National Wildlife Refuge System

Effects of Air Quality

Many resources and values at units of the National Wildlife Refuge System are affected by air pollution. For example, scenic vistas are highly dependent on good visibility. Poor visibility caused by air pollution can indicate that there may be other impacts occurring to sources that cannot be readily observed. Three major effects of air quality on a park include: visibility, ecological, and human health.


Visibility Effects

Visibility is one of the primary air-related attributes that people associate with wildlife refuges. Many visitors come to refuges to enjoy the spectacular vistas. Unfortunately, these vistas are sometimes obscured by air pollutants, especially fine particles in the atmosphere. The Fish and Wildlife Service monitors the visibility conditions, investigates the cause of visibility impairment, and works cooperatively with air regulatory agencies to remedy the impairment.

Visibility is affected by the physical interaction of light with particles and gases in the atmosphere. Visibility involves more than specifying how light is absorbed and scattered by the atmosphere and particles suspended, it is psychophysical process of perceiving the environment through the use of the eye and brains. As pollution within an area increase, visibility impairment will increase. This is shown in the pictures below as the left vista has no haze while the right vista is inhibited by local haze.

No Haze Visibility Haze Visibility


Ecological Effects

Air pollutants can harm ecological resources, including water quality, soils, plants and animals. Ozone, for example, causes foliar injury and reduced growth in some sensitive plant species as shown in the picture below. Atmospheric deposition of sulfur and nitrogen compounds can cause significant ecosystem effects such as acidification, eutrophication, and changes in soil and water chemistry. Acidification of soils, lakes and streams can result in changes in community structure, biodiversity, reproduction, and decomposition. Documented impacts in some refuges include stressed trees, acidified streams, and reduction in species of fish and other aquatic life in affected waters.

Although nitrogen is an essential plant nutrient, increased levels of atmospheric nitrogen deposition can stress ecosystems. Excess nitrogen acts as fertilizer, favoring some types of plants and leaving others at a competitive disadvantage. This creates an imbalance in natural ecosystems, and long-term effects of these changes may include shifts in types of plant and animal species, increase in insect and disease outbreaks, and disruption of ecosystem processes such as nutrient cycling, and changes in fire frequency.

Metals, such as mercury, and persistent organic compounds deposited from the atmosphere can bioaccumulate in the food chain, causing behavioral, neurological and reproductive effects in fish, birds, and wildlife.

Ozone Injured Plant


Human Health Effects

Human health effects associated with acute and chronic exposure to air pollution are well documented. Ozone and fine particulate concentrations in some areas have approached and exceeded the national health standards. Exposure to ozone can damage to lung tissue and increase the susceptibility of the lungs to infections, allergens, and other air pollutants. Short-term exposures to particulate matter may aggravate asthma, bronchitis, and may be associated with heart beat irregularities and heart attacks.

Last updated: June 16, 2015