Rice has historically been a heat-loving plant. In fact, the wild ancestor of cultivated rice once grew primarily on the sweltering, rain-swept Malay and Indochina peninsulas as well as the islands of Southeast Asia. It wasn’t until Earth’s climate warmed after the last ice age that wild rice substantially spread into central China and South Asia, where it was independently domesticated by humans in two events that arguably rank among the most important in the history of our species.
Rice fueled many of the earliest civilizations and remains a virtually indispensable source of food in the modern world. Today, half of all humans get 20% of their calories from rice, and more than a billion people are reliant on the production and distribution of rice for their livelihoods.
That might be about to change. Scientists warn that over the next 50 years, global warming caused by the emission of greenhouse gases will accelerate to a pace that is 5,000 times faster than rice, and many other crop species, have ever had to contend with at any time during their evolutionary history.
Left to its own devices, even rice — with its proclivity for heat — would almost certainly be unable to keep up. With the help of humans, who carefully breed and genetically engineer new varieties, it’s possible rice will be able to cope. But, said Nicolas Gauthier , curator of artificial intelligence at the Florida Museum of Natural History, the best-case scenario is not something anyone’s looking forward to.
“These changes are going to be disruptive, and the process of adaptation doesn’t come for free. It has to be done with intention and might not be pleasant,” he said.
Gauthier is the lead author of a new study that combines data from multiple scientific disciplines to predict the possible future for rice — or lack thereof — in a rapidly warming world. The prognosis is grim.
“Regions in the south, such as Indonesia and Malaysia, are the ones that are going to be most heavily impacted, and the process of adapting is going to leave a lot of people out of the loop. Those who depend on rice for their subsistence today aren’t necessarily the ones who are going to be able to access the new genetic varieties that are developed.”
The threat to food security posed by global warming is multifaceted, and in the case of rice, it involves a long history of adaptation in the opposite thermal direction toward cooler climates.
Rice was initially domesticated in the Yangtze River basin in central China between 7,000 and 9,000 years ago, when balmy temperatures and frequent rain made it possible for humans to develop agricultural societies around the world. Trade networks connected these societies like hyphae, and early rice cultivars were among the many goods that streamed along them.
Based on archaeological evidence, rice farms in China expanded to the north and east along the course of the Huang He River and westward into interior China beginning roughly 5,000 years ago and continuing for a millennium. Then, about 4,200 years ago, a period of abrupt cooling and drought struck much of Eurasia, causing several civilizations — including the Akkadian Empire and the Egyptian Old Kingdom — to wane.
Rice farmers in China adapted by cultivating new varieties of rice that could tolerate colder temperatures. The existence of these new cold-tolerant varieties eventually allowed rice production to spread to regions with more temperate climates, such as Korea and Japan.
In contrast, transitioning from cold to hot climates can involve more than just a plant expediting its developmental timeline.
“You don’t see that kind of flexibility on the hot end because at some point, the plant will physically stop working,” Gauthier said.
By way of analogy, if you were to move into a house north of the Arctic Circle, you might compensate for the longer winters by staying inside for a greater portion of the year and staying outdoors as long as possible during the 20-hour halcyon days of summer. But if you move to a place where summers get too hot, you might suffer from heat stroke. Spending the summer indoors might be an option for you, but rice gets all its nutrition from being out in the sun and doesn’t have that luxury.
Gauthier wanted to know the upper temperature threshold beyond which modern rice varieties are unable to extend. Working with colleagues from New York University and the University of Washington, Gauthier combined archaeological and botanical records, including satellite imagery, agricultural records and herbarium data, to figure out where rice was grown historically and where it grows now.
This resulted in a map to which they could add current, historical and future climate projections. Using this, they determined that rice today is grown almost entirely in areas with a mean annual temperature of less than 82° degrees Fahrenheit and an average monthly maximum of less than 104 F . This aligns well with data from other studies that demonstrate rice begins showing signs of heat stress at anything above 91 F .
With this baseline in hand, the authors used artifacts from 803 archaeological sites to trace the historical movement of rice and determine how that coincided with past temperatures. The results indicate that at no point during its 9,000 years of cultivation has rice ever been grown in a region with a mean annual temperature of more than 82 F . There were a few archaeological sites in northern India and Pakistan in which the average monthly maximum temperature exceeded 104 F , but given the arid climate of these regions, the authors note that long-distance trade may be a more plausible explanation for how rice ended up at those locations rather than it having been grown there.
Thus, 104 F seems to be the cutoff, and anything with an annual average above 82 F is pushing it.
Finally, the authors projected future global temperatures using climate models to see where rice might have a chance of growing over the next century. By 2070, the results suggest that almost the entire southern distribution of rice, from India through Malaysia, will have mean annual temperatures of more than 82 F . A maximum monthly average temperature of more than 104 F during the hottest months of the year is expected for most of India, as well as parts of China and the Middle East.
India became the world’s top rice-producing country, a title previously held by China, after growing nearly 150 million metric tons of rice grain. Were anything to suddenly and negatively affect India’s ability to grow rice, ensuing mass starvation is a very real possibility.
Under business-as-usual models of climate change, in which countries are collectively unable to significantly reduce the emission of fossil fuels, rice growers and consumers have about 50 years to prepare for the worst. Much of that preparation and adaptation will probably involve growing tropical varieties of rice in what are today more temperate regions and growing temperate varieties at higher latitudes than they are currently able to grow. But even if this averts famine, Gauthier warned, the process will still be unutterably difficult and its effects distributed unequally.
“On an aggregate scale, it could be that, pound for pound, all the rice that won’t be able to grow in Southeast Asia could be grown in China instead, but that doesn’t change the impact on the people in Southeast Asia who can’t just start growing a new crop from scratch.”
Additional co-authors of the study are Ornob Alam and Michael Purugganan of New York University and Jade d’Alpoim Guedes of the University of Washington.
Communications Earth & Environment
Projected warming will exceed the long-term thermal limits of rice cultivation
14-Jan-2026