Feeds:
Posts
Comments

Archive for the ‘Climate change’ Category

Washington Post

A recipe for fighting climate change and feeding the world

A ladybug rests on a Kernza seed head in one of Sustain-a-Grain's farm fields. The ladybug indicates a healthy and diverse ecosystem. (Chase Castor for The Washington Post)
A ladybug rests on a Kernza seed head in one of Sustain-a-Grain’s farm fields. The ladybug indicates a healthy and diverse ecosystem. (Chase Castor for The Washington Post)

Scientists hope this new kind of perennial
grain offers a taste of what environmentally
friendly farming could look like

By Sarah KaplanUpdated Oct. 12 at 9:01 a.m.Originally published Oct. 12, 2021369

“It’s so different from anything I’ve baked with,” says my baking partner, Jenny Starrs.

We’re standing in the tiny kitchen of my D.C. apartment, examining palmfuls of a dark, coarse, rich-scented flour. It’s unfamiliar because it was milled from Kernza, a grain that is fundamentally unlike all other wheat humans grow.Story continues below advertisement

Most commercial crops are annual. They provide only one harvest and must be replanted every year. Growing these foods on an industrial scale usually takes huge amounts of water, fertilizer and energy, making agriculture a major source of carbon and other pollutants. Scientists say this style of farming has imperiled Earth’s soils, destroyed vital habitats and contributed to the dangerous warming of our world.

But Kernza — a domesticated form of wheatgrass developed by scientists at the nonprofit Land Institute — is perennial. A single seed will grow into a plant that provides grain year after year after year. It forms deep roots that store carbon in the soil and prevent erosion. It can be planted alongside other crops to reduce the need for fertilizer and provide habitat for wildlife.

In short, proponents say, it can mimic the way a natural ecosystem works — potentially transforming farming from a cause of environmental degradation into a solution to the planet’s biggest crises.

[Try the recipe: Kernza sourdough]

This summer I traveled to Kansas, where I met the scientists who are trying to make Kernza as hardy and fertile as traditional wheat. I visited the farmers who must figure out how to grow it effectively. And I invited my friend Jenny, the founder of artisan baking company Starrs Sourdough, to help me make a loaf of Kernza bread.

Kernza has a long road from the laboratory to the kitchen table. It will be even harder to transform the farming practices that humans have relied on for most of history. But if the scientists, farmers and processors are successful, perennial foods might one day be available on grocery store shelves — and the bread that Jenny and I are baking could offer a taste of what’s to come.

The soil

The first step in Jenny’s bread recipe is making the “levain” — a mix of flour, water and yeast that ferments for a long time, producing lots of air bubbles and tasty lactic acid.

While the microbes chow down, Jenny and I compare the whole Kernza to some wheat kernels she has on hand. The Kernza grains are smaller, and they contain less of the gluten protein that makes traditional wheat good for baking bread.

“Obviously, bread flour is awesome,” Jenny says — after all, humans have been perfecting it for nearly 10,000 years.

At the end of the last ice age, in the fertile river valleys of the Middle East, China and Mexico, people found they could sustain themselves more easily by cultivating crops. Three annual grasses — wheat, rice and corn — became the foundation of human diets and human civilization.

[What questions do you have about climate change or extreme weather? Ask The Post.]

Freed from the need to rove the landscape in search of food, people settled down and constructed cities. Religions and school calendars were structured around the rhythms of farming: planting seeds, helping them grow, harvesting grains and then tilling the soil to prepare it for the next round of planting. Generations of careful breeding improved crops’ taste and yield, and ever- stronger fertilizers have made farms still more productive. The population boomed.

But the planet has paid the price. The practice of tillage — churning the ground to destroy weeds and facilitate the planting of next year’s crop — has depleted the very earth from which our food is grown. It breaks up clumps of organic matter and exposes them to the sunlight, releasing carbon into the atmosphere. Tilled soil is less able to hold water, causing nutrients and other particles to run off into rivers, lakes and the sea.

Research suggests that the world’s soils are now eroding 100 times faster than new soil can form, and an estimated 33 percent of soil is so degraded that its ability to grow crops is compromised. Meanwhile, monoculture — the strategy of sowing huge fields with a single crop — achieves higher yields but also puts more pressure on soil and increases the risk that plants will succumb to pests or disease.

Many of humanity’s solutions to these problems also create other issues, Land Institute researchers say. Fertilizer can counter soil degradation, but it pollutes waterways and produces nitrous oxide, a potent greenhouse gas. Pesticides might reduce threats from insects, but they destroy other vital species. Cover crops will curb erosion, but they can be difficult to plant and maintain.

And modern farming is hugely carbon intensive. Factoring in fuel for machinery and food transport, methane produced by belching livestock, and the carbon that’s lost when ecosystems are converted to cropland, agriculture accounts for about a quarter of humanity’s annual planet-warming emissions.

Yet farms are also threatened by climate change, which will increase the risk of prolonged droughts and catastrophic floods.Story continues below advertisement

In Kansas, one of the nation’s leading producers of wheat, these problems are on full display. The state loses an estimated 190 million tons of its rich topsoil each year. Climate change has made Kansas summers hotter and drier, but also makes rainstorms more intense. The state’s farmers are among those most at risk of losing crops as a consequence of human-caused warming.

“It’s a disaster,” Tim Crews, the Land Institute’s lead soil ecologist, tells me one damp day in June. Our shoes squelch in the mud as he leads me around the institute’s Salina, Kan., campus. As we talk, the rain is almost certainly destabilizing soil and washing it into surrounding streams.

Crews sweeps his hand out, as if to indicate not only the farm fields across the road but the entire U.S. agricultural system.

“This is the ecosystem that feeds us, and it has just been nuked,” Crews says. “Is this really the best we can do?”

The seed

Land Institute scientists disagree about how to describe what they’re proposing. Is it a natural evolution from the past 10,000 years of annual agriculture? Or something more like a midcourse correction?

Rachel Stroer, the Land Institute’s president, calls it a “paradigm shift.”

“Instead of an annual monoculture,” she says, “we’re trying to create a perennial polyculture” — cultivating diverse mixes of long-lived plants.

“We want to create an agricultural system to feed humanity that uses nature as the measure of success.”

[Pets can help fight climate change with an insect-based diet. Owners just need to come around to the idea.]

Before people started intensively farming here, Kansas boasted some of the richest soils on Earth. In native prairies, dozens of grass species intermingled with clover, wildflowers, lichens and shrubs, their roots extending as far as 15 feet into the ground. Periodic fires sparked by lightning or set by native people helped clear debris and promote new growth. Insects, birds, prairie dogs and buffalo foraged in the vegetation, while millions of munching microbes buried carbon and other nutrients deep in the earth.

“The ecosystems that built the soils upon which we eat today, and that we have degraded, were perennial and diverse,” Stroer says. “That’s where we get those two characteristics that we’re trying to bring back into agriculture.”

Yet proponents of perennial polyculture have a problem: More than half of all calories consumed by people come from grains, and no one has ever domesticated a grain that lived beyond a year.

That challenge falls to plant biologists such as Lee DeHaan. The son of a Minnesota corn and soy grower, he’d heard family members talk about the Land Institute’s ideas with some skepticism.

“But it captivated me,” he says. “I saw it as solving food for humans, environmental problems and financial security for farmers.”

He began experimenting with a wild grain known as Thinopyrum intermedium, or intermediate wheatgrass. Originally from the steppes of Europe and Asia, it had been brought to North America as forage for cattle, but scientists had a hunch it could also feed people.

In the early 2000s, Land Institute scientists planted their first plots of intermediate wheatgrass. When the plants matured, DeHaan and his colleagues selected the 1,000 top specimens to replant. And when those plants matured, they chose the best among them for further breeding. It was the same process that farmers have been using to domesticate crops for millennia.

To the scientists’ surprise, those early harvests were wildly successful. The new batch of plants had stronger stalks and bigger seeds that didn’t fall out of their husks before they could be harvested.

[Desalination can make saltwater drinkable — but it won’t solve the U.S. water crisis]

“We started to realize we were not that far away from something farmers could actually use,” DeHaan says.

“But the original domestication of crops took hundreds and thousands of years,” he adds. “And with climate change, we don’t have that much time.”

So he turned to tools that were unavailable to his ancient predecessors: gene sequencing, artificial intelligence and advanced supercomputers. Once DeHaan identified the genetic markers associated with the traits he was looking for, he didn’t need to wait for the plants to fully mature before picking the best ones to breed.

After two decades and 11 cycles of this process, the Land Institute has domesticated a form of wheatgrass whose seeds are two to three times bigger than those of its wild ancestor. Under ideal conditions, it can provide as much as 30 percent of the yield of traditional wheat. They call their trademarked creation Kernza — an amalgamation of “kernel” and “Kansas.”Story continues below advertisement

But the plant’s best qualities are below ground. DeHaan shows me a photograph of Kernza’s roots hanging in a Land Institute stairwell — the life-size image is so long, it takes up two stories. In the first four years after planting, Land Institute research suggests, a one-acre plot of Kernza will pull roughly 6.5 tons of carbon dioxide out of the air and into those deep roots.

Kernza can’t completely replace regular wheat — at least, not yet. As Jenny kneads our bread dough, she explains that the weaker gluten proteins in Kernza flour make it harder for loaves to hold their shape. And because Kernza grains are so small, the flour also has proportionally more bran, the hard outer coating of a grain. This isn’t necessarily a bad thing — bran is full of fiber, protein and other nutrients. But it’s not exactly ideal for making angel food cake.

Still, mixed with an equal amount of whole-wheat bread flour, it’s shaping up to make a good-looking loaf. Jenny places the dough inside a cast-iron cooking pot, which will help the bread bake evenly, and slides it into the hot, waiting oven.

The harvest

Before those grains arrived in my kitchen, they were grown by someone like Brandon Kaufman, a fourth-generation Kansas farmer. Kaufman is one of the co-founders of Sustain-a-Grain, a coalition of growers and buyers working to turn the Land Institute’s vision of perennial polyculture into a marketable reality.

That means more than just planting Kernza. Farmers must also figure out how to cultivate it alongside other species, creating fields that are diverse as well as deep-rooted.

[A new report measures the true cost of the American diet]

I visit Kaufman on a sparkling summer morning, driving past endless rows of corn, soy and wheat that blanket central Kansas. The orderly fields belie the tumult facing many small farmers. Net cash income for farms in McPherson County, where Kaufman lives, fell by half between 2012 and 2017, according to the U.S. Department of Agriculture. Buying seeds, fertilizer and equipment can put farmers in the red before a single grain is harvested, and natural disasters — which are growing worse because of climate change — can wipe out a whole year’s work in a single day. The combined debt of all U.S. farmers totals more than $400 billion.

Compared with more-traditional farms, Kaufman’s plots look somewhat scruffy. Tufts of chicory, alfalfa and clover are interspersed with the tall stands of Kernza. Ladybugs dot the greenery, and songbirds twitter in the brush. Kaufman leans down to turn over a dried clump of dung — an offering from the cattle he brings to graze here twice a year. Wriggling in the exposed dirt are several soil-enriching earthworms.Story continues below advertisement

Kaufman’s neighbors would call his fields “dirty.” The mix of crops makes them harder to harvest by machine and less profitable per square foot. His own father, who gave him this land, is skeptical of the whole experiment.

Yet Kaufman says perennial polyculture has been profitable for him. He points out the rich, dark green color of Kernza growing beside patches of alfalfa — a product of the latter plant’s ability to fix nitrogen in the soil. When he brings his cattle to eat the alfalfa, they will spread their waste across the fields and trammel old vegetation into the earth. All this means Kaufman doesn’t have to buy synthetic fertilizers or spend time hauling manure. The ladybugs and birds feed on crop pests, reducing the need for pesticides.

“I don’t need all these inputs and overhead,” Kaufman says. “Diversity is my crop insurance.”

[Why we shouldn’t give in to climate despair]

That’s not to say it’s easy. Kaufman is in a constant battle with weeds, which flourish in his herbicide-free fields. Farm equipment isn’t designed to handle Kernza’s small grains, so harvesting and processing are less efficient. There are scores of kinks to work out in the supply chain connecting farmers to consumers.

But Kaufman thinks about the land he inherited, depleted by a century of intensive farming. He thinks about the state of the planet, battered by climate change and species loss and habitat destruction.

And he thinks about his four children, who he hopes will someday earn their livings from this earth. If his experiments with Kernza are successful, he’ll be able to leave them not just a healthier farm but a healthier world.

“Talk about a legacy,” he says.

The meal

Two decades after the Land Institute planted its first field of intermediate wheatgrass, Kernza can be found in the ingredient lists of cereals, baked goods and beers. For now, most of the products are pricey — the flour that Jenny and I are baking with costs more than $11 per pound, for example, compared with less than $1 per pound for regular all-purpose flour.

Meanwhile, DeHaan and colleagues around the world are working on perennializing other crops: soybeans, sorghum, sunflowers for oil. A form of perennial rice developed at Yunnan University in China has been in commercial production since 2018.

“There’s a lot more belief we can achieve what once seemed unachievable,” DeHaan said.Story continues below advertisement

The proof will be in the eating. Jenny pulls our loaf from the oven, filling the kitchen with a tantalizing, yeasty smell.

“I’m excited that there’s movement in the idea of more sustainable agriculture,” she says. “I hope this can prove there’s a market.”

Finally the bread is cool enough to cut into. Jenny takes a bite, tilts her head and chews. “It tastes like —” she trails off, then tries again.

“Texturally, it’s like rye, but a little spongier,” she says. “And it’s almost like it’s got a hint of herby or spicy-ness.”

She grins. “It’s delicious.”

And we both grab another slice.

About this story

Photo editing by Olivier Laurent. Design and development by Andrew Braford.Sarah KaplanFollowSarah Kaplan is a climate reporter covering humanity’s response to a warming world. She previously reported on Earth science and the universe.

Read Full Post »

INDEPENDENT JOURNALISM SINCE 1921

  • Science News

Rice feeds half the world. Climate change’s droughts and floods put it at risk

Scientists and growers will need to innovate to save the staple crop

an aerial photo of rice fields
In a severe drought, rice farmers in California’s Sacramento Valley have to leave some of their fields unplanted (upper left).CALIFORNIA RICE COMMISSION, BRIAN BAER

Share this:

By Nikk Ogasa

SEPTEMBER 24, 2021 AT 6:00 AM

Under a midday summer sun in California’s Sacramento Valley, rice farmer Peter Rystrom walks across a dusty, barren plot of land, parched soil crunching beneath each step.

In a typical year, he’d be sloshing through inches of water amid lush, green rice plants. But today the soil lies naked and baking in the 35˚ Celsius (95˚ Fahrenheit) heat during a devastating drought that has hit most of the western United States. The drought started in early 2020, and conditions have become progressively drier.

Low water levels in reservoirs and rivers have forced farmers like Rystrom, whose family has been growing rice on this land for four generations, to slash their water use.

Rystrom stops and looks around. “We’ve had to cut back between 25 and 50 percent.” He’s relatively lucky. In some parts of the Sacramento Valley, depending on water rights, he says, farmers received no water this season.

California is the second-largest U.S. producer of rice, after Arkansas, and over 95 percent of California’s rice is grown within about 160 kilometers of Sacramento. To the city’s east rise the peaks of the Sierra Nevada, which means “snowy mountains” in Spanish. Rice growers in the valley below count on the range to live up to its name each winter. In spring, melting snowpack flows into rivers and reservoirs, and then through an intricate network of canals and drainages to rice fields that farmers irrigate in a shallow inundation from April or May to September or October.

If too little snow falls in those mountains, farmers like Rystrom are forced to leave fields unplanted. On April 1 this year, the date when California’s snowpack is usually at its deepest, it held about 40 percent less water than average, according to the California Department of Water Resources. On August 4, Lake Oroville, which supplies Rystrom and other local rice farmers with irrigation water, was at its lowest level on record.

a barren muddy field
Drought in the Sacramento Valley has forced Peter Rystrom and other rice farmers to leave swaths of land barren.N. OGASA

Not too long ago, the opposite — too much rain — stopped Rystrom and others from planting. “In 2017 and 2019, we were leaving ground out because of flood. We couldn’t plant,” he says. Tractors couldn’t move through the muddy, clay-rich soil to prepare the fields for seeding.

Climate change is expected to worsen the state’s extreme swings in precipitation, researchers reported in 2018 in Nature Climate Change. This “climate whiplash” looms over Rystrom and the other 2,500 or so rice producers in the Golden State. “They’re talking about less and less snowpack, and more concentrated bursts of rain,” Rystrom says. “It’s really concerning.”

Farmers in China, India, Bangladesh, Indonesia, Vietnam — the biggest rice-growing countries — as well as in Nigeria, Africa’s largest rice producer — also worry about the damage climate change will do to rice production. More than 3.5 billion people get 20 percent or more of their calories from the fluffy grains. And demand is increasing in Asia, Latin America and especially in Africa.

To save and even boost production, rice growers, engineers and researchers have turned to water-saving irrigation routines and rice gene banks that store hundreds of thousands of varieties ready to be distributed or bred into new, climate-resilient forms. With climate change accelerating, and researchers raising the alarm about related threats, such as arsenic contamination and bacterial diseases, the demand for innovation grows.

“If we lose our rice crop, we’re not going to be eating,” says plant geneticist Pamela Ronald of the University of California, Davis. Climate change is already threatening rice-growing regions around the world, says Ronald, who identifies genes in rice that help the plant withstand disease and floods. “This is not a future problem. This is happening now.”

The top rice producers are in Asia

The world’s top rice producer is China, at 214 million metric tons. India, Bangladesh, Indonesia and Vietnam are next. In Africa, Nigeria (6.8 million) is the largest producer. Brazil (11.8 million) and the United States (10.2 million) are also top producers, according to 2018 data from the U.N. Food and Agriculture Organization.

Worldwide rice production, 2018
a map showing where rice is grown around the world
OURWORLDINDATA.ORG

SOURCE: FAO

Saltwater woes

Most rice plants are grown in fields, or paddies, that are typically filled with around 10 centimeters of water. This constant, shallow inundation helps stave off weeds and pests. But if water levels suddenly get too high, such as during a flash flood, the rice plants can die.

Striking the right balance between too much and too little water can be a struggle for many rice farmers, especially in Asia, where over 90 percent of the world’s rice is produced. Large river deltas in South and Southeast Asia, such as the Mekong River Delta in Vietnam, offer flat, fertile land that is ideal for farming rice. But these low-lying areas are sensitive to swings in the water cycle. And because deltas sit on the coast, drought brings another threat: salt.

Salt’s impact is glaringly apparent in the Mekong River Delta. When the river runs low, saltwater from the South China Sea encroaches upstream into the delta, where it can creep into the soils and irrigation canals of the delta’s rice fields.

a farmer's hand holding dead rice plants being pulled from a paddy
In Vietnam’s Mekong River Delta, farmers pull dead rice plants from a paddy that was contaminated by saltwater intrusion from the South China Sea, which can happen during a drought.HOANG DINH NAM/AFP VIA GETTY IMAGES

“If you irrigate rice with water that’s too salty, especially at certain [growing] stages, you are at risk of losing 100 percent of the crop,” says Bjoern Sander, a climate change specialist at the International Rice Research Institute, or IRRI, who is based in Vietnam.

In a 2015 and 2016 drought, saltwater reached up to 90 kilometers inland, destroying 405,000 hectares of rice paddies. In 2019 and 2020, drought and saltwater intrusion returned, damaging 58,000 hectares of rice. With regional temperatures on the rise, these conditions in Southeast Asia are expected to intensify and become more widespread, according to a 2020 report by the Economic and Social Commission for Asia and the Pacific.

Then comes the whiplash: Each year from around April to October, the summer monsoon turns on the faucet over swaths of South and Southeast Asia. About 80 percent of South Asia’s rainfall is dumped during this season and can cause destructive flash floods.

Bangladesh is one of the most flood-prone rice producers in the region, as it sits at the mouths of the Ganges, Brahmaputra and Meghna rivers. In June 2020, monsoon rains flooded about 37 percent of the country, damaging about 83,000 hectares of rice fields, according to Bangladesh’s Ministry of Agriculture. And the future holds little relief; South Asia’s monsoon rainfall is expected to intensify with climate change, researchers reported June 4 in Science Advances.

A hot mess

Water highs and lows aren’t the entire story. Rice generally grows best in places with hot days and cooler nights. But in many rice-growing regions, temperatures are getting too hot. Rice plants become most vulnerable to heat stress during the middle phase of their growth, before they begin building up the meat in their grains. Extreme heat, above 35˚ C, can diminish grain counts in just weeks, or even days. In April in Bangladesh, two consecutive days of 36˚ C destroyed thousands of hectares of rice.

In South and Southeast Asia, such extreme heat events are expected to become common with climate change, researchers reported in July in Earth’s Future. And there are other, less obvious, consequences for rice in a warming world.

One of the greatest threats is bacterial blight, a fatal plant disease caused by the bacterium Xanthomonas oryzae pv. oryzae. The disease, most prevalent in Southeast Asia and rising in Africa, has been reported to have cut rice yields by up to 70 percent in a single season.

“We know that with higher temperature, the disease becomes worse,” says Jan Leach, a plant pathologist at Colorado State University in Fort Collins. Most of the genes that help rice combat bacterial blight seem to become less effective when temperatures rise, she explains.

And as the world warms, new frontiers may open for rice pathogens. An August study in Nature Climate Change suggests that as global temperatures rise, rice plants (and many other crops) at northern latitudes, such as those in China and the United States, will be at higher risk of pathogen infection.

Meanwhile, rising temperatures may bring a double-edged arsenic problem. In a 2019 study in Nature Communications, E. Marie Muehe, a biogeochemist at the Helmholtz Centre for Environmental Research in Leipzig, Germany, who was then at Stanford University, showed that under future climate conditions, more arsenic will infiltrate rice plants. High arsenic levels boost the health risk of eating the rice and impair plant growth.

Leaching in

When grown in a greenhouse at 5 degrees Celsius above preindustrial temperatures with elevated carbon dioxide levels (representing a future climate), California rice varieties absorbed more of a type of highly toxic arsenic from the soil, raising the rice’s arsenic levels above European Union safety thresholds.

Arsenic levels in rice grains
a chart showing arsenic in rice under different climate conditions
CREDIT: E. OTWELL

SOURCE: E.M. MUEHE ET AL/NATURE COMM.2019

Arsenic naturally occurs in soils, though in most regions the toxic element is present at very low levels. Rice, however, is particularly susceptible to arsenic contamination, because it is grown in flooded conditions. Paddy soils lack oxygen, and the microbes that thrive in this anoxic environment liberate arsenic from the soil. Once the arsenic is in the water, rice plants can draw it in through their roots. From there, the element is distributed throughout the plants’ tissues and grains.

Muehe and her team grew a Californian variety of rice in a local low-arsenic soil inside climate-controlled greenhouses. Increasing the temperature and carbon dioxide levels to match future climate scenarios enhanced the activity of the microbes living in the rice paddy soils and increased the amount of arsenic in the grains, Muehe says. And importantly, rice yields diminished. In the low-arsenic Californian soil under future climate conditions, rice yield dropped 16 percent.

According to the researchers, models that forecast the future production of rice don’t account for the impact of arsenic on harvest yields. What that means, Muehe says, is that current projections are overestimating how much rice will be produced in the future.

Managing rice’s thirst

From atop an embankment that edges one of his fields, Rystrom watches water gush from a pipe, flooding a paddy packed with rice plants. “On a year like this, we decided to pump,” he says.

Able to tap into groundwater, Rystrom left only about 10 percent of his fields unplanted this growing season. “If everybody was pumping from the ground to farm rice every year,” he admits, it would be unsustainable.

One widely studied, drought-friendly method is “alternate wetting and drying,” or intermittent flooding, which involves flooding and draining rice paddies on one- to 10-day cycles, as opposed to maintaining a constant inundation. This practice can cut water use by up to 38 percent without sacrificing yields. It also stabilizes the soil for harvesting and lowers arsenic levels in rice by bringing more oxygen into the soils, disrupting the arsenic-releasing microbes. If tuned just right, it may even slightly improve crop yields.

But the water-saving benefits of this method are greatest when it is used on highly permeable soils, such as those in Arkansas and other parts of the U.S. South, which normally require lots of water to keep flooded, says Bruce Linquist, a rice specialist at the University of California Cooperative Extension. The Sacramento Valley’s clay-rich soils don’t drain well, so the water savings where Rystrom farms are minimal; he doesn’t use the method.

Building embankments, canal systems and reservoirs can also help farmers dampen the volatility of the water cycle. But for some, the solution to rice’s climate-related problems lies in enhancing the plant itself.

three men stand next to each other
Fourth-generation rice farmer Peter Rystrom (left) stands with his grandfather Don Rystrom (middle) and his father Steve Rystrom (right).CALIFORNIA RICE COMMISSION, BRIAN BAER

Better breeds

The world’s largest collection of rice is stored near the southern rim of Laguna de Bay in the Philippines, in the city of Los Baños. There, the International Rice Genebank, managed by IRRI, holds over 132,000 varieties of rice seeds from farms around the globe.

Upon arrival in Los Baños, those seeds are dried and processed, placed in paper bags and moved into two storage facilities — one cooled to 2˚ to 4˚ C from which seeds can be readily withdrawn, and another chilled to –20˚ C for long-term storage. To be extra safe, backup seeds are kept at the National Center for Genetic Resources Preservation in Fort Collins, Colo., and the Svalbard Global Seed Vault tucked inside a mountain in Norway.

All this is done to protect the biodiversity of rice and amass a trove of genetic material that can be used to breed future generations of rice. Farmers no longer use many of the stored varieties, instead opting for new higher-yield or sturdier breeds. Nevertheless, solutions to climate-related problems may be hidden in the DNA of those older strains. “Scientists are always looking through that collection to see if genes can be discovered that aren’t being used right now,” says Ronald, of UC Davis. “That’s how Sub1 was discovered.”

two people in blue jumpsuits looking at rice seeds on shelves
Over 132,000 varieties of rice seeds fill the shelves of the climate-controlled International Rice Genebank. Breeders from around the world can use the seeds to develop new climate-resilient rice strains.IRRI/FLICKR (CC BY-NC-SA 2.0)

The Sub1 gene enables rice plants to endure prolonged periods completely submerged underwater. It was discovered in 1996 in a traditional variety of rice grown in the Indian state of Orissa, and through breeding has been incorporated into varieties cultivated in flood-prone regions of South and Southeast Asia. Sub1-wielding varieties, called “scuba rice,” can survive for over two weeks entirely submerged, a boon for farmers whose fields are vulnerable to flash floods.

Some researchers are looking beyond the genetic variability preserved in rice gene banks, searching instead for useful genes from other species, including plants and bacteria. But inserting genes from one species into another, or genetic modification, remains controversial. The most famous example of genetically modified rice is Golden Rice, which was intended as a partial solution to childhood malnutrition. Golden Rice grains are enriched in beta-carotene, a precursor to vitamin A. To create the rice, researchers spliced a gene from a daffodil and another from a bacterium into an Asian variety of rice.

Three decades have passed since its initial development, and only a handful of countries have deemed Golden Rice safe for consumption. On July 23, the Philippines became the first country to approve the commercial production of Golden Rice. Abdelbagi Ismail, principal scientist at IRRI, blames the slow acceptance on public perception and commercial interests opposed to genetically modified organisms, or GMOs (SN: 2/6/16, p. 22).

Looking ahead, it will be crucial for countries to embrace GM rice, Ismail says. Developing nations, particularly those in Africa that are becoming more dependent on the crop, would benefit greatly from the technology, which could produce new varieties faster than breeding and may allow researchers to incorporate traits into rice plants that conventional breeding cannot. If Golden Rice were to gain worldwide acceptance, it could open the door for new genetically modified climate- and disease-resilient varieties, Ismail says. “It will take time,” he says. “But it will happen.”

Climate change is a many-headed beast, and each rice-growing region will face its own particular set of problems. Solving those problems will require collaboration between local farmers, government officials and the international community of researchers.

“I want my kids to be able to have a shot at this,” Rystrom says. “You have to do a lot more than just farm rice. You have to think generations ahead.”

Climate-resilient rice

To keep rice bowls around the world full, researchers breed new varieties of rice that can endure stresses like drought, floods and salt.

Sahbhagi Dhan: Traditional rice varieties take 120 to 150 days to harvest and require four irrigations. Sahbhagi Dhan is a drought-tolerant variety harvested after 105 days and just two irrigations. In normal conditions, it produces about twice as much rice (four to five metric tons per hectare) as other local varieties in India. Under drought conditions, it produces one to two metric tons per hectare; local varieties produce none.

rice paddies
Scuba rice contains a gene that enables the plant to survive several days underwater, important for areas that experience flooding.IRRI/FLICKR (CC BY-NC-SA 2.0)

Scuba riceSub1, a submergence-tolerance gene, has been bred into scuba rice varieties. Rice normally dies after three to four days of total submergence — many varieties will exhaust themselves to death trying to quickly grow to the water’s surface. Sub1 varieties (shown), however, refrain from this frenzied growth spurt, and can withstand over two weeks underwater, able to survive the sudden floods of the summer monsoon.

Salt-tolerant rice: Made by inserting an area of the genome called Saltol, salt-tolerant rice varieties are better able to regulate the amount of sodium ions, toxic in high amounts, in their tissues. Saltol has been incorporated into high-yield varieties throughout the world.

Questions or comments on this article? E-mail us at feedback@sciencenews.org

A version of this article appears in the September 25, 2021 issue of Science News.

CITATIONS

T.M. Chaloner et alPlant pathogen infection risk tracks global crop yields under climate changeNature Climate Change. Vol. 11. Aug. 5, 2021. doi: 10.1038/s41558-021-01104-8

S.C. Clemens et al. Remote and local drivers of Pleistocene South Asian summer monsoon precipitation: A test for future predictionsScience Advances. Vol. 7. June 4, 2021. doi: 10.1126/sciadv.abg3848

A.S. Alisjahbana and D.L. Jock Hoi. Ready for the Dry Years: Building resilience to drought in South-East Asia (2nd edition). United Nations (Economic and Social Commission for Asia and the Pacific) and the Association of Southeast Asian Nations. 2021.

E.M. Muehe et al. Rice production threatened by coupled stresses of climate and soil arsenicNature Communications. Vol. 10. Nov. 1, 2019. doi: 10.1038/s41467-019-12946-4.

D.L. Swain et al. Increasing precipitation volatility in twenty-first-century CaliforniaNature Climate Change. Vol. 8. April 23, 2018. doi: 10.1038/s41558-018-0140-y

Nikk Ogasa

About Nikk Ogasa

Nikk Ogasa was a summer 2021 science writer intern. He has a master’s degree in geology from McGill University, and a master’s degree in science communication from the University of California, Santa Cruz. He lives in Santa Cruz, Calif.

Read Full Post »

AGRILINKS EVENT

Nutrition and Climate Change: World Food Prize Laureates on Implications for Feed the Future and Achieving the SDGs

Oct 21, 2021onlineLaureates will share insights and key messages for USAID, Feed the Future, and a wide network of partners. CLIMATE AND NATURAL RESOURCES

Read Full Post »

Rice feeds half the world. Climate change’s droughts and floods put it at risk

Scientists and growers will need to innovate to save the staple crop

an aerial photo of rice fields
In a severe drought, rice farmers in California’s Sacramento Valley have to leave some of their fields unplanted (upper left).CALIFORNIA RICE COMMISSION, BRIAN BAER

Share this:

By Nikk Ogasa

SEPTEMBER 24, 2021 AT 6:00 AM

Under a midday summer sun in California’s Sacramento Valley, rice farmer Peter Rystrom walks across a dusty, barren plot of land, parched soil crunching beneath each step.

In a typical year, he’d be sloshing through inches of water amid lush, green rice plants. But today the soil lies naked and baking in the 35˚ Celsius (95˚ Fahrenheit) heat during a devastating drought that has hit most of the western United States. The drought started in early 2020, and conditions have become progressively drier.

Low water levels in reservoirs and rivers have forced farmers like Rystrom, whose family has been growing rice on this land for four generations, to slash their water use.

Rystrom stops and looks around. “We’ve had to cut back between 25 and 50 percent.” He’s relatively lucky. In some parts of the Sacramento Valley, depending on water rights, he says, farmers received no water this season.

California is the second-largest U.S. producer of rice, after Arkansas, and over 95 percent of California’s rice is grown within about 160 kilometers of Sacramento. To the city’s east rise the peaks of the Sierra Nevada, which means “snowy mountains” in Spanish. Rice growers in the valley below count on the range to live up to its name each winter. In spring, melting snowpack flows into rivers and reservoirs, and then through an intricate network of canals and drainages to rice fields that farmers irrigate in a shallow inundation from April or May to September or October.

If too little snow falls in those mountains, farmers like Rystrom are forced to leave fields unplanted. On April 1 this year, the date when California’s snowpack is usually at its deepest, it held about 40 percent less water than average, according to the California Department of Water Resources. On August 4, Lake Oroville, which supplies Rystrom and other local rice farmers with irrigation water, was at its lowest level on record.

a barren muddy field
Drought in the Sacramento Valley has forced Peter Rystrom and other rice farmers to leave swaths of land barren.N. OGASA

Not too long ago, the opposite — too much rain — stopped Rystrom and others from planting. “In 2017 and 2019, we were leaving ground out because of flood. We couldn’t plant,” he says. Tractors couldn’t move through the muddy, clay-rich soil to prepare the fields for seeding.

Climate change is expected to worsen the state’s extreme swings in precipitation, researchers reported in 2018 in Nature Climate Change. This “climate whiplash” looms over Rystrom and the other 2,500 or so rice producers in the Golden State. “They’re talking about less and less snowpack, and more concentrated bursts of rain,” Rystrom says. “It’s really concerning.”

Farmers in China, India, Bangladesh, Indonesia, Vietnam — the biggest rice-growing countries — as well as in Nigeria, Africa’s largest rice producer — also worry about the damage climate change will do to rice production. More than 3.5 billion people get 20 percent or more of their calories from the fluffy grains. And demand is increasing in Asia, Latin America and especially in Africa.

To save and even boost production, rice growers, engineers and researchers have turned to water-saving irrigation routines and rice gene banks that store hundreds of thousands of varieties ready to be distributed or bred into new, climate-resilient forms. With climate change accelerating, and researchers raising the alarm about related threats, such as arsenic contamination and bacterial diseases, the demand for innovation grows.

“If we lose our rice crop, we’re not going to be eating,” says plant geneticist Pamela Ronald of the University of California, Davis. Climate change is already threatening rice-growing regions around the world, says Ronald, who identifies genes in rice that help the plant withstand disease and floods. “This is not a future problem. This is happening now.”

The top rice producers are in Asia

The world’s top rice producer is China, at 214 million metric tons. India, Bangladesh, Indonesia and Vietnam are next. In Africa, Nigeria (6.8 million) is the largest producer. Brazil (11.8 million) and the United States (10.2 million) are also top producers, according to 2018 data from the U.N. Food and Agriculture Organization.

Worldwide rice production, 2018
a map showing where rice is grown around the world
OURWORLDINDATA.ORG

SOURCE: FAO

Saltwater woes

Most rice plants are grown in fields, or paddies, that are typically filled with around 10 centimeters of water. This constant, shallow inundation helps stave off weeds and pests. But if water levels suddenly get too high, such as during a flash flood, the rice plants can die.

Striking the right balance between too much and too little water can be a struggle for many rice farmers, especially in Asia, where over 90 percent of the world’s rice is produced. Large river deltas in South and Southeast Asia, such as the Mekong River Delta in Vietnam, offer flat, fertile land that is ideal for farming rice. But these low-lying areas are sensitive to swings in the water cycle. And because deltas sit on the coast, drought brings another threat: salt.

Salt’s impact is glaringly apparent in the Mekong River Delta. When the river runs low, saltwater from the South China Sea encroaches upstream into the delta, where it can creep into the soils and irrigation canals of the delta’s rice fields.

a farmer's hand holding dead rice plants being pulled from a paddy
In Vietnam’s Mekong River Delta, farmers pull dead rice plants from a paddy that was contaminated by saltwater intrusion from the South China Sea, which can happen during a drought.HOANG DINH NAM/AFP VIA GETTY IMAGES

“If you irrigate rice with water that’s too salty, especially at certain [growing] stages, you are at risk of losing 100 percent of the crop,” says Bjoern Sander, a climate change specialist at the International Rice Research Institute, or IRRI, who is based in Vietnam.

In a 2015 and 2016 drought, saltwater reached up to 90 kilometers inland, destroying 405,000 hectares of rice paddies. In 2019 and 2020, drought and saltwater intrusion returned, damaging 58,000 hectares of rice. With regional temperatures on the rise, these conditions in Southeast Asia are expected to intensify and become more widespread, according to a 2020 report by the Economic and Social Commission for Asia and the Pacific.

Then comes the whiplash: Each year from around April to October, the summer monsoon turns on the faucet over swaths of South and Southeast Asia. About 80 percent of South Asia’s rainfall is dumped during this season and can cause destructive flash floods.

Bangladesh is one of the most flood-prone rice producers in the region, as it sits at the mouths of the Ganges, Brahmaputra and Meghna rivers. In June 2020, monsoon rains flooded about 37 percent of the country, damaging about 83,000 hectares of rice fields, according to Bangladesh’s Ministry of Agriculture. And the future holds little relief; South Asia’s monsoon rainfall is expected to intensify with climate change, researchers reported June 4 in Science Advances.

Sign Up For the Latest from Science News

Headlines and summaries of the latest Science News articles, delivered to your inboxE-mail Address*GO

A hot mess

Water highs and lows aren’t the entire story. Rice generally grows best in places with hot days and cooler nights. But in many rice-growing regions, temperatures are getting too hot. Rice plants become most vulnerable to heat stress during the middle phase of their growth, before they begin building up the meat in their grains. Extreme heat, above 35˚ C, can diminish grain counts in just weeks, or even days. In April in Bangladesh, two consecutive days of 36˚ C destroyed thousands of hectares of rice.

In South and Southeast Asia, such extreme heat events are expected to become common with climate change, researchers reported in July in Earth’s Future. And there are other, less obvious, consequences for rice in a warming world.

One of the greatest threats is bacterial blight, a fatal plant disease caused by the bacterium Xanthomonas oryzae pv. oryzae. The disease, most prevalent in Southeast Asia and rising in Africa, has been reported to have cut rice yields by up to 70 percent in a single season.

“We know that with higher temperature, the disease becomes worse,” says Jan Leach, a plant pathologist at Colorado State University in Fort Collins. Most of the genes that help rice combat bacterial blight seem to become less effective when temperatures rise, she explains.

And as the world warms, new frontiers may open for rice pathogens. An August study in Nature Climate Change suggests that as global temperatures rise, rice plants (and many other crops) at northern latitudes, such as those in China and the United States, will be at higher risk of pathogen infection.

Meanwhile, rising temperatures may bring a double-edged arsenic problem. In a 2019 study in Nature Communications, E. Marie Muehe, a biogeochemist at the Helmholtz Centre for Environmental Research in Leipzig, Germany, who was then at Stanford University, showed that under future climate conditions, more arsenic will infiltrate rice plants. High arsenic levels boost the health risk of eating the rice and impair plant growth.

Leaching in

When grown in a greenhouse at 5 degrees Celsius above preindustrial temperatures with elevated carbon dioxide levels (representing a future climate), California rice varieties absorbed more of a type of highly toxic arsenic from the soil, raising the rice’s arsenic levels above European Union safety thresholds.

Arsenic levels in rice grains
a chart showing arsenic in rice under different climate conditions
CREDIT: E. OTWELL

SOURCE: E.M. MUEHE ET AL/NATURE COMM.2019

Arsenic naturally occurs in soils, though in most regions the toxic element is present at very low levels. Rice, however, is particularly susceptible to arsenic contamination, because it is grown in flooded conditions. Paddy soils lack oxygen, and the microbes that thrive in this anoxic environment liberate arsenic from the soil. Once the arsenic is in the water, rice plants can draw it in through their roots. From there, the element is distributed throughout the plants’ tissues and grains.

Muehe and her team grew a Californian variety of rice in a local low-arsenic soil inside climate-controlled greenhouses. Increasing the temperature and carbon dioxide levels to match future climate scenarios enhanced the activity of the microbes living in the rice paddy soils and increased the amount of arsenic in the grains, Muehe says. And importantly, rice yields diminished. In the low-arsenic Californian soil under future climate conditions, rice yield dropped 16 percent.

According to the researchers, models that forecast the future production of rice don’t account for the impact of arsenic on harvest yields. What that means, Muehe says, is that current projections are overestimating how much rice will be produced in the future.

Managing rice’s thirst

From atop an embankment that edges one of his fields, Rystrom watches water gush from a pipe, flooding a paddy packed with rice plants. “On a year like this, we decided to pump,” he says.

Able to tap into groundwater, Rystrom left only about 10 percent of his fields unplanted this growing season. “If everybody was pumping from the ground to farm rice every year,” he admits, it would be unsustainable.

One widely studied, drought-friendly method is “alternate wetting and drying,” or intermittent flooding, which involves flooding and draining rice paddies on one- to 10-day cycles, as opposed to maintaining a constant inundation. This practice can cut water use by up to 38 percent without sacrificing yields. It also stabilizes the soil for harvesting and lowers arsenic levels in rice by bringing more oxygen into the soils, disrupting the arsenic-releasing microbes. If tuned just right, it may even slightly improve crop yields.

But the water-saving benefits of this method are greatest when it is used on highly permeable soils, such as those in Arkansas and other parts of the U.S. South, which normally require lots of water to keep flooded, says Bruce Linquist, a rice specialist at the University of California Cooperative Extension. The Sacramento Valley’s clay-rich soils don’t drain well, so the water savings where Rystrom farms are minimal; he doesn’t use the method.

Building embankments, canal systems and reservoirs can also help farmers dampen the volatility of the water cycle. But for some, the solution to rice’s climate-related problems lies in enhancing the plant itself.

three men stand next to each other
Fourth-generation rice farmer Peter Rystrom (left) stands with his grandfather Don Rystrom (middle) and his father Steve Rystrom (right).CALIFORNIA RICE COMMISSION, BRIAN BAER

Better breeds

The world’s largest collection of rice is stored near the southern rim of Laguna de Bay in the Philippines, in the city of Los Baños. There, the International Rice Genebank, managed by IRRI, holds over 132,000 varieties of rice seeds from farms around the globe.

Upon arrival in Los Baños, those seeds are dried and processed, placed in paper bags and moved into two storage facilities — one cooled to 2˚ to 4˚ C from which seeds can be readily withdrawn, and another chilled to –20˚ C for long-term storage. To be extra safe, backup seeds are kept at the National Center for Genetic Resources Preservation in Fort Collins, Colo., and the Svalbard Global Seed Vault tucked inside a mountain in Norway.

All this is done to protect the biodiversity of rice and amass a trove of genetic material that can be used to breed future generations of rice. Farmers no longer use many of the stored varieties, instead opting for new higher-yield or sturdier breeds. Nevertheless, solutions to climate-related problems may be hidden in the DNA of those older strains. “Scientists are always looking through that collection to see if genes can be discovered that aren’t being used right now,” says Ronald, of UC Davis. “That’s how Sub1 was discovered.”

two people in blue jumpsuits looking at rice seeds on shelves
Over 132,000 varieties of rice seeds fill the shelves of the climate-controlled International Rice Genebank. Breeders from around the world can use the seeds to develop new climate-resilient rice strains.IRRI/FLICKR (CC BY-NC-SA 2.0)

The Sub1 gene enables rice plants to endure prolonged periods completely submerged underwater. It was discovered in 1996 in a traditional variety of rice grown in the Indian state of Orissa, and through breeding has been incorporated into varieties cultivated in flood-prone regions of South and Southeast Asia. Sub1-wielding varieties, called “scuba rice,” can survive for over two weeks entirely submerged, a boon for farmers whose fields are vulnerable to flash floods.

Some researchers are looking beyond the genetic variability preserved in rice gene banks, searching instead for useful genes from other species, including plants and bacteria. But inserting genes from one species into another, or genetic modification, remains controversial. The most famous example of genetically modified rice is Golden Rice, which was intended as a partial solution to childhood malnutrition. Golden Rice grains are enriched in beta-carotene, a precursor to vitamin A. To create the rice, researchers spliced a gene from a daffodil and another from a bacterium into an Asian variety of rice.

Three decades have passed since its initial development, and only a handful of countries have deemed Golden Rice safe for consumption. On July 23, the Philippines became the first country to approve the commercial production of Golden Rice. Abdelbagi Ismail, principal scientist at IRRI, blames the slow acceptance on public perception and commercial interests opposed to genetically modified organisms, or GMOs (SN: 2/6/16, p. 22).

Looking ahead, it will be crucial for countries to embrace GM rice, Ismail says. Developing nations, particularly those in Africa that are becoming more dependent on the crop, would benefit greatly from the technology, which could produce new varieties faster than breeding and may allow researchers to incorporate traits into rice plants that conventional breeding cannot. If Golden Rice were to gain worldwide acceptance, it could open the door for new genetically modified climate- and disease-resilient varieties, Ismail says. “It will take time,” he says. “But it will happen.”

Climate change is a many-headed beast, and each rice-growing region will face its own particular set of problems. Solving those problems will require collaboration between local farmers, government officials and the international community of researchers.

“I want my kids to be able to have a shot at this,” Rystrom says. “You have to do a lot more than just farm rice. You have to think generations ahead.”

Climate-resilient rice

To keep rice bowls around the world full, researchers breed new varieties of rice that can endure stresses like drought, floods and salt.

Sahbhagi Dhan: Traditional rice varieties take 120 to 150 days to harvest and require four irrigations. Sahbhagi Dhan is a drought-tolerant variety harvested after 105 days and just two irrigations. In normal conditions, it produces about twice as much rice (four to five metric tons per hectare) as other local varieties in India. Under drought conditions, it produces one to two metric tons per hectare; local varieties produce none.

rice paddies
Scuba rice contains a gene that enables the plant to survive several days underwater, important for areas that experience flooding.IRRI/FLICKR (CC BY-NC-SA 2.0)

Scuba riceSub1, a submergence-tolerance gene, has been bred into scuba rice varieties. Rice normally dies after three to four days of total submergence — many varieties will exhaust themselves to death trying to quickly grow to the water’s surface. Sub1 varieties (shown), however, refrain from this frenzied growth spurt, and can withstand over two weeks underwater, able to survive the sudden floods of the summer monsoon.

Salt-tolerant rice: Made by inserting an area of the genome called Saltol, salt-tolerant rice varieties are better able to regulate the amount of sodium ions, toxic in high amounts, in their tissues. Saltol has been incorporated into high-yield varieties throughout the world.

Read Full Post »

What a warmer, wetter world means for insects, and for what they eat

August 30, 2021 11.28am EDT

Author

  1. Esther Ndumi NgumbiAssistant Professor, Department of Entomology; African-American Studies, University of Illinois at Urbana-Champaign

Disclosure statement

Esther Ndumi Ngumbi is a senior Food Security Fellow with the Aspen Institute New Voices.

Partners

View all partners

Republish our articles for free, online or in print, under a Creative Commons license.

Republish this article

new report has been released by the Intergovernmental Panel on Climate Change (IPCC) – the UN’s authority on climate change – which revealed the latest research on how the Earth is changing and what those changes will mean for the future.

The report shows there’s been a dramatic increase in carbon dioxide (CO2) levels and temperatures, stating that Earth is likely to reach the crucial 1.5℃ warming limit in the early 2030s. There are also dramatic changes in precipitation – water that’s released from clouds, such as rain, snow, or hail.

As an entomologist, I study insects and how climate change stressors – such as flooding and drought – affect what insects eat. I’m also a food security advocate.

The report’s projections caused me to reflect on the many direct and indirect impacts that a warmer and wetter world will have on insects, their natural enemies, plants and African food security.


Read more: How changes in weather patterns could lead to more insect invasions


Across the African continent, recent years brought out some of these extremes, showing what a serious issue this is.

For instance, in southern Africa, the 2016 outbreak of the fall armyworm has continued to spread because of increased rainfall and elevated temperatures – perfect conditions for them to breed and grow quickly. These conditions also supported the growth of over 70 host plants that are fed upon by the fall armyworm.

There’s also a major desert locust outbreak in eastern Africa which started in 2019. It spread due to unusually heavy rainfall that created the perfect environment for locusts to breed and increase in numbers and size. The rains also support the growth of vegetation to feed them.

Here I present a closer look at some of the report’s key findings and show how changes could affect insects and, indirectly, us.

Elevated carbon dioxide levels

Global levels of CO₂ are already high, and they’re expected to continue rising. While elevation in CO₂ does not directly impact insects, it can alter plants’ nutritional quality and chemistry. This will indirectly affect insect herbivores.

For instance, according to recent research, elevated CO₂ reduces the nutritional quality of plant tissues by reducing protein concentrations and certain amino acids in the leaves. To compensate, insect herbivores eat more.

Elevated CO₂ levels can also affect an insect’s development, driving down their numbers – as seen in this study of dung beetles.

Rising temperatures

The report says that global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO₂ and other greenhouse gas emissions occur in the coming decades.

Temperature regulates insects’ physiology and metabolism. An increase in temperature increases physiological activity and, therefore, metabolic rates. Insects must eat more to survive and it’s expected that insect herbivores will consume more and grow faster.

This will lead to increases in the population growth rate of certain insects. Because they grow fast they’ll reproduce more. Their numbers will multiply and this will ultimately lead to more crop damage.


Read more: What changes in temperature mean for Africa’s tsetse fly


Previous research projected that with every increase in one degree of global warming, losses of crops to insects will increase from 10% to 25%.

Drought and flooding

The changing climate is expected to change precipitation patterns – such as rainfall. The report anticipates increased and frequent drought and flooding incidences across the world. These environmental stressors will have an impact on plant productivity, plant chemistry, defences, nutritional quality, palatability, and digestibility.

Consequently, insects eat more plants and this can result in more crop damage.

On the other hand, increased precipitation can support fresh vegetation (food for insects) and can facilitate population buildup of insects. As seen with the desert locust, for example, prolonged rain allowed them to have food, multiply in numbers and spread. This was also the case for the fall armyworm; plentiful rains supported the growth of their host plants. When food for the insects is no longer a limiting factor, their populations continue to build up.


Read more: A new model shows where desert locusts will breed next in East Africa


Reducing effectiveness of natural enemies

All insects have natural enemies or predators. For example, the maize stem borer – a significant insect pest of maize across Africa – has several natural enemies, such as Cotesia flavipes. These predators reduce the populations on insects and further reduce the need to use pesticides to control insect pests.

Predators can be affected by climate changes in many ways. For instance, they can be sensitive to increases in temperature and precipitation, ultimately reducing their numbers. Fewer natural enemies could result in more insect pests. One study, which modelled temperature changes on stem borers in East Africa, showed an increase in their numbers and a decrease in impact by natural enemies.

In addition, because of climate change, both crop distribution ranges and insects will shift. As they seek out conditions that suit them, insects move to new areas that lack their natural enemies. This will cause their populations to grow, resulting in more crop damage.

More palatable food

Because of climate change, weather extremes are likely to happen together.

According to researchplants exposed to double stresses may become even more palatable to insects. This is because when two stressors (say drought and insect herbivory, flooding and insect herbivory, or elevated carbon dioxide and elevated heat) happen together, their impact on crops can be additive or synergistic. This would lead to increased crop damage and reduced crop yields.

What can be done?

Climate change will affect agricultural plants and the insects associated with them. These effects are complex, but it is certain pest pressures will increase. There is a need for more insect monitoring and forecasting and modelling so that we can develop adaptation strategies.

In addition, countries should continue to monitor, share information, and use historical data and modelling to predict and prepare for an uncertain future that is expected to have hungrier insect pests, with impacts on crop productivity and food security.

How The Conversation is different

Every article you read here is written by university scholars and researchers with deep expertise in their subjects, sharing their knowledge in their own words. We don’t oversimplify complicated issues, but we do explain and clarify. We believe bringing the voices of experts into the public discourse is good for democracy.

Find out more

Beth Daley

Editor and General Manager

You might also like

African countries should turn to lower risk solutions to fight fall armyworm

Explainer: what’s behind the locust swarms damaging crops in southern Africa

Tracing the history of farming across Africa gives clues to low production outputs

Read Full Post »

From PestNet

Saturday, 04 September 2021 10:28:00

Grahame Jackson posted a new submission ‘High altitudes no longer protect pine trees from disease’

Submission

High altitudes no longer protect pine trees from disease

erath.com

ByAlison Bosman

Earth.com staff writer

Researchers from UC Davis have gathered some of the first scientific evidence that climate change can affect the distribution of pathogens. The team studied the incidence of white pine blister rust in the forests of the Sequoia and Kings Canyon National Parks. White pine blister rust is caused by a fungus Cronartium ribicola that infects several types of pine trees, including whitebark pine, and has caused serious damage to white pine populations in the United States. 

The pathogen was introduced by accident in 1900 and is an invasive species that inevitably causes tree mortality. Part of the life cycle of C. ribicola is completed in secondary hosts, namely currant and gooseberry plants.

In the past, blister rust infections did not occur in high-altitude forests because the pathogen prefers warmer, milder conditions. Consequently, the forests above the Sequoia and Kings Canyon National Parks acted as a refuge from this disease. However, with changing climatic conditions, the pathogen has begun to infect trees that are higher up the slopes. 

“Because pathogens have thermal tolerances, we are seeing expansions and contractions in this disease’s range,” said study lead author Joan Dudney, a postdoctoral researcher at UC Davis in the lab of Professor Andrew Latimer. “Climate change isn’t so much leading to widespread increases in this disease but rather shifting where it is emerging.”

The researchers used data from long-term monitoring plots in the National Park forests in the southern Sierra Nevada mountains. Data spanned the period between 1996 and 2016, which is considered to be a warmer, drier period than normal. Observations from over 7,800 potential host trees were included and, in addition, the scientists measured stable isotope ratios in pine needles. 

They found that the optimal climatic conditions for blister rust moved, during the 20-year study period, from lower to higher elevations. The incidence of blister rust decreased by 5.5 percent in the more arid, lower-elevation forests and increased by 7 percent in forests at cooler, higher elevations.

“Our study clearly demonstrates that infectious plant diseases are moving upslope, and they’re moving fast,” said Dudney. “Few pines are resistant to what is basically a Northern Hemisphere white pine pandemic.”

The high-elevation refuges where pine trees were protected from pathogens by the inhospitable conditions, are now under threat because of climate warming; conditions there are becoming tolerable to the diseases and pests. Pathogens are expanding their ranges into these higher elevation areas while contracting in the lower areas where the climate is now too warm and dry for their survival.

“It’s kind of a race between evolution and climate change,” said Professor Latimer. “So far, climate change is winning.”

Although it seems inevitable that blister rust will impact severely on white pine populations as the climate becomes warmer, Dudney stated that employing disease prevention methods could help to slow the spread of the disease. 

The study is published recently in the journal Nature Communications.

Saturday, 04 September 2021 10:28:00


Read Full Post »

SEPTEMBER 1, 2021

Soil legacy effect of global change influences invasiveness of alien plants

by Zhang Nannan, Chinese Academy of Sciences

Soil legacy effect of global change influences invasiveness of alien plants
The common garden experiment in Xishuangbanna. Credit: SHI Xiong

Global change characterized by land use change and extreme precipitation has emerged as a challenge for tropical forests in Southeast Asia. Numerous studies have indicated that these changes could affect soil ecology. However, it remains unclear whether land use change and extreme precipitation influence plant invasiveness in tropical forests.

In a study published in Environmental and Experimental Botany, researchers from the Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences conducted a full factorial experiment to test the soil legacy effect of extreme precipitation and land use change on the absolute and relative biomass production of invasive plants in tropical forests.

The researchers mixed Chromolaena odorata, one of the most invasive plants in southern China, separately with two common co-occurring native species in the soil, and exposed them to three water supply levels (drought, normal, rainfall) and two soil microorganism treatments (ambient and sterile) collected from three forests (primary, rubber and secondary forests) in Xishuangbanna.

They found that drought increased the availability of phosphorus in the soil of tropical forest. Chromolaena odorata had a greater total biomass but a lower biomass fraction in secondary forest soil than in primary forest and rubber plantation soil.

The soil legacy effect of drought was positive on both the biomass and biomass fraction of C. odorata. A higher soil organic carbon content and available phosphorous were found in the secondary forest, and both the biomass and biomass proportion were increased by sterilization in this kind of soil.

They further found that increased precipitation increased invasive potential in rubber plantations. The biomass and biomass fraction of C. odorata under rainfall was greater than that under the control treatment.

Moreover, the microbial legacy effects had a negative impact on alien invasiveness. The invader was suppressed by microorganisms more than native species were. Thus, microorganisms in secondary forest soil might be a key factor mediating the coexistence of invaders and native species.

“Our study demonstrated the pronounced soil legacy effect of land use change, extreme precipitation and their interactions on the invasion success of C. odorata,” said Zheng Yulong, principal investigator of the study.


Explore furtherEcosystem functions of rubber plantations are lower than tropical forests


More information: Xiong Shi et al, Soil legacy effect of extreme precipitation on a tropical invader in different land use types, Environmental and Experimental Botany (2021). DOI: 10.1016/j.envexpbot.2021.104625Provided by Chinese Academy of Sciences

Read Full Post »

Science News from research organizations


Urban lights keep insects awake at night

Scientists reveal how the urban-related increase in nighttime light and heat postpones natural hibernation periods of flesh flies

Date:August 18, 2021Source: Osaka City University Summary: New research sheds light on the effect urbanization has on the flesh fly species Sarcophaga similis. Through a series of laboratory and in-field experiments, scientists show that an increase in nighttime illumination and temperature, two of the major characteristics of urbanization, can postpone S. similis hibernation anywhere from 3 weeks to a month.Share: FULL STORY


A new study shows how an increase in nighttime lighting (light pollution) and heat from urban areas disturbs the hibernation periods of insects.

“The study looks at a species of flesh fly called Sarcophaga similis, but the results could be applicable to any animal species that relies on predictable environmental signals for biological processes like growth, reproductive behavior, sleep, and migration,” said Assistant Professor Ayumu Mukai of Setsunan University and lead author of the study. In collaboration with Professor Shin Goto of Osaka City University, their findings were published in Royal Society Open Science.

A common way of exploring the ecological effects of urbanization is to investigate changes in life cycles of species in the urban and surrounding area. Urban warming and artificial light at night are two of the most influential factors in this regard. As urban warming can increase surface temperatures anywhere between 5 — 9°C, species with lower critical thermal optima, i.e. biological processes such as growth and development that occur at lower environmental temperatures, are disproportionately affected. Due to large fluctuations throughout the day and year, temperature can be an unreliable cue for species to determine when to sleep, breed, migrate, etc., rendering this cue supplemental to a biological response to seasonal changes by monitoring day length — an ability called photoperiodism. Increased nighttime light can throw off an insect’s photoperiodism, yet few studies have focused on the effect urban warming and artificial light at night have had on insects in their natural habitat.

“Recognizing the conditions urbanization brings upon insects where they actually live would be a great step forward in mitigating any negative effects,” Shin Goto said. To understand this, the team conducted experiments indoors and outdoors. As S. similis typically enters hibernation during autumn, laboratory hibernation was induced in flies under two average October temperatures (20°C and 15°C), with varying levels of illuminance to mimic bright urban to dark rural areas. They found that the percentage of flies entering hibernation decreased as illumination increased and as the temperature increased from 15°C to 20°C — suggesting the higher temperatures found in urban areas are associated with higher nighttime illumination.

In the field, the team measured when the insects entered hibernation in two city locations: a site with nighttime lighting at around 0.2 lux (the brightness of a full moon in a clear sky), and another with nighttime lighting at around 6 lux, which is equivalent to a residential area or street at night. At sites with dark nights, most flies enter hibernation between October and November while at sites with increased nighttime light, they did not enter hibernation until after November. The team also compared urban areas with illumination of about 0.2 lux with rural areas of almost 0 lux. The percentages of flies entering hibernation in rural areas increased from late September, around 3 weeks earlier than their urban counterparts. Temperatures were also 2.5°C higher in the cities, which is thought to be the cause for the delay in hibernation.

While these findings do suggest that nighttime lighting, which supports our daily lives, is disrupting the seasonality of insects, “urban environments are complex, with nighttime illumination and temperatures varying within the same neighborhood and between different cities,” Ayumu Mukai pointed out, “and our work on a single flesh fly does not elucidate the photoperiodic response of other insects.”

To understand the extent to which our cultural life influences other organisms, Shin Goto continued, “Future studies with a variety of insect species at different sites, in cities with different climatic regions would clarify what levels of light pollution and urban warming affect insect seasonal adaptation”


Story Source:

Materials provided by Osaka City UniversityNote: Content may be edited for style and length.


Journal Reference:

  1. Ayumu Mukai, Koki Yamaguchi, Shin G. Goto. Urban warming and artificial light alter dormancy in the flesh flyRoyal Society Open Science, 2021; 8 (7): 210866 DOI: 10.1098/rsos.210866

  • Osaka City University. “Urban lights keep insects awake at night: Scientists reveal how the urban-related increase in nighttime light and heat postpones natural hibernation periods of flesh flies.” ScienceDaily. ScienceDaily, 18 August 2021. <www.sciencedaily.com/releases/2021/08/210818130525.htm>.

Read Full Post »

PysOrg

Drought and climate change shift tree disease in Sierra Nevada

by Kat Kerlin, UC Davis

Drought and climate change shift tree disease in sierra nevada
White pines dominate this high-elevation forest at Sequoia and Kings Canyon national parks. Credit: Joan Dudney/UC Davis

Even pathogens have their limits. When it gets too hot or too dry, some pathogens—like many living things—search for cooler, wetter and more hospitable climes. Ecologists have questioned if a warming, drying climate is connected to the spread of plant disease, but detecting a climate change fingerprint has been elusive.

A study from the University of California, Davis, provides some of the first evidence that climate change and drought are shifting the range of infectious disease in forests suffering from white pine blister rust disease.

“Because pathogens have thermal tolerances, we are seeing expansions and contractions in this disease’s range,” said lead author Joan Dudney, a Davis H. Smith postdoctoral fellow at UC Davis in the lab of Professor Andrew Latimer, a study co-author. “Climate change isn’t so much leading to widespread increases in this disease but rather shifting where it is emerging.”

The study, published today in the journal Nature Communications, found that white pine blister rust disease expanded its range into higher-elevation forests in the southern Sierra Nevada between 1996 and 2016. At the same time, it also contracted its range in lower elevations, where conditions were often too hot and dry for its survival.

“Our study clearly demonstrates that infectious plant diseases are moving upslope, and they’re moving fast,” Dudney said. “Few pines are resistant to what is basically a Northern Hemisphere white pine pandemic.”

White pine blister rust disease is caused by a pathogen, Cronartium ribicola, and it has led to a major decline of white pine species throughout the U.S., including whitebark pine, which is in the process of being listed as a threatened species. The study suggests that whitebark pine and many other high-elevation pine species may become increasingly imperiled under climate change.

Drought and climate change shift tree disease in sierra nevada
A research crew surveys trees for white pine blister rust disease in Sequoia and Kings Canyon national parks. Credit: Clayton Boyd

Expanding and contracting

To collect the data, scientists spent five years resurveying long-term monitoring plots in the remote wilderness of Sequoia and Kings Canyon national parks, measuring stable isotope signatures in pine needles and collecting observations for over 7,800 individual host trees. The data includes two surveys that were about 20 years apart. What resulted is one of the first clear measurements of an infectious plant disease range shift into higher elevations.1

They found that the optimal climate for blister rust moved into higher elevations between 1996 and 2016—a warmer, hotter period than the previous two decades. Climate change decreased the prevalence of blister rust disease by 5.5% in arid, lower elevations and increased its prevalence nearly 7% in colder upper elevations. This amounted to an area expansion of about 200,000 acres, which exposed the majority of hosts in Sequoia and Kings Canyon national parks.

Though infection risk increased in the parks, the overall prevalence of the disease declined in the area. That surprising result is partly because many of the infected trees in the lower elevations died between surveys, and it became too warm and dry for new infections to develop there. Meanwhile, the secondary hosts the pathogen requires—such as currant and gooseberry plants—are not abundant at higher elevations, although that could change as the climate warms.

  • Drought and climate change shift tree disease in sierra nevadaHigh-elevation species like white pines in Sequoia and Kings Canyon national parks have adapted to thrive in harsh conditions but not yet to the threats of increased pests and diseases climate change presents. Credit: Joan Dudney/UC Davis
  • Drought and climate change shift tree disease in sierra nevadaSpores from white pine blister rust disease infect a pine tree in Sequoia and Kings Canyon national parks. Credit: Clayton Boyd
  • Drought and climate change shift tree disease in sierra nevadaHigh-elevation species like white pines in Sequoia and Kings Canyon national parks have adapted to thrive in harsh conditions but not yet to the threats of increased pests and diseases climate change presents. Credit: Joan Dudney/UC Davis
  • Drought and climate change shift tree disease in sierra nevadaSpores from white pine blister rust disease infect a pine tree in Sequoia and Kings Canyon national parks. Credit: Clayton Boyd

An evolutionary race

For white pines, the forests above Sequoia and Kings Canyon national parks have long served as a small refuge from white pine blister rust, but the projected expansion of the disease under climate change threatens that refuge, the study suggests.

The authors said that white pines in the study area’s upper elevations are “disease-naïve.” The same harsh conditions they adapted to also restricted most diseases and pests. Climate change is shifting those constraints quickly, leaving the trees more vulnerable.

“It’s kind of a race between evolution and climate change,” Latimer said. “So far, climate change is winning.”

While the white pine outlook appears grim, Dudney said being proactive about disease prevention could help slow the spread and detect new invasions.

“Once they’ve experienced an epidemic, we have little recourse but to triage the area,” Dudney said.


Explore furtherWhitebark pine declines may unravel the tree’s mutualism with Clark’s Nutcracker


More information: Joan Dudney et al, Nonlinear shifts in infectious rust disease due to climate change, Nature Communications (2021). DOI: 10.1038/s41467-021-25182-6Journal information:Nature CommunicationsProvided by UC Davis

Read Full Post »

OPINION

Protecting Plants Will Protect People and the Planet

ISA Inerpress News Agency

By Barbara WellsReprint |         |  Print | Send by email

ROME, Jul 26 2021 (IPS) – Back-to-back droughts followed by plagues of locusts have pushed over a million people in southern Madagascar to the brink of starvation in recent months. In the worst famine in half a century, villagers have sold their possessions and are eating the locusts, raw cactus fruits, and wild leaves to survive.

Barbara WellsInstead of bringing relief, this year’s rains were accompanied by warm temperatures that created the ideal conditions for infestations of fall armyworm, which destroys mainly maize, one of the main food crops of sub-Saharan Africa.

Drought and famine are not strangers to southern Madagascar, and other areas of eastern Africa, but climate change bringing warmer temperatures is believed to be exacerbating this latest tragedy, according to The Deep South, a new report by the World Bank.

Up to 40% of global food output is lost each year through pests and diseases, according to FAO estimates, while up to 811 million people suffer from hunger. Climate change is one of several factors driving this threat, while trade and travel transport plant pests and pathogens around the world, and environmental degradation facilitates their establishment.

Crop pests and pathogens have threatened food supplies since agriculture began. The Irish potato famine of the late 1840s, caused by late blight disease, killed about one million people. The ancient Greeks and Romans were well familiar with wheat stem rust, which continues to destroy harvests in developing countries.

But recent research on the impact of temperature increases in the tropics caused by climate change has documented an expansion of some crop pests and diseases into more northern and southern latitudes at an average of about 2.7 km a year.

Prevention is critical to confronting such threats, as brutally demonstrated by the impact of the COVID-19 pandemic on humankind. It is far more cost-effective to protect plants from pests and diseases rather than tackling full-blown emergencies.

One way to protect food production is with pest- and disease-resistant crop varieties, meaning that the conservation, sharing, and use of crop biodiversity to breed resistant varieties is a key component of the global battle for food security.

CGIAR manages a network of publicly-held gene banks around the world that safeguard and share crop biodiversity and facilitate its use in breeding more resistant, climate-resilient and productive varieties. It is essential that this exchange doesn’t exacerbate the problem, so CGIAR works with international and national plant health authorities to ensure that material distributed is free of pests and pathogens, following the highest standards and protocols for sharing plant germplasm. The distribution and use of that germplasm for crop improvement is essential for cutting the estimated 540 billion US dollars of losses due to plant diseases annually.

Understanding the relationship between climate change and plant health is key to conserving biodiversity and boosting food production today and for future generations. Human-driven climate change is the challenge of our time. It poses grave threats to agriculture and is already affecting the food security and incomes of small-scale farming households across the developing world.

We need to improve the tools and innovations available to farmers. Rice production is both a driver and victim of climate change. Extreme weather events menace the livelihoods of 144 million smallholder rice farmers. Yet traditional cultivation methods such as flooded paddies contribute approximately 10% of global man-made methane, a potent greenhouse gas. By leveraging rice genetic diversity and improving cultivation techniques we can reduce greenhouse gas emissions, enhance efficiency, and help farmers adapt to future climates.

We also need to be cognizant that gender relationships matter in crop management. A lack of gender perspectives has hindered wider adoption of resistant varieties and practices such as integrated pest management. Collaboration between social and crop scientists to co-design inclusive innovations is essential.

Men and women often value different aspects of crops and technologies. Men may value high yielding disease-resistant varieties, whereas women prioritize traits related to food security, such as early maturity. Incorporating women’s preferences into a new variety is a question of gender equity and economic necessity. Women produce a significant proportion of the food grown globally. If they had the same access to productive resources as men, such as improved varieties, women could increase yields by 20-30%, which would generate up to a 4% increase in the total agricultural output of developing countries.

Practices to grow healthy crops also need to include environmental considerations. What is known as a One Health Approach starts from the recognition that life is not segmented. All is connected. Rooted in concerns over threats of zoonotic diseases spreading from animals, especially livestock, to humans, the concept has been broadened to encompass agriculture and the environment.

This ecosystem approach combines different strategies and practices, such as minimizing pesticide use. This helps protect pollinators, animals that eat crop pests, and other beneficial organisms.

The challenge is to produce enough food to feed a growing population without increasing agriculture’s negative impacts on the environment, particularly through greenhouse gas emissions and unsustainable farming practices that degrade vital soil and water resources, and threaten biodiversity.

Behavioral and policy change on the part of farmers, consumers, and governments will be just as important as technological innovation to achieve this.

The goal of zero hunger is unattainable without the vibrancy of healthy plants, the source of the food we eat and the air we breathe. The quest for a food secure future, enshrined in the UN Sustainable Development Goals, requires us to combine research and development with local and international cooperation so that efforts led by CGIAR to protect plant health, and increase agriculture’s benefits, reach the communities most in need.

Barbara H. Wells MSc, PhD is the Global Director of Genetic Innovation at the CGIAR and Director General of the International Potato Center. She has worked in senior-executive level in the agricultural and forestry sectors for over 30 years.https://platform.twitter.com/widgets/follow_button.f88235f49a156f8b4cab34c7bc1a0acc.en.html#dnt=false&id=twitter-widget-0&lang=en&screen_name=IPSNewsUNBureau&show_count=false&show_screen_name=true&size=l&time=1629524871809

Read Full Post »

Monday, 16 August 2021 18:07:17 PestNet

Grahame Jackson posted a new submission ‘Plant pathogen infection risk tracks global crop yields under climate change’

Submission

Plant pathogen infection risk tracks global crop yields under climate change

Nature
https://www.nature.com/articles/s41558-021-01104-8

·  Thomas M. Chaloner

·  Sarah J. Gurr & 

·  Daniel P. Bebber 

Abstract

Global food security is strongly determined by crop production. Climate change-induced losses to production can occur directly or indirectly, including via the distributions and impacts of plant pathogens. However, the likely changes in pathogen pressure in relation to global crop production are poorly understood. Here we show that temperature-dependent infection risk, r(T), for 80 fungal and oomycete crop pathogens will track projected yield changes in 12 crops over the twenty-first century. For most crops, both yields and r(T) are likely to increase at high latitudes. In contrast, the tropics will see little or no productivity gains, and r(T) is likely to decline. In addition, the United States, Europe and China may experience major changes in pathogen assemblages. The benefits of yield gains may therefore be tempered by the greater burden of crop protection due to increased disease and unfamiliar pathogens.


Read Full Post »

Older Posts »