Global changes in climate forced major changes in plant and animal distributions, especially in the high and mid-latitudes. During the Full Glacial, remains of trees that now grow in the northern boreal forest were found in Tennessee where their fossils were associated with deciduous hardwoods and even cypress-swamp types, creating strange mixtures of genera. Plants and animals that had dispersed to lower latitudes and in areas of southerly environments during glacials dispersed northward again during the postglacial warming. Thus, the Quaternary period records some of the more extreme climate changes known in Earth's history.

SEE ALSO: Ice Ages; Little Ice Age; Milankovitch, Milu-tin; Orbital Parameters, Eccentricity; Orbital Parameters, Obliquity; Orbital Parameters, Precession.

BIBLIOGRAPHY. H.R. Delcourt and P.A. Delcourt, Quaternary Ecology: A Paleoecological Perspective (Chapman & Hall, 1998); Alan Graham, Late Cretaceous and Cenozoic History of North American Vegetation (Oxford University Press, 1999); P.D. Moore, W.G. Chaloner, and P. Scott, Global Environmental Change (Blackwell Science, 1996).

Estella B. Leopold University of Washington

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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