Submitted by Becca Hatheway on September 11, 2015 - 6:44pm

This blog post was contributed by Kateryna Lapina, an atmospheric chemist working at the University of Colorado Boulder, Department of Mechanical Engineering. In her work she uses chemical transport models to estimate the negative impacts of ground-level ozone on vegetation, including the loss of major agricultural crops and ozone-sensitive tree species in the U.S.

You may have heard about phytotoxic pollutants. The word “phytotoxic” is derived from the Greek word “phyto” (plant) and means being poisonous to plants. Harmful effects on vegetation were discovered as early as 1950s and now ozone is considered to be one of the most phytotoxic air pollutants. Not all negative effects of ozone are as easily observed as the leaf damage on the plants in our gardens. A reduction in plant growth and changes in chemical composition take place, too. Since two out of four plants in the garden are crop varieties, it is easy to understand why we should be concerned – these plants are the source of our food. In fact, many agricultural crops are sensitive to ozone pollution.

Leaves of a bean plant with brown patches indicating ozone damage

Ozone damage can be seen on these bean plants.
Credit: Danica Lombardozzi/National Center for Atmospheric Research

Effect of ozone on crops

This graph shows the ffects of ozone on the productivity of crops.

How important is the effect of ozone on crops? It turns out it is quite large. For example, a research study published last year showed that ozone pollution in India kills enough wheat and rice crops to feed 94 million (about one third of the country’s poor). And, worldwide, scientists have estimated an economic loss in the range of $14-26 billion for only four major agricultural crops – wheat, rice, soybean and maize – in the year 2000.  Losses like this can offset a major portion of the gross domestic product (GDP) for countries whose economy is based on agricultural production.

In addition to being a threat to food security, ozone exposure leads to other negative effects on vegetation, including a reduction in harvest of commercial timber and implications for climate change. The latter is due to a reduction in ecosystem carbon uptake, which results in additional carbon dioxide accumulation in the atmosphere.

How ozone affects plants

This diagram shows how ozone may affect plants and ecosystems.

For all of these reasons, cleaning up ozone pollution has a wide range of benefits for our society, including the economy, food security, and climate change.