Global vegetation plays a key role in sustaining life on Earth. We have just begun to understand how the thin film of living matter on Earth is sustained by global-scale biogeochemical cycles. Closely related to the biogeochemical cycles are changes in the populations of life forms within the ecosystems of the world, both in numbers of species and in the abundance of individuals within the species.
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Although changes in populations of life forms are not new, it is apparent that they are now occurring at an accelerated rate, and that human beings, comparatively recent agents of global modification, are likely the cause of most of this accelerated change. In order to maintain the conditions desirable for human habitation it is important that we understand the role of natural biological diversity in maintaining the global balance of the environment and the extent to which the world's ecosystems are being affected by human activities.
The images above are as follows:
GLOBAL BIOPHYSICS
NOAA Advanced Very High Resolution Radiometer (AVHRR) data processed into normalized difference vegetation index (NDVI) for August 1987. Dark-blue areas represent dense vegetation, pale blues and greens represent light vegetation, and pink and dark-red areas represent sparse vegetation.
LEAF AREA INDEX
The NDVI data have been analyzed to calculate global monthly fields of green leaf area index (square meters of green leaves per square meter of surface). Green represents dense vegetation, while brown indicates desert.
VEGETATION TYPE
Seasonal variations in the NDVI as observed by NOAA AVHRR can be analyzed to establish a global vegetation classification. The major biomes are shown in this analysis: tropical forests, deserts, agriculture, northern forests, etc. Purple and green areas represent dense vegetation, tan areas represent sparse vegetation.
