Scientists say that in the next couple of decades, as temperatures heat up and greenhouse gas levels elevate, fruit and nut harvests will not only get smaller, but many of the grains, including wheat, and other ground crops we grow will lose some of their nutrients: protein, iron, and zinc. What that means is that nutrient-dense foods such as produce, nuts, and cereal will become less plentiful and more expensive, and the changes will alter our diets—for the worse.
Experts predict that developing countries, where protein is at a premium, will be more affected than the western world, where diets are more varied.
At least for now.
As UC Berkeley alum Marion Nestle, author and a respected nutrition professor at New York University, puts it: “Even if the differences don’t matter much in the immediate future, the long-term prospects are not good.”
Right now, the big worry is having enough food to eat and preserving California’s core economy: agriculture. It’s a $45 billion business that also generates billions more in other state-related industries.
“My concern is whether California farmers will be able to survive,” says Katherine Pope, who is Area Orchard Systems Advisor for Sacramento, Solano, and Yolo Counties. While a graduate student at UC Davis, Pope analyzed 60 years of weather patterns and their effect on fruit and nut trees, specifically California English walnuts. She found that around 1970, temperatures started growing increasingly higher. Initially, as springs got warmer and warmer, trees responded by flowering earlier. But more recently, the walnut leaf buds began opening later—a phenomenon Pope attributes to the fact that the results of warmer winters are now outpacing the ramifications of warmer springs.
“All trees in California’s Central Valley that lose leaves, including walnuts, pistachios, cherries, certain varieties of peaches, and prunes, have to experience some winter chill to bear fruit,” explains Pope. “If they only get a marginal chill, the buds will open, but they won’t bear fruit. We’re seeing longer bloom windows and lower crop yields.” This winter, for example, was one of the driest in close to 100 years, she says. The cherry crop, worth about $200 million a year to California, was one of the worst harvests ever. Of course California’s devastating drought may also be to blame, Pope suggests.
“It’s kind of a perfect storm,” she says. “But from a climate change perspective, this is a great example of everything bad that we’re expecting to happen.”
Despite her less than positive findings, Pope is optimistic that innovation—breeding new varieties of trees that will hold up better to the warmer winters, which may become the new norm—will eventually save the day.
Jack Mariani, a Winters (Yolo County) farmer and cofounder of the Mariani Nut Co., one of the largest walnut and almond processing plants in California, has spent his life watching the weather. His business depends on it. He’s somewhat circumspect, given the number of variables to climate forecasting. However, even he allows that recent winters “could be a telltale sign” of a dismal future.
“Cherries this year?” he says. “Well, it was even hard to find one on a tree.”
He says that the weather was a likely culprit for the poor cherry harvest, but farmers are still taking a wait-and-watch approach to see if the trend persists. In the meantime, they’re tracking any new technologies coming down the pike that may work in combating climate change. Scientists such as Pope are working on these improvements, but they could be a long way out.
“Everyone [in farming] is cognizant of what’s going on,” Mariani says. “But once you have your trees in the ground, there’s not a lot you can do.”
And Dennis Baldocchi, a Berkeley researcher and biometeorologist, thinks it’s going to get worse. The professor of Environmental Science, Policy, and Management has studied and reported on how the Central Valley’s tule (pronounced “too-lee”) fog, a thick shroud of mist that helps keep trees cool from late fall to early spring, has dramatically declined in the past three decades.
Baldocchi says he started the fog study back when then-governor Arnold Schwarzenegger commissioned a group of Berkeley professors to look at the effects of climate change on California. Being the son of an Antioch and Oakley almond and walnut farmer, he naturally gravitated to researching the agricultural consequences of global warming. Plus, his cousins, Central Valley cherry growers, had noticed a correlation between low harvests and unseasonably warm winters.
So he went back 32 consecutive winters and looked at weather data collected by NASA and the National Oceanic and Atmospheric Administration. Although there was a significant variability in fog levels from year to year, he and other researchers discovered a 46 percent drop, on average, in the number of foggy days in the valley.
“The good news is that there are fewer car accidents related to poor visibility,” Baldocchi says. “The bad news is that the trees need this dormant time to rest so that they can later develop buds, flowers, and fruit during the growing season. Without a sufficient rest period, fruit yields suffer.”
He says, too, that the weather change raises a red flag for the state’s multibillion dollar agriculture industry. Baldocchi reports that other studies have shown the decline of winter chill in the valley—since the 1950s, the number of cold hours has dropped by several hundred. But air temperatures alone may not be an accurate measure of how much heat the crops are absorbing. He says direct sunlight can heat the buds, making them warmer than the actual temperature reading outside.
“That’s why the fog is so important,” he says. “[It] shields the buds from the sun and helps them stay cooler.”
On the ground, another host of problems has been found by Arnold Bloom, professor and plant scientist at UC Davis. For the first time, tests show that elevated levels of carbon dioxide are affecting protein levels in plants. Carbon dioxide, a greenhouse gas that traps heat into the atmosphere, has increased 35 percent since 1800, according to the United Nations’s Intergovernmental Panel on Climate Change. Experts predict that CO2 levels could reach 970 parts per million (ppm) by the end of the century. As of last year, they hovered around 400 ppm. Recently, NASA launched a satellite into space to regularly measure CO2 levels in the atmosphere, in order to better predict how carbon dioxide is contributing to global warming.
For Bloom, the effect on wheat and other ground crops is clear: CO2 inhibits plants’ assimilation of nitrate into proteins, demonstrating that the nutritional quality of food crops is in jeopardy as climate change intensifies. “We looked at nearly every food crop, including wheat, barley, rice, maize, potatoes, peas, and soybeans, and the results—a decline of protein levels—were pretty universal,” Bloom says. “We even saw it to a slight degree with corn.”
Bloom estimates that in the next few decades, consumers can expect grains to lose 8 percent of their protein. Wheat in particular will be a problem, because it provides one-fifth of all protein in the world’s human diet.
“When this decline is factored into the respective portion of dietary protein that humans derive from these various crops, the overall amount of protein available for human consumption may drop by about 3 percent as atmospheric carbon dioxide reaches the levels anticipated to occur in the next 20 to 40 years,” Bloom says.
A more recent study led by Harvard researchers (Bloom was a contributor) also found that grains and legumes had a lower concentration of iron and zinc when grown under field conditions where the atmospheric CO2 was elevated to levels between 546 and 586 ppm. Wheat grown at these elevated carbon dioxide levels lost 9.3 percent of its zinc and 5.1 percent of its iron as compared with wheat grains grown at ambient CO2 levels, according to the study.
This diminishment is also of major concern, Bloom says, because dietary deficiencies of zinc and iron are a sub-stantial global public health problem. An estimated 2 billion people suffer these deficiencies, causing a loss of 63 million life-years annually, according to the study. Since wheat, rice, barley, oats, millet, rye, and legumes are a primary source of zinc and iron, people will have to turn to other, often more expensive sources.
Kristen Rasmussen, a nutritionist and lecturer in Berkeley’s Nutritional Sciences and Toxicology Department, says that although iron deficiencies in the United States are a problem, Americans already get more than enough protein. On average, people need about 60 grams of protein a day, she says, adding that Americans take in about 1.5 times that amount.
That doesn’t mean, however, that Bloom’s study isn’t cause for concern, she cautions. Nestle agrees, saying, “It looks like an impressive study to me, carefully and thoughtfully done. And it’s based on real studies, not just models.”
Although Bloom’s findings may be a bigger problem for less-developed countries where the population has protein deficiencies, Rasmussen points out that all diets should pack a hearty nutritional punch. “We’re always encouraging people to eat nutrition-dense foods and less empty calories,” she says. “If the nutritional quality of our food is declining, then we’ll be doing just the opposite: taking in more calories without the added health benefit.”
Scientists haven’t found the same nutritional decline in tree crops. But if there are fewer fruits and nuts—considered among the world’s most healthful foods—to go around, that too will take its toll on the human diet. Not to mention the California economy.
Another unknown, says Katherine Pope, is whether climate change is likely to affect the taste and texture of produce and grains. “No one has tested that,” she says, “at least not that I know of.”
So what’s the solution?
California farmers will have to adapt—in many cases replanting entire fields with new breeds of fruit and nut trees that can withstand warmer winters, according to studies done by both Berkeley and UC Davis. This, however, would likely take 40 or so years, warns Pope.
“We do have a pretty good sense [of] which trees are going to be more vulnerable,” she maintains. “There are old varieties that require less cold factor, that have not been grown for various reasons. But if we put our heads together, we can come up with new varieties. This is not some controversial GMO answer. We’re not talking about taking a gene from a salmon and putting it into a walnut tree. We’re talking about classic breeding.”
Baldocchi has another suggestion for growers: Relocate. “Farmers may have to move the location of their orchards to follow the fog,” he says, adding that there are still places along the Sierra foothills where you can find the ground fog de-scending over the land. It would be a big and costly move, he acknowledges. “But we better start thinking about it now.”
In the meantime, scientists are looking at hormone and chemical sprays—some that have not yet been approved by the Food and Drug Administration—that can fake a tree into believing that it’s getting the proper amount of chill factor to make fruit. Mariani, the farmer, doesn’t know quite how he feels about the sprays, although he’s been paying attention to the research.
“Consumers have spoken, and the trend is certainly to be more natural or organic,” says Mariani, adding that chemicals likely wouldn’t play well on the market. “But then again, farmers wouldn’t use any chemicals at all if they felt they didn’t have to.”
As far as ground crops, says Bloom, heavy nitrogen fertilization could partially combat a decline in food quality, but it would cost more, leach into groundwater, and further increase greenhouse gas emissions. The rise in carbon dioxide is mitigated to some degree by plants when, through photosynthesis, they convert atmospheric CO2 into carbohydrates and other organic compounds. But whether protein limitations will change the extent of this mitigation remains to be seen, Bloom says.
Admittedly, neither spraying nor heavy fertilization seem like optimal fixes. But given that California produces more than half of the nation’s fruit and nuts—about 16.7 million tons a year—and since the United States is ranked third in the world for wheat production—roughly 58 million tons annually—some say we may, at least for now, have no other good options.
Stacy Finz is a former reporter for the San Francisco Chronicle. Her first novel, Going Home, is due out in October.