From NASA - Cities Built On Fertile Lands Affect Climate

[Guest guest]

In a message dated 2/12/04 10:53:50 AM Eastern Standard Time,

Idol@... writes:

> 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.

>

> 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.

Did I miss something, or did they simply assume that higher plant health and

rate of growth is purely a function of higher soil fertility?

Increased CO2 increases plant growth, so why couldn't this simply be due to

an increased concentration of CO2 in cities?

Chris

[Guest guest]

Elvia H.

Headquarters, Washington February 11, 2004

(Phone: 202/358-1696)

Krishna Ramanujan

Goddard Space Flight Center, Greenbelt, Md.

(Phone: 607/273-2561)

RELEASE: 04-059

CITIES BUILT ON FERTILE LANDS AFFECT CLIMATE

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.

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 land, 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 land's Earth System Science Interdisciplinary

Center, the World Wildlife Fund, and the Center for

Conservation Biology at Stanford University.

For more information and images on the Internet, visit:

http://www.gsfc.nasa.gov/topstory/2004/0202cityland.html

For more information about NASA on the Internet, visit:

www.nasa.gov

-end-

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[Guest guest]

,

Unbelievable! Having ports for a lot of people to be near was more important

than agriculture? Honestly, were people so removed from their food supply

then that it was expected only someone or somewhere else could provide food?

In my town there's less than half a dozen small spots that are rich enough

to be considered farmland. Last year when I saw the planning map, had been

trying for 8 years to build up this land. Right beside us where the biggest

development in town is instead, is classified agricultural land.

> 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.

Wanita