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Plateau Geology
Plateaus can develop from numerous geological activities, plates converging and pushing, domes risings from pressure underneath or from volcanic activity which creates increasingly thick layers. They are relatively flat regions sometimes consisting of many plateaus strung together. The altitude of expansive plateaus varies. The Tibetan Plateau, the world's most expansive and highest, is over 12,000 feet above sea level in some regions. It also covers over 2.4 million square kilometers of land. Plateaus often have deep chasms where rivers have cut their way through the elevated terrain over time. The Grand Canyon on the Colorado Plateau is an example of a plateau canyon. Plateaus often have unusual rock formations cut by winds that rake across the land.
Plateau Ecosystems
Because of the vast differences in plateau altitude, geology and abiotic factors such as wind and rain, there is no one ecosystem that can actually be labeled a "plateau" ecosystem. Large plateaus often contain several biotic communities which form because of varying regional aspects of the plateau. A plateau covering large areas of land may vary greatly in altitude, climate and rainfall from region to region. Biotic communities that form in each region are determined by their tolerance to localized abiotic features of that region, just as they do elsewhere on the globe. The more uniform the geology of the plateau, therefore, the more uniform the ecosystem of the plateau will be.
Biotic Communities
Biotic communities differ from region to region on extensive plateaus. On the Colorado Plateau, biotic communities include several types of forests, alpine tundra, mountain and arid grasslands, mountain wetlands, chaparral/scrub and riparian areas. The Tibetan Plateau contains alpine and subalpine meadows, alpine and subalpine conifer forests as well as desert and semidesert areas. Inaccessibility or hostile climates have maintained biological diversity of some plateau regions, such as the Nujiang Langcang Gorge, which has deep gorges and steep ridges, and the frigid, dry Central Tibetan Plateau alpine steppe. Many regions of plateaus are not inaccessible, and human activities along with climate change are causing rapid changes in plateau biodiversity.
Changes In Biotic Communities
Scientists are just beginning to understand plateau ecosystems. Much of the Tibetan Plateau is so little understood that scientists still don't know which species inhabit some regions. Unfortunately, human activity has already diminished much biodiversity and is continuing to cause rapid changes on plateaus. For example, beavers were hunted out and no longer exist on the Colorado Plateau. Scientists now know that beavers were important in waterway maintenance and fish habitat. Agriculture, livestock grazing and fire control are causing a change of vegetation on grasslands, where trees and woody shrubs are invading areas where grass cover is diminished on plateaus. As scientists learn how biotic communities function on plateaus, they are taking action to stop human damage and slow changes occurring in these high regions.