Evaluating the effects of natural climate variability and human impact on landscapes is important because it affects plant and animal distributions worldwide. The scientific interpretation of
these long-term dynamics of vegetation change is particularly relevant in the late Quaternary period(circa 150,000 yr.) which encompassed several glacial-interglacial cycles. Measuring the direction, magnitude, and rates of these shifts can help
scientists understand present plant and animal distributions, as well as anticipate how these distributions might change in the future.
Vegetation shifts and climatic changes which occurred prior to human observation can be reconstructed by
utilizing a variety of paleoclimatic proxies (tree rings, fossil pollen, ice and coral cores, lake and ocean sediments). Unfortunately, none of these proxy indicators are present in sufficient quantities in the North American deserts to allow
vegetation cover and climate reconstructions of these regions.
Desert Laboratory, U.S. Geological Survey, Tucson, AZ
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