Environmental Engineering Reference
In-Depth Information
megafauna that survived into the Holocene, became more numerous before and
during the human colonization of the region and before the extinction of mammoths
and horses. There are no signs of any overkill or blitzkrieg but clear links between
climate change and extinctions and human colonization: indeed, “the humans might
have been not so much riding down the demise of the Pleistocene mammoth steppe
as they were being carried into AK-YT on a unique tide of resource abundance”
that was created by the Pleistocene-Holocene transition (Guthrie 2006, 209).
New research tends to view late Pleistocene extinctions as a result of multiple
causes, including both natural (above all climate and vegetation change) and anthro-
pogenic (mainly selective hunting and i re) factors (Yule 2009). For example, in their
state-of-the-debate review, Koch and Barnosky (2006) move away from explaining
the extinctions simply on the basis of a sweeping wave of hunting that began imme-
diately after human colonization. They conclude that the anthropogenic extinction
was a combination of direct effects (hunting) and indirect impacts (competition for
resources, habitat alteration), and that the outcome could have been less severe in
the absence of concurrent climate change in many affected regions.
The latest two analyses of megafaunal disappearance also concluded that the
observed pattern of extinction was not due to a single factor but to the combination
of climate change and human action. Lorenzen et al. (2011) used ancient DNA,
models of species distribution and the human fossil record to show that individual
species responded differently to climatic shifts, habitat changes, and human encroach-
ment: climate change alone can explain the demise of Eurasian musk ox and woolly
rhinoceros, while the combination of changing climate and intensii ed hunting was
behind other extinctions. Prescott et al. (2012) modeled the process of extinction
on i ve continental landmasses and concluded that the outcome is best explained by
combining human arrival and climatic variables.
Unfortunately, these new, nuanced interpretations stressing continental specii cs
and avoiding single-factor attributions make it even more difi cult to estimate the
extent to which hunting affected the late Pleistocene zoomass disappearance. Even
the simplest models of extinction due to overkill hinge on concatenated assumptions
based on inadequate knowledge. For the estimates of densities and territorial extent
of megafaunal species we have to rely on a combination of sparse archaeological
records, general metabolic expectations, and analogs with modern large-sized
animals. And much less is known about actual hunting preferences (which species
were deliberately targeted, which ones were killed in opportunistic manner), about
the specii c composition of regional or continental kills, and about the rates of
hunting success.
