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Impact
of Human Development
The
Holocene has another unique characteristic as well. It is during this
time that humans become an important factor in the processes of Earth
history. Human development has already left a lasting imprint on the
geologic record, and it will likely continue to do so for some time.
To describe these effects, geologists use terms such as “anthropogenic
sediment” and “anthropogenic geomorphology.” Examples
include changes in sediment deposition from dam-building and river
diversion, leveling of topographic highs and infilling of lows, as
well as attempted stabilization of variable features such as barrier
islands.
The archeological record also attests to human adaptations to a changing
climate during the Holocene. Viking settlements in Iceland, Greenland,
and Newfoundland occurred during a warm, wet phase in Scandinavia
recorded around AD 900-1000. During this same time interval, however,
Mayan settlements in the tropical regions of Yucatán and Guatemala
were being abandoned because of unfavorable climatic conditions. In
Italy, Greece, and Spain the warming trend during Roman times initiated
higher rates of sediment accumulation in many rivers, which resulted
in the burial of Roman settlements under meters of silt. Fossils and
archeological remains on islands such as New Zealand, Madagascar,
Easter Island, and the Hawaiian Islands document the sudden extinction
of many animal species along with profound changes in vegetation that
followed the invasion of these islands by humans.
Most of these processes continue today, often at an accelerated pace.
As humans increasingly travel between continents, formerly isolated
animals and plants have opportunities to come into contact with one
another. Often the results are devastating, particularly for island
organisms that have few predator defenses. Anthropogenic changes in
Earth's atmosphere are ongoing, with most of the impact yet to be
felt. |
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Overview |
Climate Change and Variability |
Impact of Human Development
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