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Photographic analyses
of land use practices give insight into changes. Linear functions can be used to project
the rate of future change. As growing human population requires an ever-increasing share
of the Earth's surface on which to live, human activities change the distribution of
plants and animals, alter drainage patterns, and modify natural boundaries. In doing so,
mankind changes either the reflective or emissive properties of the surface. Such changes
are detectable from space. Human actions that change the reflectance or color of the
Earth's surface can be recorded with space photography. Activities include: |
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On the Way
to the Moon, Man Discovered the Earth
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Earthrise from Apollo 8 |
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- DEFORESTATION
. Forests are optically dense, green areas. The cutting of the trees
produces a more reflective surface and exposes a different color. Deforestation scars are
seen in the rain forests throughout the world. Forests are often cleared by setting fire
to the vegetation, and smoke from these fires is visible from space.
- URBANIZATION
. Urban areas are delineated by highly reflective paved surfaces.
Because the growth of cities is at the expense of vegetated surfaces, the increase in
reflectivity can be measured.
- FLUVIAL SEDIMENT LOADS
. Clear cut forestry practices in many tropical countries have
altered the sedimentary load of the rivers that drain the forest. Rivers loaded with
sediment have a different color than "clean" rivers that drain forested areas.
Sediment laden rivers, such as the Betsiboka River of Madagascar, are now red-brown when
seen from space.
- DESERTIFICATION
. The reflective surface of deserts and eolian sediment patterns are
also visible from space. The encroachment of deserts over once vegetated surfaces will
register a shift in the optical and textural character.
- COASTAL EROSION
. Analysis of the position of the coastal features can be used to
determine the rate and location of large-scale coastal changes. Dramatic rates of erosion
can be seen on the edge of the Nile and Ganges river deltas.
- LAKE LEVELS
. Changes in boundary relations can detect variation in water levels in
lakes (e. g., Lake Chad) or inland seas (e.g., Aral Sea).
- WETLANDS
. The delineation of wetlands is sometimes difficult. Changes in vegetation
color and the sea land boundary are sometimes needed to detect loss.
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