Geoscience Reference
In-Depth Information
the means by which the early Holocene climate change dramatically shit ed
the vegetation from a dense forest regime to a more open forest dominated
by oak trees.
humans and fire
Although i res and climate largely controlled vegetation shit s during the
Holocene, some archaeologists argue that early humans may have also played
an important role in shaping the types of plant communities in some parts
of the West. h ese researchers suggest that native populations managed the
land over the millennia with controlled burning, pruning, weeding, irrigation,
and tillage. In other words, the early humans were not merely passive hunter-
gatherers who collected their food from a wild landscape, as was once thought.
According to Kent Lightfoot and Otis Parrish at the University of
California, Berkeley, hunter-gatherer populations may have used controlled
burning to clear underbrush and areas of dead timber, eradicate pests and
diseased plants, and recycle nutrients back into the soil. Fires may also have
been used to clear water holes of vegetation, drive wildlife into traps during
group hunting, and mark territories or claim resources. h e geographic extent
and intensity of these controlled burns over time is a subject of Lightfoot's
current research, and, in his work with Parrish, he has hypothesized that
some of the landscape patterns we see over the past 13,500 years or so at er
humans arrived in the West were related to intentionally set i res, not just
those ignited naturally by lightning strikes.
early holocene climate cycles
Broad cycles of climate change during the Holocene have been apparent from
the early part of the epoch. h e evidence is found both on land and in the
oceans. h e bristlecone tree line migrated downslope as climate cooled and
upslope again as climate warmed, approximately every 2,500 years. h ese
broad cycles in temperature are also apparent in the waxing and waning of
mountain glaciers.
Of the West Coast in the Pacii c, there is also evidence that seawater
temperatures shit ed with similar broad cycles—temperature shit s that
af ected the assemblages and oxygen isotopic compositions of coastal
