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

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

 

 

By Rebecca Dzombak

 

 

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

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

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

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

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

 

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

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

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

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

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

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

 

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

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

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

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

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

 

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

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

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

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

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

 

 

Why Vermont farmers, USA, are using pasteurised urine on their crops

 

 In Vermont, pasteurised urine is sprayed on local farmland to fertilise crops (Credit: Rich Earth Institute)

 Becca Warner

 

Urine was used as fertiliser in ancient Rome and China. Now farmers in Vermont are bringing this practice back to boost harvests and grow crops in a more sustainable way.

When Betsy Williams goes to the loo, she likes to know her pee won't go to waste. For the last 12 years, she and her neighbours in rural Vermont, US, have diligently collected their urine and donated it to farmers for use as fertiliser for their crops.

"We're consuming all of these things that have nutrients in them, and then a lot of the nutrients that are passing through us can then get recycled back into helping create food for us and for animals. So to me, it's logical," Williams says.

Williams takes part in the Urine Nutrient Reclamation Program (UNRP), a programme run by the Rich Earth Institute (REI), a non-profit based in Vermont. She and 250 of her neighbours in Windham County donate a total of 12,000 gallons (45,400 litres) of urine to the programme each year to be recycled – or "peecycled". 

Windham County's pee-donations are collected by a lorry and driven to a large tank where the urine is pasteurised by heating it to 80C (176F) for 90 seconds. It is then stored in a pasteurised tank, ready to be sprayed on local farmland when the time is right to fertilise crops.

 

Records suggest that urine was used to help grow crops back in ancient China and ancient Rome. Today, scientists are finding that it can more than double the yield of crops like kale and spinach compared to no fertiliser, and improve yields even in low fertility soils.

Urine's power as a fertiliser is due to the nitrogen and phosphorus that it contains – the same nutrients that are added to the synthetic fertilisers used on many conventional farms. But these synthetic fertilisers come at an environmental cost. Nitrogen is produced using the fossil fuel-intensive Haber-Bosch process, and the mining of phosphorus creates harmful amounts of toxic waste. Urine, meanwhile, is freely available – as Williams puts it, "everybody pees. [It's an] untapped resource".

Urine's power as a fertiliser is due to the nitrogen and phosphorus that it contains (Credit: Rich Earth Institute)

Nancy Love, a professor of civil and environmental engineering at the University of Michigan who has collaborated with the team at REI over the last decade, has found that using urine instead of standard synthetic fertiliser reduces greenhouse gas emissions, and requires around half the amount of water. Indeed, since 2012, UNRP estimates that it has conserved over 2.7 million gallons (10.2 million litres) of water through preventing toilet flushes.

"I've always been a systems thinker, and our [water] system has inefficiencies in it," Love says. "What we do today is dilute the hell out of our urine, we put it in a pipe, we send it to a treatment plant, and then we pump a bunch more energy into it, just to send it back into the environment in a reactive form."

 

In the case of urine's nutrients, its typical destination is waterways. The nitrogen and phosphorus in urine are not fully removed from wastewater when it is treated. When these nutrients find their way into rivers and lakes, they are taken up by algae. The result can be algal blooms that choke up waterways, unbalancing the ecosystem and killing other species that live there.

"Our bodies create a lot of nutrients, and right now those nutrients are not only wasted, but they’re actually causing a lot of problems and harm downstream," says Jamina Shupack, REI's executive director.

These nutrients are food for algae – but also for crops. "Wherever you put nitrogen, it's going to help plants grow. So if it's in the water, it's helping the algae grow. But if it's on the land, it's going to help plants grow,” Shupack explains. Because of this, diverting nutrient-rich urine away from waterways and onto the land can prevent harmful algal blooms while helping farmers grow food.

 Everybody pees. It's an untapped resource – Betsy Williams

 Importantly, the REI team and the farmers they work with take steps to minimise how much of the urine runs off the land and into waterways. Application is carefully timed, so that it happens when the plant is most able to take up the nutrients – typically during the plant's more active growth stage, when it's bigger than a seedling but not yet fruiting. The soil moisture is also measured, to make sure the liquid urine will be absorbed. Despite these efforts, "that doesn't mean that there isn't going to be runoff", Shupack says.

 

Even so, she adds, peecycling reduces the overall amount of nutrients entering waterways because it ensures that runoff from the land is the only way excess nutrients enter rivers and lakes. In the current system, synthetic fertilisers run off into waterways, as well as urine entering rivers directly via wastewater.

The UNRP in Vermont is pioneering peecycling in the US, but projects in other countries are also underway. In Paris, volunteers are collecting urine to help save the River Seine and fertilise wheat for baguettes and biscuits. Swedish entrepreneurs saw the harm caused by algal blooms around the island of Gotland and came up with a product that collects urine and turns it into fertiliser. Peecycling pilots have also run in South Africa, Nepal and Niger Republic.

 

Research shows that urine can more than double the yield of certain crops (Credit: Rich Earth Institute)

But expanding this work comes with challenges. Shupack says that in Vermont, farmers' demand for urine outstrips supply – but scaling up collection is tricky. Regulation can create a barrier, she says. "A lot of times you go to a regulator and they say: 'We don't have a form for urine – the only place I know where to put urine is with biosolids, or within wastewater treatment.' So it's not really categorised in a way that would make sense to do what we're doing," she says.

To overcome this, Shupack says that REI have got to grips with the detailed language of regulations so they could spot possible paths and partnered with organisations with existing permits – such as septic haulers – to tackle the different parts of the process, and the permits needed, in a piecemeal way.

 

Eamon Twohig, programme manager at Vermont's Department of Environmental Conservation (VTDEC), tells the BBC that when REI initially approached them "it was clear there was no 'regulatory box' for urine treatment/recycling… REI has certainly blazed a trail here in Vermont, and I think we've managed to find a workable, regulatory pathway."

REI has a good relationship with regulators in Vermont, Shupack says, and has all the permits needed to operate – including one for innovative on-site wastewater management, and a waste-hauling permit for transporting urine. Now the organisation is working with partners in Massachusetts and Michigan to move regulation on. "We're really trying to push that forward. But it's not always easy to get new environmental regulations updated," Shupack says. One of the biggest challenges, she adds, is that there is no legal distinction between human waste that has been separated at source, and combined wastewater flows that often come with greater safety concerns. 

There are other limitations too. Urine is heavy and cumbersome to transport, and the lorries collecting and moving it create emissions. Currently the urine in Vermont is transported locally, no more than around 10 miles (16km). But expanding peecycling programmes could involve moving urine across bigger distances, so REI's spinoff company has developed a freeze concentration system that concentrates urine by six times, and is currently being used at the University of Michigan.

 

Plumbing, too, is a particular challenge. Love says that urine separation systems don't rely on flushing in the same way standard toilets do – which is great for reducing water use, but is problematic for the plumbing. When water doesn't flow through the system as usual, there is a risk of diseases such as Legionnaires.

"There are solutions," Love says, "like looped systems in a building. But what it means is the entire plumbing process in a building is different." This is something Love and her colleagues and partners are working on, so that new buildings in the US can have urine separation systems installed from the start. "If we want any hope of sustainable water systems by the end of this century, we have to start getting the early adopters to look at these innovative solutions now," she says.

The Rich Earth Institute collects a total of 12,000 gallons (45,400 litres) of urine each year (Credit: Rich Earth Institute)

These new systems will have the important goal of making urine donation effortless. Williams began her peecycling efforts using large laundry detergent bottles that travelled in the boot of her car to a central collection tank once a month. Once she was in the habit of collecting urine, Williams didn't like to let it go to waste. "I didn't even like to go anywhere where I might have to pee and not have a jug with me. It kind of became part of my routine, sort of like wearing a seat belt," she says.

Even so, she has enjoyed the recent installation of a toilet in her home that separates urine (at the front) from other waste (at the back). The urine travels to a tank in her basement, which is pumped out a couple of times each year by a lorry that visits Williams and others in her area that take part in the project. "It's a nice change not dealing with the messy business of it. Making it easy for people is a biggie," Williams says.

Avoiding mess is also likely to help tackle the "ick factor" when it comes to peecycling, says Williams. "It's icky and it's smelly and it's something we don't talk about," she says. But while some may be put off by the idea of dealing with their own waste, REI's research suggests that the ick factor doesn't dominate people's reactions to peecycling. People tend to be open to the idea, Shupack says, but to think that others wouldn't be. "It's this assumption that everyone else is going to think it's really gross. That initial ick factor is not as big of a deal as people assume it's going to be," says Shupack.

Many people are, however, concerned about pharmaceutical content in the urine. "It's the biggest question we get," Shupack says. REI has conducted research to find out just how much of common drugs like caffeine and the painkiller acetaminophen are evident in vegetables grown using urine fertiliser. The final results are yet to be released, but the preliminary findings suggest the amount of pharmaceuticals in vegetables fertilised with urine to be "extremely small". "You'd have to eat a pretty obscene amount of lettuce, every day, for way longer than you can live" to get a cup of coffee's worth of caffeine, Shupack says.

Health worries and messiness aside, Williams points out that it is our Western attitude to waste that most urgently needs to change. "Particularly in [the US], people don't really think about where their waste goes. They think about it in terms of recycling and trash to some degree, but not so much in terms of human waste. It's a new frontier for people."

Climate change and water pollution can feel like impossibly big issues, but Williams doesn't let them overwhelm her. Instead, she focuses on what she can do in a small way, in her own home. "We can just do our part," she says. "We aren't perfect, but we try to at least be responsible in terms of what happens to our bodily waste."