Increased Heat-Drought Combinations Could Damage Crops Globally, Says Study

Sep 22, 2021

Heat and drought events may coincide more often due to climate change, with negative consequences for agriculture, according to a new study. Crop yields often drop during hot growing seasons, and combined heat and drought can magnify the effect, say the authors. The study was just published in the journal Nature Food.

In addition to losses caused by high temperatures alone, the combined effects of heat and drought could cause additional yield decreases in maize and soy of up to 20 percent in parts of the United States, and up to 40 percent in eastern Europe and southeastern Africa, the study says. In places where cool climates currently limit crop yields, such as in the northern United States, Canada and Ukraine, the combined effects of higher temperatures and less water may diminish projected yield gains from warming alone.

Previous projections of future climate risk have identified a danger to crops from global warming, but most have overlooked the potential for compound effects of heat and water availability on food crops, the authors say.

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Based on historical data, yields of maize and soybean are about 40 percent more sensitive to heat in places where heat is accompanied by dry conditions, compared to croplands where hotter weather doesn’t mean less water. This might be because these crops are particularly thirsty under the drying power of hot air, and because dry land cannot cool down as water evaporates; this means soil will get especially hot under the sun’s rays.

The compound impacts of heat and drought were less important for other crops, such as wheat or rice. And warming climate could actually benefit some crops where the coupling between warming and water availability is weak, including in much of Asia, That said, the study shows that without strong and rapid cuts in greenhouse gases, overall supplies of staple foods could be increasingly damaged by compound climate extremes. This raises the risks of higher food prices and reduced food security, even in developed countries.

“Our study uncovers a new risk to crop production from climate warming that we believe is overlooked in current assessments. As the planet continues to warm, water and heat may get more strongly interrelated in many regions, making droughts hotter and heat waves drier,” said lead author Corey Lesk, a researcher at Columbia University’s Lamont-Doherty Earth Observatory. “Plants will increasingly lack water when they need it most, and historically this has been especially damaging for crops.”

Lesk said the the study should serve as a motivation to introduce new crop varieties that can resist the colliding extremes.

The study was coauthored by Radley Horton, also of Lamont-Doherty; Ethan Coffel of Syracuse University; Jonathan Winter of Dartmouth College; Deepak Ray of the University of Minnesota, St. Paul; Jakob Zscheischler of the University of Bern, Switzerland; and Sonia Senevirate of ETH Zurich, Switzerland.

Source : columbia.edu

Video: Can Gene Editing Give Seeds a Stronger Start?

Reagan Reed has a way of describing his research that might make a plant breeder pause.

“I’m the sort of person who likes to break things to understand them,” he says.

What he breaks are genes involved in seed germination. Reed, a Ph.D. candidate at the University of California, Davis, is investigating whether changing those genes can help seeds establish healthy plants under a wider range of conditions.

Reed recently attended the National Association for Plant Breeding meeting in College Station, Texas, as an NAPB Borlaug Scholar. His work speaks to a question that matters well beyond a research lab: what does it take for a seed to get a crop off to a strong start?

A seed that germinates quickly, alongside the others planted with it, spends less time vulnerable to stresses before seedlings become established.

“If you’re able to bridge that gap between germination to stand establishment, then that’s going to give you the highest probability of having a solid yield that year,” Reed says. “There’s a bunch that can go wrong after that, but it maximises your yield from the start, at least.”

Reed works in Dr. Imtiyaz Khanday’s lab at UC Davis, where his research focuses on seed quality in tomatoes and potatoes. He brings an unusual academic background to the work: at Skidmore College, he studied both biology and Latin.

Reed believes that combination prepared him for research. Translating an ancient text means studying each word, weighing its possible meanings and using context to reach the best interpretation. There is rarely a way to know with complete certainty what an author intended. Science, he says, requires a similar willingness to work through uncertainty.

“Attention to detail and comfortability working with uncertainty,” is how he sums up what Latin taught him.

In the lab, uncertainty can produce a surprise. Reed describes changing one gene and seeing little effect. Changing a second gene also appears to do little. Put both changes in the same genetic background, though, and the result can be substantial.

“I break this gene, nothing really happens. I break this other gene, nothing really happens. I combine them into the same genetic background, and now there’s a massive effect,” he says.

Those interactions matter as researchers gain the ability to edit multiple genes at once. They also complicate any simple account of how a trait works: improving a seed may depend on understanding what several genes do together.

For Reed, the question is whether that knowledge could help seeds germinate reliably when conditions are difficult. Some of the genes he studies prevent germination under certain conditions. That response may serve a plant well in one setting while limiting its usefulness in agriculture. He wants to learn what happens when those genes are changed, and whether the result improves establishment.

Yet a discovery that works in a lab still has a long way to travel before it reaches a field. Reed argues that agricultural biotechnology faces an economic challenge as well as a scientific one. New tools can create value for farmers, he says, but developing them requires a way to support the work in an industry where margins can be thin.

His fellowship with Flagship Pioneering gave him a view across AI, agriculture-related work and human health research. It also reinforced the importance of bringing people with different expertise into the same conversation—a benefit of gatherings such as the NAPB meeting.

“You need to have a team of people with different backgrounds who are willing to work together and approach the same problem in different perspectives and different ways,” he says.

That thinking connects the different parts of Reed’s path. Latin taught him to examine details without expecting a perfect answer. Gene editing lets him test what individual genes do—and what happens when their effects combine. Working with people beyond his own field helps him ask what those findings could become.

He came to agriculture because of its reach: the possibility that work by a small group of researchers could eventually make a difference on a much larger scale. His immediate focus is smaller and more precise. He wants to understand what helps a seed get through its first days and become a healthy plant.