An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Ground-level Ozone Pollution

Ecosystem Effects of Ozone Pollution

Ozone can affect sensitive vegetation and ecosystems, including forests, parks, wildlife refuges and wilderness areas.  Ozone can especially cause damage during the growing season. 

What plants are at risk?

Plant species that are sensitive to the effects of ozone on their growth include trees found in many areas of the U.S., such as:black cherry tree damaged by ozone exposureblack cherry

  • black cherry
  • quaking aspen
  • tulip poplar
  • white pine
  • ponderosa pine
  • red alder.

What does ozone exposure do to sensitive plants?

When sufficient ozone enters the leaves of a sensitive plant, it can:

  • Reduce photosynthesis, which is the process that plants use to convert sunlight to energy to live and grow.
  • Slow the plant's growth.
  • Increase sensitive plants' risk of:
    • diseasediseased tulip poplar leaftulip poplar
    • damage from insects
    • effects of other pollutants
    • harm from severe weather.

Also, some plants can show visible marks on their leaves when ozone is present under certain conditions.

What happens to the ecosystem?

The effects of ozone on individual plants can then have negative impacts on ecosystems, including:

  • loss of species diversity (less variety of plants, animals, insects, and fish)
  • changes to the specific assortment of plants present in a forest
  • changes to habitat quality
  • changes to water and nutrient cycles.