Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cities Built on Fertile Lands Affect Climate

11.02.2004


While cities provide vital habitat for human beings to thrive, it appears U.S. cities have been built on the most fertile soils, lessening contributions of these lands to Earth’s food web and human agriculture, according to a study by NASA researchers and others.


Comparing Post-Urban U.S. to Pre-Urban U.S., Difference in Total Annual Net Primary Production

This graphic compares modern U.S. annual Net Primary Production (NPP) to a computer-derived estimate of what the annual NPP would be in the absence of urbanization. The graphic shows areas with reductions or gains in NPP as a result of urban development. NPP measures plant growth by describing the rate at which plants use carbon from the atmosphere to build new organic matter through photosynthesis. Units are in grams of carbon per meter squared. Credit: Marc Imhoff/NASA


U.S. Urbanization and Net Primary Production

a) The top map depicts urbanized areas across the continental U.S. The map was generated from nighttime satellite images from the Defense Meteorological Satellite’s Operational Linescan System (DMSP/OLS) collected from October 1994 to March 1995. Red indicates urban areas; yellow marks those smaller towns, and suburbs on the peripheries of cities, or peri-urban areas; and black represents non-urban or rural areas. b) The lower map shows simulated total annual NPP for the U.S. at 1x 1km horizontal resolution. Units for NPP are in grams of carbon per square meter. Credit: Marc Imhoff/NASA



Though cities account for just 3 percent of continental U.S. land area, the food and fiber that could be grown there rivals current production on all U.S. agricultural lands, which cover 29 percent of the country. Marc Imhoff, NASA researcher and lead author of a current paper, and co-author Lahouari Bounoua, of NASA and University of Maryland, College Park, added that throughout history humans have settled in areas with the best lands for growing food.

"Urbanization follows agriculture -- it’s a natural and important human process," said Imhoff.Throughout history, highly productive agricultural land brought food, wealth and trade to an area, all of which fostered settlements.


"Urbanization is not a bad thing. It’s a very useful way for societies to get together and share resources," said Bounoua. "But it would be better if it were planned in conjunction with other environmental factors." Studies like this one, which appears in the current issue of Remote Sensing of Environment, may lead to smarter urban-growth strategies in the future.

The researchers used two satellites offering a combination of daytime and nighttime Earth observation data and a biophysical computer model to derive estimates of annual Net Primary Productivity (NPP). NPP measures plant growth by describing the rate at which plants use carbon from the atmosphere to build new organic matter through photosynthesis. NPP fuels Earth’s complex food web and quantifies amounts of carbon dioxide, a greenhouse gas, which plants remove from the atmosphere.

Nighttime-lights data from the Defense Meteorological Satellite Program and a vegetation-classification map created at NASA’s Goddard Institute of Space Studies, New York, were used to portray urban, peripheral and non-urban areas across the United States. In this way, the researchers calculated the extent and locations of U.S. urban and agricultural land.

In addition, observations from the Advanced Very High Resolution Radiometer instrument, aboard the National Oceanic and Atmospheric Administration’s polar orbiting satellites, were used to calculate the Normalized Difference Vegetation Index. This index is a measure of plant health, based on the principle that plants absorb solar radiation in the red part of the spectrum of sunlight used for photosynthesis during plant growth. These data were then entered into a Stanford University computer model to derive NPP.

The computer model created a potential pre-urban American landscape, which was used to compare and estimate the reduction of NPP due to current urban-land transformation.

For the continental United States, when compared to the pre- urban landscape, modern cities account for a 1.6 percent annual decline in NPP. This loss offsets the gain in NPP of 1.8 percent annually from increased farmlands. The result is striking, given the small area that cities cover, relative to agricultural areas.

A reduction of this magnitude has vastly unknown consequences for biological diversity, but it translates to less available energy for the species that make up Earth’s complex food web. The loss of highly fertile lands for farming also puts pressure on other means to meet the food and fiber needs of an increasing population. On the local scale, urbanization can increase NPP, but only where natural resources are limited. It brings water to arid areas, and "urban heat islands" extend the growing season around the urban fringe in cold regions. These benefits, however, do not offset the overall negative impact of urbanization on NPP.

NASA scientists developed the city lights map, and the U.S. Geological Survey used a technique to create the Normalized Difference Vegetation Index data. Research partners include the University of Maryland’s Earth System Science Interdisciplinary Center, the World Wildlife Fund, and the Center for Conservation Biology at Stanford University.

Krishna Ramanujan | GSFC
Further information:
http://www.gsfc.nasa.gov/topstory/2004/0202cityland.html

More articles from Agricultural and Forestry Science:

nachricht Filling intercropping info gap
16.11.2017 | American Society of Agronomy

nachricht Climate change, population growth may lead to open ocean aquaculture
05.10.2017 | Oregon State University

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

NASA detects solar flare pulses at Sun and Earth

17.11.2017 | Physics and Astronomy

NIST scientists discover how to switch liver cancer cell growth from 2-D to 3-D structures

17.11.2017 | Health and Medicine

The importance of biodiversity in forests could increase due to climate change

17.11.2017 | Studies and Analyses

VideoLinks
B2B-VideoLinks
More VideoLinks >>>