Climate crisis could hit yields of key crops even if farmers adapt, study finds. Production of staple crops projected to fall by as much as 120 calories per person per day for every 1C of heating

 

Maize was one of the staple crops covered by the study. Photograph: Maksim Safaniuk/Shutterstock

by  Ajit Niranjan

 

Some of our critical staple crops could suffer “substantial” production losses due to climate breakdown, a study has found, even if farmers adapt to worsening weather.

Maize, soy, rice, wheat, cassava and sorghum yields are projected to fall by as much as 120 calories per person per day for every 1C the planet heats up, according to new research in Nature, with average daily losses that could add up to the equivalent of not having breakfast.

The study found rising incomes and changes in farming practices could stem the losses by about a quarter by 2050 and by one-third by 2100 – though they would not stop them entirely.

 

“In a high-warming future, we’re still seeing caloric productivity losses in the order of 25% at global scale,” said Andrew Hultgren, an environmental economist at the University of Illinois Urbana-Champaign and lead author of the study. “It’s not as bad as a future where adaptation doesn’t happen at all, but it’s not this rosy ‘agriculture is going to benefit from climate change’ kind of picture.”

Farmers are among those hardest-hit by extreme weather events, but scientists have struggled to quantify what climate breakdown will do to food production. A major source of uncertainty is the extent to which farmers will adapt to hotter temperatures by changing which crops they use, when they plant and harvest them, and how they grow them.

The team of researchers from the US and China used data from 12,658 regions in 54 countries to capture the extent to which food producers have adapted to different changes in the climate. They applied these historical relations to models simulating future crop production as temperatures rise and economies grow, and compared the losses with a hypothetical world in which global heating stopped in the early 2000s.

 

In an extreme heating scenario, the study found, the relative yield for a crop such as soy would fall by 26% by 2100, even after accounting for adaptation, rising incomes and the effect of plants growing faster due to extra carbon dioxide in the atmosphere.

A more realistic heating scenario – closer to the level that current policies will cause – would lead to yield losses of 16% for soy, 7.7% for wheat and 8.3% for corn, the study found. Rice was the only one of the six crops the researchers studied whose yields would rise because of climate change, with an expected gain of 4.9%.

The global population is projected to rise from about 8 billion today to 10 billion by the end of the century, increasing demand for food as carbon pollution warps weather patterns. The researchers found the greatest losses would hit modern-day “bread basket” regions with highly productive lands, but added that people in poorer countries would be among the ones least able to afford food.

“In a lot of climate impact studies, the global poor get hurt, and that’s true here too,” said Hultgren. “What is different from a lot of the previous work out there is that relatively rich, well-to-do portions of the world that are bread baskets are actually hit the hardest.”

The research, which uses econometric methods to gauge the total effect of adapting, contrasts with previous studies that explicitly model biophysical interactions. A study in Nature Communications in 2022 using the latter approach found timely adaptation of growing periods would increase actual crop yields by 12%.

 

Jonas Jägermeyr, a researcher at Columbia Climate School and co-author of the study, said the new research did not cover adaptation options that are not implemented today and that its results were likely to be pessimistic.

“Empirical impact studies are known to be overly pessimistic when it comes to far-into-the-future scenarios,” he said. “Process-based models show the importance of plant growth interactions that cannot be empirically trained on historical data.”

But such models have also been criticised for exploring what is theoretically possible without reflecting real-world constraints, such as market failures, human error and the availability of funds.

“The findings [of the new study] are reasonable but represent one end of a legitimate scientific debate,” said Ehsan Eyshi Rezaei, a crop scientist at the Leibniz Centre for Agricultural Landscape Research.

He added: “I view these results as a valuable empirical reality check showing we cannot assume perfect adaptation will save us – even if the truth likely lies between their pessimistic projections and [other researchers’] optimistic ones.”

Soaring Temperatures Threaten Crops, So Scientists Are Looking to Alter the Plants. Genetically altering crops may be key to helping them adapt to extreme temperatures. But shrinking funds and social acceptance stand in the way.

Photosynthesis, the process through which plants get energy, stops working at higher temperatures, which are becoming more common in many of the world’s agricultural regions.Credit...Thomas Lohnes/Getty Images

 

 

By Rebecca Dzombak

 

 

The world’s bread baskets are heating up, threatening the global food supply. Climate change has already shrunk yields for major crops like wheat and maize, and crop losses are likely to worsen in the coming decades.

But researchers are trying to avoid that future by helping plants deal with heat.

“There’s a lot of excitement in identifying why it is that some crops that are grown in the most extreme conditions are able to survive,” said Carl Bernacchi, a crop researcher at the University of Illinois Urbana-Champaign and the author of one of a trio of papers on crop modification that were published Thursday in the journal Science.

Farmers can help crops beat the heat with water-based cooling, but that method has limitations. Modifying crops, either through traditional crossbreeding, artificially sped-up mutation or direct genetic editing, offers control over how plants respond to heat.

Photosynthesis, the process through which plants get energy, grinds to a halt between 40 and 45 degrees Celsius, or 104 to 113 degrees Fahrenheit, temperatures that are becoming more common in many of the world’s agricultural regions.

 

“Photosynthesis really dictates the currency plants have to use,” Dr. Bernacchi said. “If photosynthesis falters, plants run out of energy and die.”

Dr. Bernacchi and his co-authors reviewed the potential of editing rubisco, the key enzyme that transforms carbon into sugar, and its partner, rubisco activase. In plants that grow in warm climates, rubisco activase seems to work better at helping rubisco function. Transferring that molecule from hot-climate plants to cool-climate plants can help cool-climate plants adapt to heat. Simply boosting its activity could help, too.

Altering photosynthesis is still a distant goal, said Walid Sadok, a crop physiologist at the University of Minnesota who was not involved with the paper.

“It’s a complex endeavor,” he said. “It’s still in its infancy, but it’s an interesting idea.”

A plant’s genome can also be altered to change its leaf architecture, spacing leaves out and setting them at just the right angle to ensure a balance of sun and shade that can help maintain temperature and productivity. Editing a leaf’s reflectivity and the amount of chlorophyll, or green pigment, that it contains can help, too.

Plants’ temperature-sensing system could also be modified. In a second Science paper, researchers propose a new way of understanding the network of proteins that control plants’ responses to heat. Instead of plants having discrete “thermometers,” temperature sensing could be spread out in many plant systems and proteins, the researchers say. That could provide many targets for editing for heat tolerance.

 

“We could develop designer crops tailored to future climates,” said Suresh Balasubramanian, a plant geneticist at Monash University in Australia who led the study.

Selective crossbreeding of plants is still a reliable option and should be continued while researchers work toward more complicated genetic editing goals, Dr. Sadok said.

But as temperatures climb beyond levels that modern crops can withstand, genetic editing may be more crucial, Dr. Bernacchi said.

“We may get to a point where existing crops don’t have the genetic diversity we need to adapt crops to the growth conditions that we’re going to see in the near future,” he said. “In that situation, we might need to be creative.”

Wild plants hold a vast pool of genetic diversity that could inspire new ways to keep crops cool. Plants can thrive in the hottest and driest places on Earth, such as Death Valley in California, the Atacama Desert in South America and the Namib Desert in southern Africa, where temperatures regularly soar above the threshold for photosynthesis.

 

Exploring these plants’ genomes could give scientists genes to transfer into staple crops such as soybeans, wheat and rice, bringing along heat tolerance. Scientists can also work backward, starting with a highly heat-tolerant plant and using genetic editing to add other desirable traits, like taste and size.

“We’re trying to cast our net more broadly,” said Sam Yeaman, an evolutionary biologist at the University of Calgary who wrote a third paper. “If we limit ourselves to only looking at crops, we’re going to have a tiny slice of the picture.”

Some complex genetic editing projects, such as photosynthesis or the temperature-sensing system, are years away from hitting farmers’ fields. Other genetic editing tools for heat tolerance, like changes to leaf architecture, could be available sooner, if they could get field tested and permitted, an expensive and time-consuming process.

“Funding right now in the United States doesn’t look particularly promising for the future of this research,” Dr. Bernacchi said.

And acceptance of genetically modified foods has been shrinking over the past decade or so, said Dominique Brossard, who studies the communication of controversial topics at the University of Wisconsin. The Trump administration’s movement toward “natural” foods could further stymie willingness to adopt genetically modified foods, she said.

 

 

(Martianization) - ‘Impossible’ heatwave struck Philippines in April, scientists find Human-caused climate crisis brought soaring temperatures across Asia, from Gaza to Delhi to Manila

 

A man tries to cool himself during hot temperatures in Manila, Philippines, last month. Photograph: Aaron Favila/AP

 

 

 

The record-breaking heatwave that scorched the Philippines in April would have been impossible without the climate crisis, scientists have found. Searing heat above 40C (104F) struck across Asia in April, causing deaths, water shortages, crop losses and widespread school closures.

The extreme heat was made 45 times more likely in India and five times more likely in Israel and Palestine, the study found. The scientists said the high temperatures compounded the already dire humanitarian crisis in Gaza, where displaced people are living in overcrowded shelters with little access to water.

The results of the latest study to assess the role of human-caused global heating in worsening extreme weather shows how severe the impacts are already, with only 1.2C of average heating above preindustrial levels over the past four years.

 

Another “impossible” heatwave hit west Africa and the Sahel in late March, again causing deaths, and reaching 48.5C in Mali. Deaths from extreme heat are poorly recorded in many countries but previous research suggests millions of people have died early over the past two decades. In Europe, where recording is better, heat-related deaths rose by 25% in the past decade.

The scientists warned of worse to come. If global temperature rises to 2C, repeats of April’s extreme heat will be expected every two to three years in the Philippines and every five years in Israel, Palestine and nearby countries. Hundreds of the world’s top climate scientists told the Guardian recently that they expected global inaction in ending fossil fuel burning to result in at least 2.5C of heating.

“From Gaza to Delhi to Manila, people suffered and died when April temperatures soared in Asia,” said Dr Friederike Otto at Imperial College London, part of the World Weather Attribution (WWA) study team. “The additional heat, driven by emissions from oil, gas and coal, is resulting in death for many people.”

Dr Carolina Pereira Marghidan, a heat risk consultant at the Red Cross Red Crescent Climate Centre, said: “The heat really compounded an already dire humanitarian crisis in Gaza, with displaced populations having limited to no access to food, water, healthcare, and generally living in overcrowded shelters which trap heat, or living outdoors.”

 

The WWA research examined three areas that suffered extreme heat in April. Global heating made temperatures 1.7C hotter in Israel, Palestine, Syria, Lebanon and Jordan, and 1C hotter in the Philippines, where 4,000 schools were closed and portable pools set up to help people cool down. The south Asian region examined encompassed India, where the temperature reached 46C, Bangladesh, Myanmar, Laos, Vietnam, Thailand and Cambodia.

“Climate change is an absolute gamechanger when it comes to extreme heat,” said Otto. The study used weather data and climate models to compare the likelihood of heatwaves in today’s hotter climate and in a climate without human-caused heating. The researchers found that the current El Niño climate cycle, which raises global temperatures, had very little effect on the increased likelihood of the heatwaves.

“Asia contains some of the largest and fastest-growing cities in the world,” said Pereira Marghidan. “This rapid urbanisation has in many cases led to unplanned development, increased concrete across the cities, and extreme losses of green space in many cities.” She said outdoor workers such as farmers and street vendors and those in informal housing were particularly vulnerable and that the study showed the need to improve heatwave early warning and planning programmes.

Hundreds of attribution studies have shown how global heating is already supercharging extreme weather across the world. Dr Mariam Zachariah at Imperial College London, who was part of the study team, said: “Unless the world takes massive, unprecedented steps to reduce emissions and keep warming to 1.5C, extreme heat will lead to even greater suffering in Asia.”