Holocene Epoch (0.01 mya-present)
The Holocene begins immediately following the last major glacial epoch,
11,000 years ago. Ice core evidence suggests the epoch has endured only small-scale climate
shifts. One of these, known as the "Little Ice Age," begins about 650 years ago (A.D. 1350)
and lasts only about 550 years. Scientists think the relatively warm overall conditions
might be temporary -- an interglacial period between ice ages.
Modern humans evolve and spread over the planet well before the Holocene
began. Yet the influence humans have exerted on life and the environment in the short time
since the rise of the first civilizations -- only several thousand years -- has been unlike
that of any other organism.
Some estimates indicate that as many as 20 percent of all plant and
animal species present today will be extinct by the year 2025. More information is needed
to determine whether the current and expected levels of extinction are in line within
the natural background levels of species replacement, or whether these have been
accelerated by human practices such as hunting, pollution, flood control, and
deforestation.
|
