FATEHGARH-SAHIB, India — When the unseasonably heavy rains flooded the fields, and then the equally unseasonable heat shriveled the seeds, it didn’t just slash Ranjit Singh’s wheat harvest by nearly half.
It put him, and nearly all the other households in his village in northern India, that much further from financial stability in a country where a majority of people scratch out a living on farms. Like many Indian farmers, Mr. Singh is saddled with enormous debt and wondering how he will repay it, as a warming world makes farming ever more precarious.
For India and other South Asian nations, home to hundreds of millions of humanity’s most vulnerable, a seemingly bottomless well of challenges — poverty, food security, health, governance — has only deepened as the region bakes on the front lines of climate change.
Global warming is no longer a distant prospect that officials with short electoral mandates can choose to look away from. The increasing volatility in weather patterns means a greater risk of disasters and severe economic damage for countries already straining to increase growth and development, and to move past the pandemic’s devastation to lives and livelihoods.
In Pakistan, which is grappling with an economic crisis and a political meltdown, a cholera outbreak in the southwest sent the local government scrambling, just as it was trying to quell massive forest fires.
In Bangladesh, floods that came before the monsoons stranded millions of people, complicating longstanding efforts to improve the country’s response to chronic flooding. In Nepal, officials are trying to drain about-to-burst glacial lakes before they wash away Himalayan villages facing a new phenomenon: too much rain, too little drinking water.
And in India, which is the region’s biggest grain supplier and provides hundreds of millions of its own citizens with food rations, the reduced wheat harvest has resurfaced longstanding concerns about food security and curbed the government’s ambitions to feed the world.
South Asia has always been hot, the monsoons always drenching. And it is far from alone in contending with new weather patterns. But this region, with nearly a quarter of the world’s population, is experiencing such climatic extremes, from untimely heavy rain and floods to scorching temperatures and extended heat waves, that they are increasingly becoming the norm, not the exception.
“We used to wear jackets in March,” said Mr. Singh, the farmer in Punjab, in India’s north. “This year, from the first of March, we were using fans.”
That March was the hottest month in India and Pakistan in 122 years of record-keeping, while rainfall was 60 to 70 percent below the norm, scientists say. The heat came earlier than usual this year, and temperatures stayed up — as high as 49 degrees Celsius, roughly 120 degrees Fahrenheit, in New Delhi in May.
Such a heat wave is 30 times as likely now as before the industrial age, estimates Krishna AchutaRao, a climate researcher at the Indian Institute of Technology. He said that if the globe warms to 2 degrees Celsius above preindustrial temperatures, from the current 1.2 degrees, such extreme patterns will come much more often — perhaps once every 50 years, or even every five.
With the extreme weather, the yield of India’s national wheat harvest was down at least 3.5 percent this year, based on initial information. In Punjab, traditionally India’s wheat basket, the drop was about 15 percent, with some districts seeing as much as a 30 percent decline.
In the Fatehgarh-Sahib area of Punjab, among the worst-hit, farmers like Mr. Singh faced a double calamity. Heavy rains came earlier and lasted longer than usual, inundating the fields. Those who managed to drain the water hoped the worst was over. But in March came the heat wave.
As its intensity became clear, the Indian government suddenly reversed a decision to expand wheat exports, with global supplies already reduced by the war in Ukraine. Officials cited rising international prices and the challenges of food security at home.
Malancha Chakrabarty, a researcher at the Observer Research Foundation in New Delhi who studies climate change and development, said India was “extremely vulnerable” to food security threats not just because of drops in production, but also because much of the population could struggle to afford food as prices rise.
“We are looking at a huge population which is on the borders of being extremely poor,” Dr. Chakrabarty said. Despite significant progress in reducing extreme poverty, she said, many people are merely surviving and “wouldn’t be able to take a shock.”
The damage to the wheat crop has sent yet another tremor through India’s underperforming agriculture sector. In many places, traditional crops are particularly vulnerable to the depletion of groundwater and erratic monsoons. Farmers and the government do not agree on how far to go in opening agriculture markets. Deep in debt, farmers are committing suicide in growing numbers.
The agrarian crisis has pushed many to the cities in search of other work. But India’s economic growth, focused largely at the top, is not expanding employment opportunities. And much of the urban work is outdoor labor, which this year’s extreme heat has made dangerous.
For those still on the farms, global warming is changing the very nature of what they put in the ground.
Agricultural scientists once focused on developing high-yield varieties to meet India’s food needs, after a history of devastating famines. For the past couple of decades, the priority has been increasing crops’ heat resistance. In labs, seeds are being tested at temperatures five degrees Celsius above those outside.
“It is a dilemma,” said Ratan Tiwari, who leads the biotechnology program at the Indian Institute of Wheat and Barley Research in Karnal. “Unless and until you are very sure the heat is going to be there, we will obviously not give a variety that is having heat tolerance but it is not the highest-yielding.”
The institute’s scientists have helped develop about 500 varieties of wheat seeds in the past few decades. What gives Mr. Tiwari and his fellow scientists hope is that overall, the varieties’ tolerance for heat is improving.
“Slowly, the genes are being accumulated in the favorable directions,” he said.
While the drop in the wheat harvest has affected India most directly, the shocks from climate change do not stop at international borders.
Bangladesh and Nepal are reliant on India for wheat imports. Rising tides wreak as much havoc in Bangladesh as in the neighboring Indian regions of Assam and West Bengal. When the water from heavy rains thunders down from the Himalayas, Nepali officials have to try to bring back the endangered rhinoceroses that are swept into India.
The problem with floods in Bangladesh is not new. With hundreds of rivers cutting through the nation of 170 million, rising waters displace hundreds of thousands every year.
The authorities have become better at saving lives through swift evacuations. But they are struggling to predict the timing of floods because of erratic monsoon patterns.
Rayhan Uddin, 35, from the Zakiganj area of Sylhet, Bangladesh, has a tree nursery, farms and about 6.5 acres of paddies. Since 2017, his home, paddy fields and decade-old nursery business have been washed away twice.
“I will have to start the nursery afresh,” he said. “The same happened five years ago.”
Nepal, where a quarter of the population lives below the poverty line, is perhaps the clearest example of how extremes of weather — floods and water shortages on one hand, increasing forest fires on the other — are disrupting life.
Villagers in the Himalayas accustomed to snow are now experiencing heavier rainfall, a phenomenon that is forcing many to migrate. Drinking water is also a major problem, as springs dry up with the reduction in snow melt.
Nepal’s agriculture ministry estimated that about 30 percent of arable land, mainly in hilly areas, was no longer being used. Across the country, forest fires have increased by almost tenfold over the past two decades.
Downstream, agriculture is increasingly uncertain and risky: Last year, paddy production was down nearly 10 percent, with tens of thousands of acres damaged by floods that killed scores of people.
The constant melting of snow due to rising temperatures has increased the number of glacial lakes by the hundreds, with about 20 identified as prone to bursting.
In 2016, the Nepal Army drained Imja Lake near Mount Everest to lower the risk to downstream populations. The authorities are trying to raise money for the immediate draining of four more lakes.
In Pakistan’s restive Baluchistan region, the evidence of an unusual spring was clear for weeks: The sky across several districts turned bright orange as a severe sandstorm blanketed the region. Forest fires on the province’s border burned for weeks, destroying an estimated two million pine and olive trees.
On top of the fires came pestilence. Panic gripped the mountain town of Pir Koh after a large number of people — most of them children — experienced diarrhea, vomiting and leg cramps. By the end of April, officials declared a cholera outbreak, which health officials said could be linked to rising temperatures. More than two dozen people died.
While disease outbreaks, flooding and harvest disasters capture headlines, activists and experts warn about the toll of more constant, routine threats.
“This is everyday climate change at work: a slow-onset shift in environmental conditions that is destroying lives and livelihoods before our eyes,” said a report outlining how tens of thousands of Bangladeshis lose their homes and crops to river erosion every year.
Bhadra Sharma contributed reporting from Kathmandu, Nepal, Saif Hasnat from Dhaka, Bangladesh, Zia ur-Rehman from Karachi, Pakistan, and Suhasini Raj from New Delhi.