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Our land is changing. Forest is changing to farmland, farmland is changing to suburbs; cities are growing. Shorelines are shifting; glaciers are melting; and ecosystem boundaries are moving.
Land cover change has effects and consequences at all geographic scales: local, regional, and global. Human changes to the land are enabling our own populations to grow, but they also are affecting the capacity of ecosystems to produce food, maintain fresh water and forests, regulate climate and air quality, and provide other essential functions necessary for life. It is critical for us to understand the changes we are bringing about to the Earth system, and to understand the effects and consequences of those changes for life on our planet. The first step in understanding change is monitoring, and the second step is analysis. Landsat satellites have been observing the Earth's land surface since 1972, providing us with an invaluable record of landscape scale change. |
The Aral Sea |
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The Aral Sea lies between Uzbekistan (to the south) and Kazakhstan (to the north). Once the fourth largest lake in the world, and now less than half of its original size, the Aral Sea is a terminal, or endorheic, sea (meaning no water flows out of it). It is fed by the Syr Darya and the Amu Darya Rivers, but Soviet river diversions for irrigation made over 40 years ago have starved the Aral Sea of water.
These images are from 2000 and 2009. Caption by Laura Rocchio. |
Bolivian Deforestation |
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These images show the progression of deforestation in Bolivia from 1984 to 2000. This area lies east of Santa Cruz de la Sierra, Bolivia, in an area of tropical dry forest.
Since the mid-1980s, the resettlement of people from the Altiplano (the Andean high plains) and a large agricultural development effort (the Tierras Baja project) has lead to this area's deforestation. Caption from USGS. |
Cairo, Egypt |
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A city with a 5,000-year history, Cairo, Egypt, sits on the Nile River about a hundred miles south of the Mediterranean Sea. In 2006, the Cairo urban area had a population of over 17 million and covered an area of 6,600 square kilometers (82.6 square miles). In 1975, there were only 6 million there.
The city appears as a large dark brown and purple mass in the center of the image. The bright green regions surrounding the city are farms along the fertile banks of the Nile, which have provided sustenance for residents of the region since before recorded history. Just outside this green swath is the arid and forbidding Sahara Desert. Caption from Earth Observatory |
Hobet Mine, Boone County, West Virginia |
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In West Virginia’s Appalachian Mountains, multiple layers of coal lie underground in ancient rocks. In some places, miners remove mountaintops to get at that coal. Acquired by NASA’s Landsat 5 satellite, these natural-color images show the growth of one such mine, Hobet, between 2000 and 2010.
NASA Earth Observatory image created by Robert Simmon, using Landsat data provided by the United States Geological Survey. Caption by Michon Scott. |
New Orleans, Louisiana – the Effects of Hurricane Katrina |
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In late August 2005, Hurricane Katrina left much of New Orleans inundated with flood water. New Orleans sits between Lake Pontchartrain and the Mississippi River. The city appears a pinkish shade in the April 2000 image. In the post-Katrina image acquired on Aug. 30, 2005, the flooded portions of the city appear a dark blue color.
Caption by Laura Rocchio. |
Las Vegas, Nevada |
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In the 25 years that Landsat 5 has been in orbit, the desert city of Las Vegas has gone through a massive growth spurt. The outward expansion of the city is shown here with false-color images. The dark purple grid of city streets and the green of irrigated vegetation grow out in every direction into the surrounding desert. These images were created using reflected light from the shortwave infrared, near-infrared, and green portions of the electromagnetic spectrum (Landsat 5 TM bands 7,4,2), from 1984 and 2009.
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Please give credit for this page to:
NASA/Goddard Space Flight Center |