It’s now undeniable that climate change is imperiling the global food supply. Crops are increasingly threatened by drought, floods, and wildfire. And a recent study published in Science estimates that for every 1 degree Celsius of global warming, increased insect activity will reduce grain yields by 10 to 25 percent.
Climate change is also empowering a less familiar food foe: fungal pathogens. Molds and mildews thrive under increased precipitation and high carbon dioxide levels. Fungal pathogens are marching northward at a global average of about 4.3 miles per year, according to a study in Nature Climate Change. Another study published in Nature estimates that crops lost to fungi, and to their oomycete cousins, could feed more than 8 percent of the global population. And the situation will only get worse.
What can we do? Chemical fungicides have long been the go-to defense against fungal pathogens. But fungal blights adapt quickly, so dousing crops in fungicides is a losing strategy. Fungal blights are rapidly building resistance to the most commonly used agricultural fungicides and, as a result, the chemical treatments are yielding diminishing returns.
Fungicides also pose health risks. A 2016 study published in Nature found that some agricultural fungicides are associated with autism-like neurological symptoms. Perhaps wary of such risks, the public seems to have lost its appetite for chemically treated food: Sales of organic foods in the U.S. grew from $3.6 billion in 1997 to $43.3 billion in 2015, according to the Organic Trade Association.
Worse still, disturbing new evidence suggests that fungicide-resistant pathogens can be transferred from the fields to humans. One such pathogen, Aspergillus, commonly attacks the lungs of transplant recipients, patients being treated for HIV, cancer, and diabetes, and other people with compromised immune systems. Aspergillus is typically treated with a class of antifungal drugs known as azoles. But azoles have also been used liberally as fungicides for crops, and Aspergillus has become immune to them. That’s left doctors with few treatment options. According to a 2018 article in Science, “Azoles are increasingly failing as frontline therapies, with associated patient mortality approaching 100 percent.”
As fungicides lose potency, some experts have advocated for a lower-tech solution to the food security problem: a shift away from the “Big Ag” practice of monocropping, in which an entire plot of land is seeded with just a single kind of plant. Monocropping makes it easy for a single species of pathogen to destroy an entire harvest. It can take as little as two years for a fungus to develop resistance to a fungicide or overcome a plant’s natural defenses.
By shifting toward mixed plantings, where different species are planted in alternating sections or rows, farmers can create “firebreaks” that slow the spread of disease. But because mixed-crop fields can’t be planted and harvested with giant machines, the practice is less economical in the short run and has failed to gain traction with policymakers.
If we can’t bring ourselves to embrace mixed-crop plantings, we’ll need another plan to stave off global famine. Fortunately, there’s a solution that doesn’t require extensive use of agricultural chemicals — but we’ll have to overcome our squeamishness about science.
I’m talking about genetically modified organisms, or GMOs. Although GMOs have been greeted skeptically by health-conscious consumers, many of those consumers fail to realize that not all GMOs are created equal.
The GMOs that rose to infamy in the 1990s were transgenic organisms, created by introducing genes from an entirely different species. Such highly unnatural mutations can have unintended consequences. For instance, scientists found that when genes from Brazil nuts were introduced to improve the nutritional quality of soybeans, the soybeans also took on the Brazil nut’s allergenic properties. For this and other reasons, more than half of the countries in the European Union have banned the cultivation of transgenic crops since 2015.
But recent advances in gene editing technology make it easier than ever to modify plants without introducing genes from other species — say, by snipping out an unwanted gene or by inserting a gene from a different specimen of the same species. Those crops, known as mutagenic organisms, have genomes that are indistinguishable from those that could be developed through conventional selective breeding. Because gene editing can build disease resistance into crops much faster and more accurately than selective breeding can, the technique is better suited to combat the rapid advance of pathogens and insects into new latitudes.
The distinction between transgenic and mutagenic GMOs has largely been lost on the public. Hardly any mention of their differences has come up in the battle over GMO labeling of foods. The lack of nuance was underscored in July when the European Union ruled that mutagenic crops would be subject to the same regulations as transgenic crops under the GMO directive. Sarah Gurr, a food security specialist at the University of Exeter in England, calls the decision a “huge pity.”
The road to mutagenic GMOs was paved largely by CRISPR, an inexpensive technique that Gurr describes as “a stunningly clever way of introducing very small mutations that change the properties of plants.” In China, the world’s largest producer of wheat, CRISPR is already being deployed in the battle against powdery mildew, a fungal disease that afflicts wheat, apples, grapes, and a host of other crops. In 2014, a team led by Caixia Gao in Beijing used CRISPR to knock out multiple copies of a gene that suppresses wheat’s ability to fight off the pathogen.
Since then, Gao and her team have made the CRISPR technology even more efficient. It now takes just two months for them to create and grow a mutagenically modified bread-wheat plant. With conventional selective breeding, the same process could take years — too slow to keep pace with fast-adapting fungi.
Gao’s research could lay the groundwork to defend Chinese wheat producers against a potentially more devastating fungal threat. Wheat blast has been called “one of the most fearsome and intractable wheat diseases in decades” by the International Maize and Wheat Improvement Center. In 2016, it spread from South America to Bangladesh, then into India. If it crosses the Indian border into China, CRISPR may be the world’s best hope for securing the globe’s largest wheat supply.
Given the growing global threats to food security, we cannot afford to throw the baby out with the bathwater. There is an arms race escalating between our crops and the things that destroy them. We need the best possible weapons at our disposal.
To start, that means better educating the public about GMOs. Any initiative to label GMO foods should include distinctions between transgenic and mutagenic GMOs, to fully inform consumers about their choices.
It’s also time to invest in new technologies and solutions to address the climate-related advance of insects and crop diseases. That might mean rethinking our aversion to GMOs. It might also mean bringing an end to monocropping. Either way, bold action is needed. The world’s food supply depends on it.
Anne N. Connor has co-authored two books published by CRC Press, one on ecological sustainability (2013) and one on genomics (2008), including a chapter on ethics. She has recently published on gene editing techniques in The Scientist. She has no conflict of interest with the scientists or research mentioned in this article.