Environmental Engineering Reference
In-Depth Information
by low population numbers and low technical capacities. Foragers had a clearly
discernible but rarely a highly destructive inl uence. Harvesting to complete exter-
mination might seem to be an exceedingly difi cult if not impossible task to achieve
with organisms whose natural populations numbered in millions of individuals. As
I have tried to demonstrate, mammoth extinctions do not belong to that category:
hunting was clearly a factor, but hunting alone did not eliminate the species.
But that incredible feat of complete extinction was accomplished in the case of
an animal whose numbers were in the billions. Audubon, after years of witnessing
the extensive slaughter of passenger pigeons, thought them to be safe because they
commonly quadrupled their numbers every year, and always at least doubled it—
but they did not make into the twentieth century (Jackson and Jackson 2007). Many
less numerous species were eliminated by hunting since the beginning of the early
modern era. Near extinctions, in which the original overwhelming richness has been
reduced to tiny, isolated remnants, have been numerous, affecting species ranging
from the American bison (essentially gone by the 1890s) to the Newfoundland cod
(impossible to catch in large quantities by the 1980s).
And these near extinctions continue to unfold, with the gravest threats (despite
the continued tropical losses) not on land but in the ocean because of the combina-
tion of persistent overexploitation of all commercially valuable species and frenzied
competition to catch the most valuable specimens. Only the great whales have
become exempt from this global hunt, and Schneider and Pearce (2004) have shown
that the dismal economics of whale hunting, rather than the public opinion in most
Western nations, was the main reason for the 1986 moratorium: declining stock
and the resulting high unit catch costs, and higher incomes that lowered rather than
increased demand for whale products, were the decisive factors.
There is no shortage of analyses and reviews explaining the follies of modern
i sheries (none as irrational as the fact that the continuing overi shing has been
heavily subsidized by virtually all governments of maritime nations) and suggesting
steps toward ending the overexploitation, rebuilding endangered stocks, and making
a transition to truly sustainable catches (Hilborn et al. 2003; Worm et al. 2009;
M. D. Smith et al. 2010). But political pressures and narrow national interests have
made it very difi cult to translate these rational precepts into everyday actions.
Similarly, it would be naïve to expect that the expanding aquaculture will sufi ce to
prevent further deterioration of wild stocks; indeed, the culturing of carnivorous
species may only accelerate the overall decline.
The most worrisome hunting on land affects the two remarkable mammalian
families, anthropoid primates, which are killed for their meat, and elephants,
