Scientists Are Trying to Save Salad From the Drought

Lettuce is more than 95 percent water—and arid California grows nearly all of the domestic supply.

Lettuce farm in Salinas, California. (Photo: Doug Steakley/Getty Images)

Aug 24, 2015· 2 MIN READ
Tove Danovich is a journalist based in Portland, Oregon.

For the last four years, California has been dreaming of water. Gov. Jerry Brown officially declared a state of emergency in 2014, followed by a mandatory water reduction of 25 percent in urban areas. But the water saved by digging up lawns and installing new showerheads hasn’t helped farmers, who have let an estimated 540,000 acres of land go fallow, resulting in a total economic loss of $2.7 billion, according to a report by the California Department of Food and Agriculture.

Even if El Niño shows up as predicted, it’s not a long-term solution for many crops. The National Oceanic and Atmospheric Administration recently published a report showing that combined global temperature in July was the highest in 136 years of recorded data. And a wet winter doesn’t mean the drought will end. So rather than praying for rain, scientists have started work on a number of drought- or flood-resistant crops that will hopefully make agriculture in California (and beyond) more resilient.

Though many of the drought-tolerant varieties under development are commodity crops such as rice, wheat, or corn, the high water content of the delicate vegetables grown up and down California makes their fate iffier during water shortages. A USDA research project based in California is attempting to develop a drought-resistant variety of lettuce. At about 96 percent water, the green has one of the highest water-content levels of any type of fruit or vegetable. Renee Erikson, a plant research geneticist working on the breeding program, said the crop was of particular interest because California produces 72 percent of head lettuce and 85 percent of leaf lettuce grown in the United States.

The first step in the process is combing through various cultivars of lettuce, looking for traits that might make it able to tolerate a lower water input. From an initial 3,500 varieties observed in the greenhouse, 200 varieties were taken outside for field trials, Erikson said. She takes an even smaller sample of them, about four at a time, to look at the physiological traits that might make this or that lettuce a good candidate for breeding.

“We’re not going to be able to achieve the kind of drought tolerance you might see in a drought-tolerant wheat variety,” Erikson said. “Lettuce doesn’t taste good when it’s dry.” Instead, she and her colleagues are hoping to develop a variety that takes “a little bit less water” and pair it with more efficient irrigation. The results won’t be drastic—don’t expect dry-farmed romaine—but in aggregate, it may be enough to cut down on water usage on the more than 200,000 acres of lettuce farms across the state.

California isn’t the only place where people are worrying about water usage. Agricultural research centers around the United States have developed heat- and drought-tolerant beans, cowpeas (a major source of protein in many parts of the world), soybeans, and more. Internationally, countries are also taking care of their own. In 2014, East African scientists released 10 varieties of drought-tolerant maize. China may finally have found success developing a perennial variety of rice that not only tolerates temperature and water fluctuations but also requires less soil disturbance to grow.

Last year, the journal Nature Climate Change published a study that estimated the four major global staple crops—wheat, rice, maize, and soybeans—will face a drop of 10 percent or greater in production by 2050 owing to rising temperatures. That’s in conjunction with a 50 percent rise in global demand for food, as the authors of the study point out. Temperature and water fluctuations aren’t the only issues plants may have to contend with in the decades to come. Some plants are susceptible to elevated levels of ozone, a toxic gas formed most notably by ultraviolet light. Daniel Taub writes in Nature that high concentrations of ozone can cause tissue damage to leaves as well as decreased plant growth and photosynthesis.

Drought-tolerant strains aren’t magic, but they’re an important step toward developing more sustainable agriculture. Still, the process can be long, depending on the growth time of the plant. While a full head of lettuce takes four to eight weeks to reach maturity, orchard crops such as peach trees may take two to four years to bear fruit. It often takes many generations before conventional breeding can consistently conjure a plant with desirable traits. The simple lettuce plant may be in the water-starved grocery stores of the future while the almond, the peach, and the cherry linger in the lab.