NEPA--Environmental Assessment

intensity on alpine plants appeared to be well within desired conditions. There was no evidence of
recent bedding, salting or sheep trailing in the “restricted area” polygon. For this reason, design
criteria applied under Alternative 3 should provide for continued gradual improvement in butterfly
habitat conditions over time.
CUMULATIVE IMPACTS
Intensive historic levels of livestock grazing, increasing levels of jeep and OHV traffic on most
roads in the landscape, development of private lands within surrounding Federal lands, water
diversion, and 100 years of surface and subsurface mining operations have likely contributed to
substantial cumulative effects in lynx and flycatcher habitat. Some of the impacts of these past
activities have been reduced or mitigated through natural re-vegetation of formerly impacted areas
and improvements in water quality as abandoned mines have been reclaimed.
Mining was the past human activity that likely had the most extensive and negative impact on lynx
and flycatcher habitat conditions through out the Silverton Landscape. The effects of more than 100
years of mining have likely been extensive and heavy on willow distribution and structure in the
upper Animas River basin. For example, prior to the advent of mining in the late 1800’s, areas such
as the upper main stem of the Animas River between Howardsville and Eureka probably provided
extensive willow stands capable of supporting flycatchers. Willow stands are gradually revegetating
portions of this area, though the process is slow and few areas yet meet the definition of
flycatcher habitat. Many of the small stream headwaters and upper drainage basins were also
heavily impacted by mining, mostly in the form of water degradation due to mine waste runoff
significantly altering downstream vegetation structure and composition and carrying substantial
quantities of toxic metals that can affect wildlife species and habitat capability directly and indirectly
(Larison et al. 2000). Today, water quality and downstream vegetation structure have been
substantially improved by reclamation activities but remain impaired to varying degrees by mine
tailings and acid runoff from draining adits. Many of these point sources of water quality
degradation are on privately owned lands, and many are long abandoned mining claims on lands
now managed by Federal agencies.
Currently, development of private lands within a surrounding matrix of primarily public lands is
occurring at an increasing rate and is contributing to increased cumulative effects on wildlife habitat
capability and connectivity across the broader Silverton landscape. Most developments are single
family homes for use during snow free seasons. Many of these new recreation residences are being
built in the spruce-fir and alpine habitat types. In addition to increased human presence and activity
in areas formerly removed from human settlement, recreation residences also result in small losses
of primary habitat for listed species. The footprint for most of these residences involves the home
itself, a small cleared or heavily used area around the home, and an access road of varying length
across a steep hillside from an adjacent county road that services the home. Although most use of
these homes is during the snow free seasons, some are also used in winter as overnight huts for
backcountry skiers and snowmobilers and personal recreation by the owners. The residential
development that has recently occurred in the alpine zone does not appear to be affecting domestic
sheep grazing practices or patterns on surrounding federal lands but increased human presence in
winter has resulted in declines in winter habitat capability for some wildlife species. The rate of
development of privately owned parcels in the immediate vicinity of the town of Silverton appears to
be stable or increasing over the past five years as the economy of the town continues to gradually
expand. The amount and distribution of motorized recreation in winter is expected to continue to
gradually expand with corresponding gradual reductions in habitat capability for some wildlife
species. Cumulatively, the proposed action may offset some expected impacts from continued
increased winter use by gradually improving summer habitat conditions for listed species.
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