Healing the Wounds: An Example from the Sky Islands - Design with the Desert: Conservation and Sustainable Development - page 197

FIGURE 10.3
Degraded desert riparian wash showing accelerated streambank erosion.
species degraded wildlife habitat and led to greater erosion of channels. Agricultural
clearing along the Gila, San Francisco, Mimbres, San Simon, San Pedro, and Santa Cruz
rivers eliminated or degraded the most productive and extensive bosques. Water diversion
for irrigation and later for mining, the downcutting of arroyos (lowered streambeds in
arroyos intercept ground water at a greater depth, thus drawing the water table down),
and groundwater pumping for agriculture, mining, and urban use have lowered the water
table, resulting in dried-up cienegas (wet meadows), dewatered rivers, and dying bosques.
This loss of habitat and degradation of ecological resilience has encouraged the spread of
exotic species and the elimination of sensitive native species. Watersheds were damaged
not only by livestock grazing, but also by the widespread clearcutting of piñon ( Pinus ),
juniper ( Juniperus ), and oak ( Quercus) woodlands for mining timbers and fuelwood. 26
In the northern Sierra Madre Occidental of Chihuahua and Sonora, cattle freely graze
riparian areas. Especially in the lowlands, where there is little tree cover outside the
riparian areas, cattle have limited the growth of new trees, so when the old cottonwoods,
sycamores ( Platanus wrightii ), walnuts ( Juglands major ), and other riparian trees die, no
young trees replace them. Cattle do similar damage in Arizona and New Mexico.
Another problem in the riparian areas in Mexico is that the river bottoms are often turned
into access roads for timber exploitation. Related to this exploitation is the practice of throw-
ing sawdust and other byproducts from the lumberyards into the rivers, which adversely
changes the water quality, in turn affecting native fish and other freshwater species.
Too few have heeded Leopold's warning 3 : “Somehow the watercourse is to dry country
what the face is to human beauty. Mutilate it and the whole is gone.”
10.2.3 Wound 3: Elimination of Natural Fire
Causes: A natural disturbance regime vital to the health of forest, woodland, and grassland
ecosystems in the Sky Islands region has been largely eliminated by over a century of (1)
livestock grazing and (2) fire suppression.
Most ecosystems in the Sky Islands region coevolved with frequent fire. Only the
most arid Chihuahuan and Sonoran desert communities in the region are not adapted
to regular fire. Before about 1900, most montane forests burned in accordance with the