AIR QUALITY IN JOSHUA TREE NATIONAL PARK

The following is adapted from material by Howard Gross of the National Parks Conservation Association.

Air Quality Problems

Congress designated Joshua Tree National Park as a Class I area under the Clean Air Act, which affords it maximum protection, by establishing as a national goal “the prevention of any future, and remedying of any existing, impairment of visibility…resulting from man-made pollution.”  Despite this designation, Joshua Tree’s air quality is among the worst in the National Park System with park ozone levels consistently exceeding the EPA’s human health standard.  In fact, the ozone levels in Joshua Tree National Park were worse in 2002 than all but seven of the most polluted major metropolitan areas in the nation. This air pollution frequently endangers the health of park employees and visitors, degrades the park’s scenic vistas, and deposits nitrogen compounds that benefit non-native plants, thereby disrupting the fragile desert ecosystem.

Hazy Scenic Vistas: On a clear day in Joshua Tree, visitors to Key’s View might see 100 miles south to Signal Mountain in Mexico or enjoy the spectacular 360-degree desert panorama from Mount Ryan.  However, nearby growing urban areas have contributed greatly to the deterioration of these views.  In fact, the vista from the Keys View is obscured by haze often enough that some park visitors have asked for reimbursement of their admission fee.

A major contributor to this impaired visibility is fine particulates in the air with diameters of less than 2.5 micrometers.  Known as “PM2.5,” these particulates result primarily from the burning of fossil fuels but also from burning vegetation and smelting and processing metals.  PM2.5 also poses a greater health risk than larger particulate matter such as PM10 because the smaller-sized particulates can go deeper into the respiratory tract.

Ozone: Ozone is a gas composed of three oxygen atoms (O₃).  When it occurs naturally in the stratosphere, it serves as a protective layer that filters out damaging rays emitted from the sun.  But when it occurs at ground level, it can create health problems for humans, wildlife, and plants.  Ground level ozone is formed when volatile organic compounds and nitrogen oxides—coming from automobile exhaust, industrial emissions, gasoline vapors, and chemical solvents—are exposed to sunlight, heat up, and react chemically.  The heated ozone rises to higher elevations and thus occurs at greater concentrations in Joshua Tree than in surrounding lower elevations.

Breathing ozone can cause irritation to the respiratory system including chest pain, coughing, throat irritation, and congestion.  It can worsen existing respiratory problems, reduce lung function, and cause permanent scarring of lung tissue.  Persistent exposure to low levels of ozone can also impact the immune system.

During the “ozone season,” from April through October, ozone pollution levels in Joshua Tree frequently exceed the EPA’s 8-hour human health standard, resulting in warnings for people to reduce outdoor activities.  The bitter irony in these warnings is that outdoor activities are precisely what people visit Joshua Tree and other national parks to pursue. Last year, these levels were exceeded 39 times in the park. The primary sources of the ozone pollution are vehicle emissions, power plants, and upwind urban areas such as the Los Angeles Basin.

Nitrogen Deposition: The air pollution in Joshua Tree contains particles of nitrogen that deposit onto the soil and act as a fertilizer. Since native desert plants have adapted to surviving in nitrogen-poor soils, the added fertilizer can benefit non-native grasses and other exotic plant species that disrupt the fragile ecosystem.  Since the park’s native plants are usually dispersed enough to keep the fires from spreading, additional fuel from the non-native plants causes park wildfires to be larger and hotter, such as that which occurred in 1999.

For More Information

To learn more and get involved in the effort to clear the air in Joshua Tree, please contact Howard Gross, the National Parks Conservation Association’s California desert program manager, at 760-366-3035 or by email at hgross@npca.org.