Can we feed the world without breaking the planet?

The world's population continues to grow, and everybody needs to eat. Producing enough healthy, affordable food is a triumph of modern agriculture, but manipulating plants and animals to our own ends has not been without consequences.

A network of researchers across Cambridge is investigating all aspects of the global food system and asking: is it possible to have a highly productive system that doesn’t cause collateral damage?

“We’ve globalised the whole agricultural system and made it incredibly complex. It’s completely unsustainable because we're taking more out of the environment than the environment can sustain," says Lynn Dicks, Professor of Ecology in the Department of Zoology, adding:

"If you consider nature as capital, it’s like liquidating your assets."

Agriculture is the number one cause of biodiversity loss, and Dicks has found herself studying it because of her love of bees. As pollinators, bees and many other insects provide vital unpaid labour - helping farmers produce three quarters of all our major food crops - but their populations have plummeted since the rise of modern industrialised farming. Many bird species fare badly on farmland too.

“The numbers of bees, other insects, and birds are declining alarmingly. The main causes are loss of habitat - the worst thing you can do for biodiversity is turn natural habitat into farmland - and pesticide use, because many of these chemicals are designed to kill insects,” says Dicks, who co-Chairs the Cambridge Global Food Systems Interdisciplinary Research Centre.

Synthetic pesticides and herbicides have been widely used in farming since the 1940s to kill or control plants, insects and fungi that threaten crop yields. Growing awareness of the environmental and health risks they pose has led to better regulation and monitoring. But outright bans leave farmers scrambling for new solutions.

Professor Sebastian Eves-van den Akker, Head of Plant-Parasite Interactions at the Crop Science Centre, leads one of the few research groups in the world trying to understand potato cyst nematodes, which pose a problem for potato farmers globally. Potatoes have limited resistance to these microscopic, soil-dwelling worms, which can cause yield losses of up to 80%. With the UK government’s recent ban of the chemicals used to control it, farmers are extremely concerned.

“These nematodes go undetected in the soil. They pierce potato roots using a needle-like structure on their head, get inside, and make the potato plant grow a new pseudo organ - a cyst - that they feed from,” says Eves-van den Akker. “The plants can tolerate a small amount of infection, but once this gets over a certain threshold, yields plummet.”

Although plant parasitic nematodes have been around for at least 100 million years, modern intensive agriculture is making them a big problem. The nematode population builds and builds in the soil without farmers knowing, and by the time they realise what’s going on it’s incurable - the nematodes will essentially be in the field forever.

Around half of all UK fields now have potato cyst nematodes in the soil.

They were accidentally imported with potatoes from South America after the Irish potato famine, when farmers wanted to breed blight-resistant crops. Now, they’ve been accidentally spread across the whole world - making them one of the biggest problems in potato farming.

"The farming industry is utterly panicking because there isn't a good replacement for chemical controls."

"We must find solutions that are environmentally sustainable and affordable, so high and low-input systems both benefit,” says Eves-van den Akker.

He’s developed a large-scale genetic screening programme to look for solutions. He’s created an army of 3D-printed robots to manipulate and photograph infected plant roots on a huge scale, and has trained an AI model to recognise when nematodes are in the images. By correlating the plant’s genetic characteristics with the number of nematodes infecting it, his aim is to pinpoint the plant genes underlying susceptibility to infection.

“There’s a finely tuned molecular dialogue between the nematode and the potato plant that ultimately results in crop losses. I want to try to understand enough about the system to be able to break it,” he says, adding:

"My aim is to make a potato plant that’s naturally resistant to infection, either by breeding in resistance genes, or breeding out susceptibility genes."

He’s proved the genetic screening system works in a model plant, and the next step is to transfer it to screen potatoes. The technology is already available to others - to try and speed up the rate at which key genes are identified - and is in the early stages of industry adoption.

Given that every major plant food crop can be parasitised by some kind of nematode, the potential impact of this research, at a time when harmful chemicals are being banned, is huge.

A chemical-free approach to farming is far superior in terms of protecting biodiversity. But until a new generation of pest-resistant crops becomes available, yields of crops grown without chemical pesticides and fertilisers are generally much lower. Zoom out, and overall this means that much more farmland is needed.

Dicks and her research group are looking to farmers across the world for solutions.

“We don't want to design a new farming system from inside our ivory tower and then try and impose it on the world,” she says. “We’re looking for places where farmers are coming up with solutions themselves, and then bringing high quality, rigorous scientific evaluation to look for the ones that are really delivering on all fronts.”

Regenerative Agriculture is one such farmer-led concept, and Dicks is leading work within the £6 million ‘Healthy Soil, Healthy Food, Healthy People’ project (funded by the UKRI’s Transforming UK Food Systems Strategic Priorities Fund) to evaluate its benefits.

“Regenerative Agriculture is not a scientifically-derived idea, and we want to see if it delivers on the hype - that it produces consistently high yields of good quality food, stores carbon in the soil so helps to mitigate climate change, supports biodiversity, and the farmers make more profit because less synthetic chemicals are needed. If it’s this amazing, who wouldn’t do it?”

The project team is still analysing data, but already there’s evidence of clear benefits to soil health and on-farm biodiversity from regenerative farming. But food yields - the primary aim of any type of farming - appear less consistent and sometimes lower than from farms taking a more intensive approach.

The big question is whether regenerative systems can become more stable and productive over time, as farmers learn how to manage the environment regeneratively - allowing the health of soils, pollinators and natural enemies to recover. Plant breeders also need to develop crop varieties that thrive and are highly productive in lower input systems.

"Twentieth century agriculture pushed a standardised approach that was the same everywhere. I don't think that's a good future for food production."

"We’ve realised from our work that the best farming system is very dependent on the local environment, and getting good results relies on local knowledge. There's no one perfect system,” says Dicks.

She adds: “Obviously we need agricultural land to produce our food, but it benefits the majority of wild species to have more natural habitat. There's quite a powerful argument that we should be farming as intensively as possible.”

“For the sake of biodiversity we need to get as much food out of as little land as we can possibly get away with, but for the sake of future food production, we need to do this without destroying agricultural ecosystems themselves. This is the great challenge of the twenty-first century.”

When it comes to livestock, the move to intensive farming also drives new problems. Rearing large numbers of animals together, particularly in highly intensive indoor systems, provides the opportunity for diseases to spread easily, leading to inevitable deaths and requiring antibiotics to keep under control.

For example, Streptococcus suis - a leading cause of disease on pig farms – was rarely a problem in the low-density, free range pig farming of the past. Dr Lucy Weinert, an evolutionary biologist in the Department of Veterinary Medicine studies the various strains of this bug to understand how it is evolving.

“We’ve found six dominant strains of Strep suis, which cause around 80% of the disease in pigs. They’re genetically distinct to other less harmful strains that have been around for hundreds of thousands of years,” she says. “When we traced back the emergence of the pathogenic strains, we found their spread correlates with major changes in pig production methods."

"The intensification of pig farming very likely drove this bug to become more harmful to pigs."

Weinert’s work was part of an international study that found the global spread of the pathogenic strains of Strep suis mirrored the trade in live pigs. The latest worrying development is a dual threat - the emergence of new strains in Thailand not only resistant to the frontline antibiotic class, beta-lactams, used to control infections, but also inherently zoonotic with the ability to cause disease in humans.

“In the UK we don’t see any beta-lactam resistance at all, probably due to very careful use of antibiotics on pig farms,” she says, “and the main impact of Strep suis here is to reduce farm productivity. But in Thailand where there are fine economic balances to be had, antibiotics are poorly regulated and are being used preventatively. There, Strep suis is the leading cause of adult bacterial meningitis in humans, contracted by eating undercooked pork.”

"Intensive pig farming seems to have caused the emergence of a multi-drug resistant zoonotic pathogen that doctors are now struggling to treat."

“As economies emerge and people want to eat more cheap animal protein, farming must intensify to feed everyone,” says Dan Tucker, Professor of Veterinary Public Health in the Department of Veterinary Medicine.

“But intensification can be really risky for disease emergence and transmission, particularly when farmers try to take intensive livestock production methods created in developed economies and apply them in less well-regulated, less well-developed economies,” he adds.

By understanding more about how and where the disease-causing strains of Strep suis grow on the pigs’ bodies, Weinert and Tucker want to design surveillance programmes to identify carrier pigs, so they can be segregated and the strains quickly eliminated. They’ve also done work to identify candidate vaccines, which have shown early success in trials. At present there is no effective vaccine.

"My sense is that intensive livestock production is an evil we have to try and live with - it isn't going to go away."

"But we need to be very careful how we do it,” says Tucker.

From declining biodiversity to the rise of pests and pathogens, modern agriculture has pushed natural systems out of kilter. These researchers are part of a University of Cambridge-wide network working to find a new balance. Genetic manipulation and AI will be vital tools in making food production sustainable for the long term, but so too will a deep understanding of farming practices around the world.