Joshua
Tree National Park is immense, nearly 800,000 acres, and
infinitely variable. It can seem unwelcoming, even brutal
during the heat of summer when, in fact, it is delicate
and extremely fragile. This is a land shaped by sudden
torrents of rain, strong winds, and climatic extremes.
Rainfall is sparse and unpredictable. Streambeds are usually
dry and waterholes are few. Viewed in summer, this land
may appear defeated and dead, but within this parched
environment are intricate living systems waiting for the
opportune moment to reproduce. The individuals, both plant
and animal, that inhabit the park are not individualists.
They depend on their entire ecosystem for survival.
Two
deserts, two large ecosystems primarily determined by
elevation, come together in the park. Few areas more vividly
illustrate the contrast between “high” and “low” desert.
Below 3,000 feet (910 m), the Colorado Desert, occupying
the eastern half of the park, is dominated by the abundant
creosote bush. Adding interest to this arid land are small
stands of spidery ocotillo and cholla cactus. The higher,
slightly cooler, and wetter Mojave Desert is the special
habitat of the undisciplined Joshua tree, extensive stands
of which occur throughout the western half of the park.
Joshua
Tree National Park consists of 800,000 acres set aside
to protect the unique assembly of natural resources brought
together by the junction of three of California’s
ecosystems. The Colorado Desert, a western extension of
the vast Sonoran Desert, occupies the southern and eastern
parts of the park. It is characterized by stands of spike-like
ocotillo plants and “jumping” cholla cactus.
The southern boundary of the Mojave Desert reaches across
the northern part of the park. It is the habitat of the
park's namesake: the Joshua tree. Extensive stands of
this peculiar looking plant are found in the western half
of the park. Joshua Tree's third ecosystem is located
in the western most part of the park above 4000 feet.
The Little San Bernardino Mountains provide habitat for
a community of California juniper and pinyon pine.
The
plant diversity of these three ecosystems is matched by
the animal diversity, including healthy herds of desert
bighorn and six species of rattlesnakes. Joshua Tree National
Park lies astride the Pacific flyway of migratory birds,
and is a rest stop for many. It was for this unusual diversity
of plants and animals that Joshua Tree National Monument
was set aside on August 10, 1936.
The
park also encompasses some of the most interesting geologic
features found in California’s desert areas. Exposed
granite monoliths and rugged canyons testify to the tectonic
and erosional forces that shaped this land. Washes, playas,
alluvial fans, bajadas, desert varnish, igneous and metamorphic
rocks interact to form a pattern of stark beauty and ever
changing complexity.
Except
for the occasional spectacular wildflower bloom, the desert
appears to the casual visitor as an unchanging landscape.
In reality it is a dynamic, constantly shifting ecosystem.
Wind and rain have had the greatest effect in shaping
this ecosystem. If global warming is occurring, the desert
may get more rain.
Geologic
processes are continually at work as well, but are so
slow that we only notice their presence in the occasional
earthquake. While Wildfire and human caused factors such
as air pollution and off-road vehicle use can change the
landscape very quickly.
The
park is a "living laboratory" that helps us
understand how environmental factors have shaped this
desert ecosystem and how they may be changing it at present.
It also shows the sharp contrast between a less-disturbed
ecosystem and the completely human-shaped one in the urban
areas nearby.
Park
staff carefully monitor the effects of changes in air
quality, and the effects of nitrogen deposition, wildfires,
and invasion by nonnative plant species. Their watchful
eyes can alert managers and the public to threats to desert
resources in time for useful action.
