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 Earths 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 Satellites 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 -- its 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.
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