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An ecosystem is a complex, self-regulating association of living plants and animals and their nonliving physical environment.
Source of image: Forest Ecosystem Dynamics (FED) Project
Changes in the patterns of land use and the monitoring of ecosystem has largely been accomplished on a global scale by analyzing data from the LANDSAT satellites. With the launch of the Landsat 1 in 1972, the Landsat program is the longest-running program of remote-sensing from space. It images the entire earth once in 16 days.
The Landsat satellite carries a multispectral scanner (MSS) and starting with Landsat-4 in 1982, also a Thematic Mapper (TM). MSS and TM are instruments that measure electromagnetic radiation from the sun reflecting off the Earth. MSS data has a spatial resolution of about 80 m x 80 m, and measures the intensity of reflected light in four bands: green light, red light and two different wavelength bands of infrared. TM has more bands and a 30 m x 30 m resolution.
Source of image: NASA Pathfinder
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The MSS and TM bands were selected to maximize their capabilities for detecting and monitoring different types of Earth resources. For example, MSS band 1 can detect the visible green reflectance of vegetation, and band 2 of MSS is designed for detecting chlorophyll absorption in vegetation. MSS bands 3 and 4 are ideal for near-IR reflectance peaks in healthy green vegetation and for detecting water-land interfaces. Plants have evolved to absorb light for photosynthesis, but reflect IR that would just heat them up and waste all their moisture trying to remain cool (like a person staying in the shade to avoid sweating and dehydration).
Three basic components of visible light are red, green and blue light (RGB). Any color in the visible spectrum can be made by adding these three (the "primary additive colors") together in some proportion. This is how a computer monitor works (you may have heard of "RGB" monitors).
Source: EROS
The Landsat images are commonly color composites, made by assigning the three primary colors to three bands of the MSS sensor. Green fields won't necessarily look green in an image. These are not photographs. Typically things that reflect red light are displayed as green, things that reflect green light are displayed as blue, and health vegetation which reflects large amounts of infrared are displayed in red.
The standard band combination makes vegetation appear as shades of red-- brighter reds indicating more vigorously growing vegetation. Soils with no vegetation or sparse vegetation range from white (for sand) to greens or browns, depending on moisture and organic matter content. Water appears blue. Deep, clear water is dark blue to black, while sediment-laden or shallow waters will appear lighter. Urban areas appear blue-gray. Clouds and snow are both bright white-- they are usually distinguishable from each other by the clouds' shadows.
The tropical rainforest covers less than 10% of the global land surface, contain 50% of all known species, and about two-thirds of the global plant biomass. Most of South American tropical rain lies in the Amazon drainage basin within Brazil. Monitoring the rainforest destruction done by counting the number of fires seen on weather satellite images, and by comparing Landsat images of the region over different years.
Systematic cutting of the forest vegetation starts along roads.
"Trans-Amazon Highway being cut through the rainforest near Altamira, Brazil -- one example of the deforestation that takes place along with traditional frontier expansion. Photo courtesy of Nigel J. H. Smith"
These images show a portion of the state of Rondônia, Brazil, in which tropical deforestation has occurred. The 1975 and 1986 images are MSS data. The 1992 image is TM data. Approximately 30% (3,562,800 sq km) of the world's tropical forests are in Brazil. The estimated average deforestation rate from 1978 to 1988 was 15,000 sq km per year. Systematic cutting of the forest vegetation starts along roads and then fans out to create the "feather" or "fishbone" pattern shown in the eastern half of the 1986 image. The deforested land and urban areas appear in light blue; healthy vegetation appears red.
1975
1986
1992
A recent NASA study showed that deforestation of the Amazon will cause local climate changes including: 1) less rainfall, 2) increased surface winds, 3) change in precipitation patterns around deforested region, and 4) increased flooding.
Do Exercise 2
Source: EROS Earthshots
"Look at the 1972 and 1988 images. Compare them to the map. Much of the natural shortgrass prairie of western Kansas is now irrigated cropland. The predominant crop in this area is corn. Light-colored cultivated fields in the images are fallow or recently harvested wheat fields."
"These images show that center-pivot irrigation systems (red circles) have increased in number since the early 1970s. Irrigation in this area is from the Ogallala Aquifer, which underlies an area from Wyoming to Texas. Images such as these play a major role in measuring irrigated crop acreage, a key component of modeling aquifer response to changes in water use."
1972
1988
1972
1988
Do Exercise 3
The problem of wind erosion affects about 30 million hectares of land in the United States. Wind erosion physically removes the most fertile portion of the soil. Soil removed by the wind becomes suspended in the atmosphere as dust. Dust becomes the air pollutant called particulate matter. It obscures visibility and causes a series of health related risks and damages.
During the 1930's, a prolonged dry spell culminated in dust storms and soil destruction of disastrous proportions. The "black blizzards" of the resulting Dust Bowl inflicted great hardships on the people and the land.
Source: www.discovery.com
Do Exercise 4
Learn more about the Dust Bowl. at Discovery Online or at the Smithsonian
Visit the Wind Erosion Research Unit at Kansas State University
According to the International Programs Center, U.S. Bureau of the Census, the total population of the World, projected to 12/2/97 at 9:18:50 AM EST is
5,880,244,396.
Smithsonian Institutions's Conservation and Research Center
NASA's Forest Ecosystem Dynamics program
NASA's Boreal Ecosystem-Atmosphere Study
NASA Landsat Pathfinder Humid Tropical Forest Inventory Project
USGS Earth Resources Observation Systems (EROS)
FIFE (First ISLSCP Field Experiment) Project