Agriculture: Ozone levels lead to losses in California’s perennial crops

Ozone levels have had a negative impact on the yield of many of California’s perennial crops, leading to an estimated loss of US$1 billion per year, according to a modelling paper published in Nature Food.

Changes in temperature and air pollution affect agriculture productivity, but most relevant research has focused on major annual crops, such as wheat, soy and rice. However, relatively little is known about the effects of climate change and air quality on perennial crops, such as fruits and nuts, which are important to dietary diversity and nutrition and represent around 38% of California’s agriculture by economic value. California produces over 400 agricultural commodities, supplying two-thirds of USA’s fruits and nuts, and over one-third of its vegetables. In 2015, the state’s agricultural output was valued at almost US$60 billion.

Chaopeng Hong and colleagues used historical data on ozone levels, temperature and crop yields gathered between 1980 and 2015 and found that ozone, more than temperature, reduced yields of table grapes, wine grapes, strawberries, walnuts, freestone peaches, nectarines and hay. Table grapes (generally eaten raw) were the most affected, with estimated yield losses of about 22%. This may be explained by the grapes’ exposure to the high ozone levels of the San Joaquin Valley.

The authors also demonstrated that reductions in ozone over time have improved crop yield, although losses remain large. They suggest that air quality regulations in California during this time may have been responsible for this change.