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Ground-level Ozone

Ecosystem Effects

Ozone Effects on Plants

image of black cherry damage

Recent systematic surveys by the USDA US Forest Service continue to document widespread injury on sensitive bioindicator plants.

Black Cherry
Courtesy, USDA FS FIA

image of leaf damage from ozone

Many studies have documented diagnostic leaf injury due to ozone in the field, including remote wilderness areas. However, damage from ozone is not always visible on leaves and growth decline can occur without these symptoms.

Tulip Poplar

image of tree and root system

Ground level ozone is absorbed by the leaves of plants, where it can reduce photosynthesis, damage leaves and slow growth.  It can also make sensitive plants more susceptible to certain diseases, insects, harsh weather and other pollutants.

Ozone also affects sensitive vegetation and ecosystems, including forests, parks, wildlife refuges and wilderness areas.  In particular, ozone harms sensitive vegetation, including trees and plants during the growing season. 

Plant species that are sensitive to ozone and potentially at an increased risk from exposure include trees such as black cherry, quaking aspen, ponderosa pine and cottonwood. These trees are found in many areas of the country.

Ground level ozone can have harmful effects on sensitive vegetation and ecosystems. When sufficient ozone enters the leaves of a plant, it can:

  • Interfere with the ability of sensitive plants to produce and store food.
  • Visibly damage the leaves of trees and other plants, harming the appearance of vegetation in urban areas, national parks, and recreation areas.

In addition to reduced tree growth and visible injury to leaves, continued ozone exposure over time can lead to increased susceptibility of sensitive plant species to disease, damage from insects, effects of other pollutants, competition, and harm from severe weather.  These effects can also have adverse impacts on ecosystems, including loss of species diversity and changes to habitat quality and water and nutrient cycles.

For more information on how EPA works to reduce ground level ozone, visit the Ozone Standards page.

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