Environmental Engineering Reference
In-Depth Information
Bahre 26 summarizes the early impact on forests:
None of the sky island evergreen woodlands and forests was pristine before they were
set aside as forest reserves and national forests. By 1900, nearly all had been affected to
some degree or another by mining, logging, fuelwood cutting, and grazing. At present,
we have little idea what these woodlands and forests would be like had they not been
logged or grazed, had the fire regimes not been manipulated, or had Forest Service
management not occurred.
After World War II, commercial saw timber operations increased on the Gila and Apache
National Forests, as they did throughout the National Forest System. 50 Current overstock-
ing of forests was created purposely by the USFS and industry to maximize tree growth
for fiber production. They wanted to eliminate old-growth forests and replace them with
what they believed were “more efficient young forests”.
Old-growth ponderosa pine forests are listed as one of the 21 most endangered ecosystems
in the United States (Figure 10.8). 23 For all Arizona and New Mexico National Forests, the
Southwest Forest Alliance reports, “About 90 percent of the old-growth has been liquidated,
including 98 percent of the old-growth ponderosa pine.” Wallace Covington, forestry
professor at Northern Arizona University, says, “I've made it clear for 20 years there's been
a population crash of old-growth trees—leave the damn things alone.” He also writes, “The
cumulative effect of old-growth logging, non-native species introductions, overgrazing,
predator control, and fire exclusion has been ecosystem simplification so great that
Southwestern forest ecosystems are at risk of catastrophic losses of biological diversity.” 11,24,51
Seventy-three percent of the natural forest ecosystems of Chihuahua and Sonora have
been severely altered. 52 From the original 23 million acres occupied by old-growth pine-
oak forests in Mexico, only 0.6% (41,000 ac) remains. 22 This in turn has led to the decline
of species dependent on the old-growth forest, like the extinct imperial woodpecker and
the endangered thick-billed parrot and Mexican spotted owl. 53 Nearly all the Sierra Madre
Occidental has been logged at some point, and because of this, the present vegetation may
be different from the original cover. For example, small oak forests surround large (over
100 ft high) conifer trees, reminders of the forest that once was.
FIGURE 10.8
Old growth ponderosa pine is critical habitat for several threatened and/or endangered wildlife species, like
the southwest spotted owl and goshawk.
Search WWH ::




Custom Search