Geography Reference
In-Depth Information
There has never been any question that, at least under certain conditions, both species
can achieve very high densities (pikas more so than zokors), and have locally dramatic
impacts on vegetation. More critically, there has also never been any question that both
species are associated with grasslands characterized by sparse ground cover and low-
growing plants (see Figures 7.5 and 7.6). In short, both species appear most common in
areas commonly (if uncritically) referred to as “degraded.” But mere association begs
the question: do pikas and zokors
cause
these grassland conditions, or is the presence of
pikas and zokors (at least in high densities) the
result
of such grassland conditions? From
simple observations, either situation could be the case, but the implications for wildlife
management—the all-important balancing between human needs and biodiversity protec-
tion—could hardly be more disparate. If these species cause grassland degradation, their
presence constitutes a genuine conflict with economic use of grasslands by pastoralists,
and their reduction, or even elimination where livestock production is a high priority, is
a rational response. Conversely, it could be that these species—for whatever reason—do
better (i.e., have higher survival and fecundity) in habitats that already—for whatever
reason—have these “degraded” characteristics. If so, we should view their presence as
a useful warning that something else is awry, and rather than strive for their elimination
or reduction, address the underlying problem.
As might be expected, lacking resolution to this conundrum, early government policy
following 1949 landed squarely on the first possibility, asserting that these two species
Figure 7.5
Pika burrow density as a function of vegetation cover.
70
60
50
40
30
20
10
0
60
70
80
90
100
Vegetation Cover (%)
Source:
Adapted from Fan et al. 1999.
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