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| On a clear day visitors to Joshua Tree National Park can see
the Mexican border from the mile-high vantage point of Keys View. More often,
visitors can barely discern the tip of 10,000-foot-high Mount San Jacinto,
about 50 miles away. |
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| The haze that obscures these vistas is the result of smog
that blows into the park from surrounding urban areas. Growth in the Coachella
Valley, and to a lesser extent in the hi-desert, and construction of power
plants nearby, all impact air quality in the park. But Los Angeles basin,
with a population over 12 million, is the major contributor of ozone and
other pollutants that reach the park. |
| Polluted air contains particulate matter that drops out nitrates onto
the soil. Desert plants that have adapted to survive in nitrogen-poor
soils
must now compete with non-native grasses and other exotic plant species
that thrive with the added fertilizer. Sparce desert vegetation is advantageous
when lightening strikes ignite fires in the park. Without abundant vegetation
to carry it, a fire will quickly burn out. When non-native plants thrive
in the park, they provide the fuel for larger, hotter fires that can burn
thousands of acres of slow growing Joshua trees, junipers, and pinyon
pines.
The non-native species are better able to reestablish themselves quickly
after a fire, increasing their abundance to the detriment of the ecosystem.
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| Although the Environmental Protection Agency (EPA) has mandated that
the skies above our national parks be subject to the most stringent level
of
protection, Joshua Tree National Park consistently exceeds the 120 ppb
ozone concentration levels set by the EPA for human health at it’s
monitoring station located in the northwestern part of the park. The park
would like
to install additional monitoring stations to determine if the entire park
is out of compliance with air-quality standards. |
| The park is also working with the University of California at Riverside
to determine how soil nutrients, carbon cycling, and the nitrogen supply
are affected by air pollution in the park. Native plants such as Rhus
trilobata are sensitive to high ozone levels and other animal species
are likely to be affected as well as humans. |
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http://www.nps.gov/jotr/nature/environment/airquality/airguality.html
last modified: 05/31/02
web editor: Sandra kaye |
