found clear evidence that human beings definitely
tend to locate themselves on the most productive land and that those lands
are being transformed into less productive types.
"The results of this study should increase our awareness of the importance
of land use planning especially in the context of sustainable growth and
development," Imhoff stated. "Human survival depends on photosynthesis.
If urbanization and industrialization continue, the capacity of the
landscape to carry out photosynthesis is substantially reduced. "
For supporting images: http://svs.gsfc.nasa.gov/imagewall/AAAS
*****
Steve Roy
Media Relations Department
Marshall Space Flight Center
Huntsville, AL
(256) 544-0034
stev...@msfc.nasa.gov
http://www.msfc.nasa.gov/news
For Release: Feb. 17, 2000
RELEASE: 00-033
High in the Sky, NASA 'Heat Hunters' Combat Urban Phenomenon
NASA technology developed for use in the cold reaches of space is helping
researchers fight back against sweltering urban heat here on Earth.
Dr. Dale Quattrochi and Dr. Jeff Luvall are "heat hunters" for the Global
Hydrology and Climate Center, managed by NASA's Marshall Space Flight
Center in Huntsville, Ala. For more than three years, they've worked with
other NASA centers and the Environmental Protection Agency, as well as
state and local governments and city planners across the country, to
determine ways to make our cities more habitable. Their goal: to create
healthy, sustainable environments for current residents and future
generations.
On Monday, Feb. 21, Quattrochi will take part in a press briefing at the
annual meeting of the American Association for the Advancement of
Science, convening today at the Marriott Wardman hotel in Washington,
D.C. On Tuesday, he will present a paper on NASA's urban heat research
during a conference session titled: "Heat, Smog and Weird Weather:
Studying the Effects of Urban Sprawl From Space."
Cities often are dominated by asphalt and concrete and contain little
natural vegetation to shade buildings, block solar radiation and cool the
air. Thus, urban centers get much hotter during the day than rural areas.
That heat is stored and released at night, creating hot-air "domes" that
can keep temperatures in affected cities up to 10 degrees F warmer at
night than in suburbs or neighboring woodlands.
The effects are dramatic. Big cities suffer a marked upswing in ozone
formation -- a major pollutant and health threat to human beings. On
sweltering summer days, city power supplies are often taxed by
increased air conditioning use, as citizens struggle to beat the heat.
And those domes of trapped, heated air can actually create their own
weather patterns over urban areas, increasing rainstorms.
Equipped with remote sensing technology developed for the space program,
the heat hunters fly NASA aircraft over urban areas, documenting patterns
of heat formation in large metropolitan centers. This information helps
determine strategies to reduce heat islands, such as installation of
reflective roofing and paving materials to bounce thermal energy back
into the atmosphere.
To date, the heat hunters have conducted studies in Atlanta, Ga.;
Sacramento, Calif.; Salt Lake City, Utah; and Baton Rouge, La. Further
tests in other metropolitan areas are planned.
"There has to be a change in the mindset -- a new awareness about the
environment of our cities," Quattrochi says. "Education is the key."
More about the Global Hydrology and Climate Center
The Global Hydrology and Climate Center is a joint venture between
government and academia to study the global water cycle and its effect
on Earth's climate. Jointly funded by NASA and its academic partners, and
jointly operated by NASA's Marshall Space Flight Center in Huntsville, Ala.,
and the University of Alabama in Huntsville, the Center conducts research
in a number of critical areas. Satellite tracking of hurricanes promises to
improve global severe-weather forecasting capabilities; research into
lightning activity is providing new insight on the formation of tornadoes;
and NASA remote sensing technologies explore new ways to improve the
health of our cities, aid farm productivity and identify outbreaks of
disease.
More About the Marshall Center
NASA's Marshall Space Flight Center in Huntsville, Ala., is NASA's premier
organization for development of space transportation and propulsion
systems, NASA's leader in microgravity research -- unique scientific
studies conducted in the near-weightlessness of space -- and NASA's
leader for advanced large optics manufacturing technology.
In the past, Marshall played key roles in the development and operation
of the Saturn V rocket, Skylab, the Lunar Roving Vehicle, Spacelab and
the Hubble Space Telescope. Today, the Center's primary management
responsibilities include Space Shuttle propulsion systems; the Chandra
X-ray Observatory, future large-scale space optics systems; the X-33
and X-34 rocket planes and X-37 space plane; and all science operations
aboard the International Space Station.
Marshall also is responsible for developing advanced space transportation
systems designed to further humankind's exploration of space while
slashing the cost of getting there from today's $10,000 per pound to
only hundreds of dollars per pound, or even less. The Center is working to
bring a future among the stars closer to reality for the people of Earth.
Note to Editors / News Directors: To arrange post-conference interviews
with Dr. Quattrochi and Dr. Luvall, or to obtain photos supporting this
release, media representatives may contact Steve Roy of the Marshall
Media Relations Department at (256) 544-0034. For an electronic version
of this release, digital images or more information, visit Marshall's News
Center on the Web at:
[NOTE: A movie supporting this release is available at
http://www1.msfc.nasa.gov/NEWSROOM/news/video/2000/video00-033.htm]
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Andrew Yee
ay...@nova.astro.utoronto.ca