The Greater Yellowstone Ecosystem - Mountains and Plains: The Ecology of Wyoming Landscapes - page 258

critics immediately challenged the natural regula-
tion approach to managing the Yellowstone elk . 49 they
contended that YnP did not contain the key winter hab-
itat necessary to sustain a self-regulating elk population.
in winters since time immemorial, they argued, the
Yellowstone elk had migrated out of the relatively high-
elevation YnP to reach snow-free grasslands at lower
elevations outside the current park boundary. Much of
this area was now private land, converted to agriculture,
roads, and other developments that impaired the qual-
ity of the habitat for elk . 50 Hunting pressure in these
areas also reduced elk numbers significantly in severe
winters, and forced many of the elk to remain in the
park during mild winters. critics argued that regulation
of the elk population could never be truly natural, and
that unnatural overuse of the vegetation inside the park
was unavoidable. to address this issue of elk migrating
out of the park during severe winters, wildlife agencies
and conservation groups eventually began to purchase,
or protect in other ways, some of the key elk wintering
areas along YnP's boundaries.
notably, the assumption that wintering elk were
irreparably damaging the vegetation of YnP's northern
range has not stood up to research findings. in 1998 the
U.S. congress directed the national Academy of Sciences
to review all available science related to the manage-
ment of ungulates and the effects of ungulates on the
vegetation of YnP's northern winter range, to clarify
what is known and what is not known. 51 A committee of
twelve eminent scholars concluded that the condition
of the northern range is indeed different today than
when europeans first arrived in the region, but that the
ecosystem is not in imminent danger of losing major
components or crossing any threshold that would lead
to irreversible changes. the committee determined that
grasslands on the northern winter range generally show
less dramatic impacts of ungulate use than do aspen for-
ests and willow communities . 52 Despite the consump-
tion of 45 percent of the forage biomass by elk, the plant
growth in grazed areas of YnP's northern winter range
was 36-85 percent higher than in exclosures, suggest-
ing compensatory growth 53 (see chapter 6).
one reason heavy grazing has had such minimal
adverse effects on the herbaceous vegetation of the win-
ter range is that most foraging occurs during fall and
winter, when the plants are dormant. in spring and
summer, elk and bison move to higher-elevation sum-

mer ranges, which are more extensive than their winter
ranges. these seasonal movements minimize grazing in
any particular area . 54 Park biologist Douglas Houston
concluded in 1982, after 10 years of research, that reduc-
tions in the size of the elk herd were not necessary . 55
in contrast to the grasslands, aspen and woody ripar-
ian plants have continued to be significantly affected
by herbivores. 56 Approximately 85 percent of tree-sized
aspen on the northern winter range became established
prior to 1920; these old trees are gradually dying and
generally are not being replaced by young aspen sprouts
and seedlings . 57 Willows and associated woody riparian
vegetation in many areas appear degraded, with low
stature, many dead branches, and new growth confined
to the base of the plant rather than the top; seedlings
of willow and cottonwood are often observed, but few
survive . 58 t he national Academy of Sciences committee
evaluated several alternative hypotheses to explain the
lack of widespread aspen and willow regeneration dur-
ing the twentieth century. the committee determined
that neither twentieth-century climate conditions nor
fire suppression were sufficient explanations in them-
selves for the paucity of recent aspen and willow regen-
eration and concluded that ungulate browsing was
the primary mechanism. 59 nevertheless, even though
browsing is suppressing aspen and willows, the panel
of scientists concluded that none of these species was in
imminent danger of extirpation on the winter range. 60
Following cessation of artificial regulation in 1968, the
northern Yellowstone elk population increased rapidly,
growing from fewer than 4,000 animals in 1968 to more
than 19,000 by 1988 (fig. 15.13). 61 the controversy over
elk management in YnP and elsewhere did not subside,
but the plot thickened. in 1988 the largest fires in more
than a century burned approximately a third of YnP,
including a large portion of the northern winter range
and surrounding lands. With ongoing climate change,
the habitat has changed because of drought, a widespread
epidemic of bark beetles, and the decline of whitebark
pine due to an exotic disease. And then, in 1995, the gray
wolf was reintroduced—a major predator of elk. the so-
called elk problem now became part of the broader chal-
lenge of managing fire, forests, and wildlife as a whole.

Fire Management

Systematic efforts to eliminate wildfires were initiated
in YnP with the arrival of the U.S. Army in 1886 , 62