Healing the Wounds: An Example from the Sky Islands - Design with the Desert: Conservation and Sustainable Development - page 199

FIGURE 10.5
Habitat fragmentation from residential development and in the foreground is a major pipeline that bisects
many miles of Arizona landscapes from woodlands, interior chaparral, and into the Sonoran Desert.
At certain scales, isolation of habitats can contribute to native biodiversity. At the land-
scape or regional scale, the higher elevations of the Sky Island ranges are naturally iso-
lated, 38 permitting genetic divergence and speciation. However, native species using
stream and riparian habitats and wide-ranging species such as carnivores, large ungu-
lates, and migratory birds need natural connectivity in the landscape. This natural con-
nectivity has been severed during the last century. Soulé and Terborgh 39 remind us that
“connectivity is not just another goal of conservation: it is the natural state of things.”
Coolidge Dam on the Gila River, Presa de la Angostura on the Rio Bavispe, and Presa del
Novillo on the Rio Yaqui; smaller dams on headwater streams of the Gila, San Francisco,
Santa Cruz, Janos, and other rivers; irrigation diversion dams; and dewatered and degraded
stretches of once-perennial streams have fragmented the habitat for native fish, amphib-
ians, and aquatic invertebrates. Habitat loss and degradation of bosques have harmed
riparian-dependent birds and other species. Habitat for wide-ranging species such as wolf,
mountain lion, jaguar, pronghorn, and bighorn has been fragmented by roads, agriculture,
and urban, suburban, and ranchette development.
Interstate Highways 10 and 19 are formidable barriers to many kinds of wildlife.
Increased traffic on and the proposed widening of Mexico Highway 2 will make it a sig-
nificant barrier too. Even two-laned paved roads cause many deaths of animals trying to
cross. Dirt roads fragment the landscape for wolves, jaguars, and other species vulnerable
to opportunistic poaching. For example, at least five released Mexican wolves were shot
alongside roads in the Apache National Forest in 1998. Even dirt tracks can fragment the
landscape for slow-moving desert tortoises and snakes, especially when many off-road
vehicle enthusiasts deliberately run over reptiles for thrills.
In Mexico, public access to private ranches is more open than in the United States,
and the access to ejidos (community lands) is practically uncontrolled. Under this situ-
ation, roads are a permanent source of poaching. Although the northern Sierra Madre
Occidental does not have the industrial and agricultural infrastructure of the southwest-
ern United States, the landscape in Mexico is becoming increasingly fragmented because
of growing economic pressure in the region and conversion of natural vegetation to