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For California’s fruit trees, 2021 It was a dry year. Nearly 90% of the state was affected by extreme drought. More than 70,000 farms, which grow a third of the country’s fruit and nuts, including $6 billion worth of almondsEach year, nearly $1.6 million worth of pistachios is collected by on reduced water rations.
By all indications, these severe water shortages are just a taste of what’s in store as weather patterns grow more extreme. The average life span of fruit and nut trees is 40 to 50 years. This means that they must be able to withstand any climate change in the next half century.
“I’ve compared it to two great battles in World War II: You had D-Day, which was a frontal assault, and Dunkirk, which was a strategic evacuation,” says Pat J. Brown, a plant breeder who is also a professor of plant sciences at UC Davis. Scientists have already begun to stockpile the lifeboats in response to our rapidly warming planet. “With climate change, for a while we were talking about stopping it from happening. Now, we’re talking about adapting to it.”
Enter the “torture orchard,” the cheeky nickname for 80 acres of the Wolfskill Experimental Orchards where researchers see exactly how much abuse 20 varieties of trees can take. The goal is to create a new generation of pistachios, almonds, walnut, pomegranate and other fruit and nuts trees that can withstand droughts.
“The origin of the ‘torture orchard’ was we had a bunch of pistachios that we established in the fall, then we ripped up the irrigation in May and didn’t water them all summer,” Brown says. “The idea was to see who lives, who dies. That was extreme torture.” It turns out that pistachio trees are especially resistant to drought and the resulting high levels of salinity in the soil. “[The experiment]They all survived, so it was a bit of a failure. We didn’t kill a single one.”
While those results sound promising for pistachio-lovers, we don’t yet know whether they will hold in a commercial orchard. That’s because both the conditions and plants differ dramatically from an actual fruit orchard. Instead of growing a whole tree from one seed, commercial orchards use a rootstock. This is essentially a stump and root system that has been grafted with a scion taken from a genetically different tree.
“You wouldn’t enjoy eating the pistachio nuts from the trees we had in the torture orchard, because they’d be tiny,” Brown explains. “In a commercial situation, you divide and conquer. You have one species that you use for the rootstock that you can breed for drought resistance or salt tolerance, but for the top, for the scion, you can use something that will produce big, tasty fruit or nuts.”
These Frankenstein trees’ rootstocks are usually derived from a few genetically identical clones. Brown estimates that on California’s 312,000 acres of pistachio trees, there are only a half-dozen genetically distinct rootstocks. “The exciting thing about genetics and breeding is that these innovations can be completely free to everyone,” Brown says. “If we find a DNA variant that lets you use five percent less water, we’re basically getting that for free from the point of view of the planet.”
If he and his colleagues can identify the rootstocks’ pressure points and develop even a few new varieties, it could help save the industry. Whether it’s high levels of salt or boron in the soil, those weak spots are different for each species of tree. The high-salinity trial in which the pistachio tree survived successfully killed every walnut tree.
“Every tree has its Achilles’ heel when it comes to climate change and sometimes it might be tough to predict,” Brown says. “We should be worried about pistachios from the chilling perspective. A lot of these deciduous trees need winter cold in order to flower properly in the spring.”
Pistachio trees aren’t alone in their need to hunker down through the cooler months of the year. Trees contain a multitude of different species, and more research is done to prove it. We now know that trees communicate through their leaves. subterranean fungal networksIt turns out that 47,000 quaking Aspens share a single root system. single largest organism in the worldTrees, just like humans, need their rest.
“We think of trees as dormant in the winter, but their metabolism inside is churning away,” says Ken Shackel, a plant scientist and professor at UC Davis. Like Brown, Shackel jokes that he “tortures plants for a living,” although since he routinely works in growers’ orchards, he usually tries not to murder them. “Just because something looks like it’s sleeping doesn’t mean that it’s not busy. The dormancy is an adaptation of the trees for waiting out the winter.”
Shackel compares the process with bears who go into winter torpor. Humans used to believe that bears slept for seven months. Researchers placed cameras in their dens and discovered that this was not the case. was far from the case. These periods of low activity are used by deciduous trees, just like mammals, for a host of biological functions.
“As things get warmer in the winter, they may burn out of their reserves and have nothing left in the springtime to blossom,” Shackel says. “That would be catastrophic for fruit trees.”
One of Shackel’s most troubling findings is that the ramifications of severe drought or other problems can last for multiple seasons. Although the stressed-out trees did produce some flowers in the spring, they were not able to produce as many the following year. “The next year, when you see the carry-over effect, then you actually have almost double the reduction in yield,” Shackel says.
In order to measure the amount of stress trees are under, Shackel developed a pressure bomb—so named because earlier iterations of the contraption looked like a bomb calorimeter—to measure the botanical equivalent of blood pressure. “Trees don’t have blood, they have water under pressure, but it’s still the same principle,” Shackel says. “Our heart pumps blood using pressure and trees get water out of the soil through suction.” Using the device, Shackel and his fellow bombardiers found that under drought conditions the “blood pressure” of the almond trees soared to roughly four to 12 times the normal level.
Despite all the research underway, Shackel worries that growers aren’t taking the threat of water shortages seriously enough. Growers might soon have to rely on water from cities that is of lower quality. Some trees require so many water that it is difficult to transport. “Even the recycled water from Los Angeles might be a drop in the bucket for a hundred-acre almond orchard.”
The problem with climate change is that people don’t want to spend their money now on problems for tomorrow. “Growers prefer that politicians just give them the water that they need, but it may be that there just won’t be enough water to go around,” Shackel says. “There’s a fear of the unknown because of the risk of adopting a new variety. If you have a new tomato or wheat variety, you can try it for a year and if it doesn’t work out, no biggie. With a tree, you’re making an investment for the next couple of decades.”
He believes that not all news is bad. California’s varied geography and latitudinal sprawl make the state well-positioned to keep growing a diverse array of crops. Napa’s vineyards and almond trees may need to move north. Trees are very adaptable, much like humans, provided they have the time to adjust. “I’m of the opinion that plants just don’t like surprises,” Shackel says. “If something happens slowly, they function at a lower level, but they’re pretty good at surviving as long as something doesn’t hit them like a ton of bricks.”
Researchers are concerned about the ton-of bricks scenario, which is the sudden onset extreme drought or weather conditions. One single shock can have devastating consequences, as the torture tree demonstrates. Shackel and his colleagues envision a future where humanity can thrive on a variety of food sources that include fruit and nuts. Climate scientists tend to concentrate on increasing production when discussing food security in dystopian nightmares like those envisioned by writers like Octavia Butler and Paolo Bacigalupi. utilitarian crops like corn, wheat, rice, and soybeans.
“I don’t want to sound like a survivalist, but push comes to shove, you need carbohydrates, calories, and maybe some protein,” Shackel says. “If it gets to that, maybe we’ll all be eating Soylent Green.”
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