Earth’s surface. By carefully measuring the wavelengths and intensity of visible
and near-infrared light reflected by the land surface back up into space, scientists
use the “Vegetation Index” (NDVI) to quantify the concentrations of green leaf
vegetation around the globe [82]. Then by combining the daily Vegetation Indices
into 8-, 16-, or 30-day composites, scientists create detailed maps of the Earth’s
green vegetation density that identify where plants are thriving and where they are
under stress (i.e., due to lack of water). To obtain the NDVI values for vegetation
biomass or stress studies in smaller areas, higher resolution satellite systems, such
as Landsat TM or SPOT, are being used [69].
6 Detecting and Mapping Wetlands
Freshwater wetlands include bottomland hardwoods, riparian forests, bogs, vernal
pools, and emergent marshes.
Freshwater wetlands greatly influence water quality, increase detention times of
floodwaters, provide habitat for wildlife, serve as spawning and nursery grounds for
fish, and contribute to the aquatic food chain [85, 86]. Wetlands also provide flood
protection, protection from storm and wave damage, water quality improvement
through filtering of agricultural and industrial waste, and recharge of aquifers
Fig. 5 This image shows the Normalized Difference Vegetation Index (NDVI) anomaly of the
Horn of Africa for August 1984. The NDVI anomaly indicates the vigor of vegetation relative to
the long-term average. Dark red/brown indicates the most severe drought, light yellow areas are
normal, and green areas have denser than normal vegetation. Courtesy: NOAA National Weather
Service
48
V. Klemas and A. Pieterse
and near-infrared light reflected by the land surface back up into space, scientists
use the “Vegetation Index” (NDVI) to quantify the concentrations of green leaf
vegetation around the globe [82]. Then by combining the daily Vegetation Indices
into 8-, 16-, or 30-day composites, scientists create detailed maps of the Earth’s
green vegetation density that identify where plants are thriving and where they are
under stress (i.e., due to lack of water). To obtain the NDVI values for vegetation
biomass or stress studies in smaller areas, higher resolution satellite systems, such
as Landsat TM or SPOT, are being used [69].
6 Detecting and Mapping Wetlands
Freshwater wetlands include bottomland hardwoods, riparian forests, bogs, vernal
pools, and emergent marshes.
Freshwater wetlands greatly influence water quality, increase detention times of
floodwaters, provide habitat for wildlife, serve as spawning and nursery grounds for
fish, and contribute to the aquatic food chain [85, 86]. Wetlands also provide flood
protection, protection from storm and wave damage, water quality improvement
through filtering of agricultural and industrial waste, and recharge of aquifers
Fig. 5 This image shows the Normalized Difference Vegetation Index (NDVI) anomaly of the
Horn of Africa for August 1984. The NDVI anomaly indicates the vigor of vegetation relative to
the long-term average. Dark red/brown indicates the most severe drought, light yellow areas are
normal, and green areas have denser than normal vegetation. Courtesy: NOAA National Weather
Service
48
V. Klemas and A. Pieterse