Plant pathogens are spreading thanks to climate change and globalisation. The threats to food security need to be taken seriously, says David Burrows.
“As humans we are transfixed by diseases like malaria, HIV and TB, but we don’t think about diseases to crops. It’s about time we did.” That was from an interview I did last year with Sarah Gurr, professor of molecular plant pathology and chair in food security at the University of Exeter. We can now add to that list of diseases Covid-19 – the fight against which now rightly has the focus of the world’s scientists.
But in a paper just published in Nature Food, Gurr and her colleagues highlight the threat of fungal diseases to food security, as pathogens “outmanoeuvre us” and increasingly spread thanks to the globalisation of trade and a changing climate. “We face a future blighted by known adversaries, by new variants of old foes and by new diseases,” Gurr says. “Modern agricultural intensification practices have heightened this challenge.” And climate change “compounds the saga”.
That crops in parts of Africa and Asia are also currently being devastated by, in some cases, the worst swarms of locusts in decades (influence of climate change ‘to be decided’), begs the question: how exposed are foodservice businesses to these risks and will the shock of this pandemic make plant protection a priority too?
Loss not leader
Once you start digging into this topic – as the EU’s Safefood Knowledge Network asked me to do in an article last year – a number of worrying trends begin to emerge. These raise questions (and concerns) relating to everything from the intensive monoculture practices designed to ensure food is cheap (without often internalising the costs to nature and the environment) to the role genetic modification (GM) and gene editing will play in fighting these pests; and on to self-sufficiency versus globalisation and the threats posed to food security if business continues as usual.
This is a lot to chew over in one article. However, the following should, in honing in on plant pests and diseases, provide ample food for thought as the food sector assesses future risks and looks to build resilience (and what follows is longer than Defra’s public facing 2018 food civil contingencies report).
Globally, 10-16% of harvest (or $220 billion, £174bn) is lost to plant pests every year, according to the Food and Agriculture Organisation (FAO). Meanwhile, research published in Nature Ecology & Evolution in March 2019, showed how the five crops making up around 50% of our calorie intake were being eaten away by pests and pathogens. Wheat: 10-28% losses; rice: 25-41%; maize 20-41%; potato: 8-21%; Soybean: 11-32%.
Now imagine, as researchers did for a paper published in Nature in 2012, that there are severe epidemics across all five of those crops simultaneously: it would leave food sufficient for only 39% of the world’s population. Before you start stockpiling pasta (again), the chances of that happening are pretty low, (as the authors admitted). That doesn’t mean it won’t happen, nor does it mean there won’t be devastating disease outbreaks around the corner. Doomsday can be closer than you think, thanks in no small part to global heating. As Gurr warns: “Pathogens are on the move.”
Mine’s not a flat white
Indeed, climate change is actually promoting the emergence of pathogens on new crops and in new places: plant pathogenic fungi and oomycetes are moving polewards at a speed of 8km a year, according to a 2013 study in Nature Climate Change. This has put both your morning flat white and the livelihoods of hundreds of thousands of producers at risk.
Coffee crops are under threat as leaf rust moves to the mountainous regions in Columbia where previously it was too cool for the fungus to survive. In 2012-13, coffee leaf rust (Hemileia vastatrix) spread quickly through the highlands of Central America, affecting more than 50% of the crop. Some Guatemalan farmers lost up to 85% of their crop, with total losses in the region of $500m (£400m) and nearly 350,000 labourers put out of work, according to a report commissioned by Fairtrade Australia and New Zealand in 2016.
According to World Coffee research, demand for coffee is set to double by 2050, by which time more than half of the world’s suitable coffee land will be pushed into “unsuitability due to climate change. The coffee sector will need up to 180m more bags of coffee in 2050 than we are likely to have,” the institute’s Greg Meenahan told The Guardian.
Closer to home olive oil production has been crushed by Xylella fastidiosa – which the European Commission has called “one of the most dangerous plant bacteria worldwide”. As National Geographic reported last year: “There is no known cure. Once the bacteria infiltrate a host, the plant stays infected until it dies.”
As do the producers’ businesses. The Italian farmers’ association, Coldiretti, warned the government 12 months ago that this could be an “irreversible trend if no action is taken”. As the trees withered on the farms, production of olive oil fell by around 50% (to 185,000 tonnes). Research just published by Wageningen University shows Italian producers could lose more than €5bn (£4.48bn) in the next 50 years, whilst in Spain the losses could be as high as €16.86bn (£15.1bn) if the spread continues and resistant varieties are not planted. And when supply is reduced, prices go up – in the worst case by more than 26%.
The irony, of course, is that a future of devastated harvests and higher prices (not to mention food insecurity and poverty) is, in no small part, due to the desire to drive down costs throughout the chain. At the production end, the world has leaned towards vast monocultures of monogenetically disease resistant crops. Think Robusta and Arabica for coffee, or Cavendish for bananas. These allow for standardised husbandry, transportation and processing but provide the perfect banquet for pests and pathogens.
The FAO calls it the “world’s most important fruit”, and in the UK, 270g of every kilo of fruit we buy is bananas (Kantar Worldpanel, 2017). But it’s under almost constant threat. The arrival of a strain of Fusarium oxysporum (a fungal plant pathogen that causes Panama disease) called Tropical Race 4 (TR4) in South America last year has brought what Professor Gurr referred to as an “almost apocalyptical scenario” that threatens Cavendish, the only variety traded internationally. Climate change has also produced favourable temperatures for spore germination and growth of the fungus Pseudocercospora fijiensis, which causes Black Sigatoka disease and can reduce the fruit in infected banana plants by up to 80%.
So what can be done?
One solution is to stop transporting quite as much food around the world. The globalisation of our food system has brought us variety and choice, but carting food all over the world can result in plant diseases hitching a ride: more than half of all emerging diseases of plants are thought to be spread by introduction. The new Nature Food paper highlights how easily pathogens can proffer in pastures new. “New geographical locations have naive hosts that have not co-evolved with the pathogen, and that do not recognise cues to mount an anti-pathogen response.” And the most common method of rapid pathogen relocation is human activity. “Despite the clear messages of history, humans continue to repeat the same errors and to contribute to global pathogen pollution.”
The Covid-19 crisis has certainly given globalisation – and the just-in-time nature of our food supply chain – a shock. Economists will argue that connectivity is what the world’s agro-industrial complex is all about, but self-sufficiency will gain more traction now than it did three months ago. As Tim Lang, professor of food policy at City University London, points out in his new book Feeding Britain, “long supply chains are open to more risks than shorter ones”.
More research, for example, is needed into the potential of ancient varieties. According to the FAO, there are between 20,000 and 50,000 discovered edible plant species, of which humans regularly consume only 150 to 200. Increased variety will help protect our vulnerable food system and increase intake of vitamins and minerals. Sodexo, for instance, has partnered with Knorr and WWF to encourage people to eat less maize and white rice and more fonio or spelt as part of the Future 50 Foods initiative.
Still, crops will need to be protected, which is why attention will turn again to genetic modification and gene editing. In his first speech as UK Prime Minister, amidst the promises of delivering Brexit and cutting taxes, Boris Johnson threw a bit of a curveball: “… let’s start now to liberate the UK’s extraordinary bioscience sector from anti genetic modification rules.” He was of course referring to the EU’s famously anti-GM stance. Traditional breeding programmes work at a snail’s pace compared to the superfast gene editing techniques in particular, whilst fungicide use is being restricted and the chemicals farmers are left with are currently falling to resistant strains every three to four years (though the weapons they still have at their disposal are pretty powerful according to the insect atlas just published by Heinrich-Böll-Stiftung and Friends of the Earth Europe).
GM is motoring
Concern over chemical use is also increasing amongst consumers. A survey published last week by the NGOs Pesticide Action Network UK (PAN UK) and Sustain found that 71% of people want the UK Government to resist US attempts to overturn bans on pesticides, even if this means the best trade deal cannot be reached. “Much attention has been paid to the dangers of ‘chlorinated chicken’, but the UK public is equally concerned about weakening pesticide protections,” said Josie Cohen, head of policy and campaigns at PAN.
How about GM? A few years ago you couldn’t move for polls gathering data on GM, but few have been done recently. What we can say is that public concern over GM foods has remained pretty consistently around the 20% mark since 2010, according to the Food Standards Agency’s public attitudes tracker. Another poll, in late 2019, found 52% of 1,139 UK consumers would be less likely to consume something if it was GM, with 31% not worried either way. Brexit could well spur more surveys as concerns rise of food standards and safety.
The All-Party Parliamentary Group on Science and Technology has actually tabled an amendment to the Agriculture Bill that would allow the UK to break free from what some believe are restrictive EU rules on gene editing. Asked whether this was a good idea, farming minister Victoria Prentis said last week: “On gene editing, we do not agree with EU rules and we have pushed for many years for the EU to come to the place we are in.”
In that first speech, Johnson referenced potato blight specifically: UK potato farmers spend £60m a year on average trying to keep Phytophthora infestans at bay and, according to The Sainsbury Laboratory, global crop losses from late blight are £3.5 billion annually. “… let’s develop the blight-resistant crops that will feed the world”, the prime minister said.
His focus today is (quite rightly) on resisting another disease, one that he survived but has killed hundreds of thousands of people globally. But as lines are drawn between the Covid-19 crisis and climate change, he can’t afford to forget about the battle to protect crops.