As the world continues to warm, experts call for a transformation of our food system, moving away from monocultures, diversifying crop systems and reducing reliance on chemical inputs. Anthony King reports
‘Our food system held up a lot better than many thought it would,’ says Hope Michelson, an agricultural economist at the University of Illinois Urbana-Champaign, US, referring to global production and food prices during the Covid-19 pandemic. Yet there remain serious concerns about how we produce food. Especially in light of the 2021 sixth assessment from the Intergovernmental Panel on Climate Change (IPCC), which noted that each of the past four decades has been successively warmer than any decade since 1850 – future crops will face more challenging conditions as our climate warms.
‘Over the past 50 years, we’ve tripled crop production,’ notes Frank Sperling, senior project manager with the International Institute for Applied Systems Analysis (IIASA). Starting in the 1960s, cereals were grown in monocultures that were easier to sow and harvest with large machinery – while agrochemicals were liberally applied. However, this strategy has left us vulnerable.
‘Crop production is industrial in scale and has worked well because of all the fertilisers and chemicals used to protect the crops,’ says plant scientist Christine Foyer at the University of Birmingham. ‘The system still generates good yields, but the way we farm is incredibly polluting and unsustainable.’ Enormous additions of fertiliser are par for the course, she points out. ‘We are going to run out of nitrogen and phosphate fertiliser.’ Additionally, making nitrogen fertiliser consumes 2% of global energy, while nitrogen run off into waterways causes big pollution problems.
Another issue is the vulnerability of single crop fields to disease and predators. ‘If you’re pushed to produce really high yields of monoculture crops, your only option is often to apply chemicals,’ says bee biologist Mark Brown at Royal Holloway, University of London. ‘It is easy for people to blame farmers, but it is incumbent on governments to support farmers to farm more sustainably.’ Agrichemicals are implicated in a marked decline in pollinators and other insects, and the way we grow crops is linked to broader biodiversity loss. ‘Food and agricultural systems are a major driver of environmental change, with 23% of greenhouse gas emissions from agriculture, forestry and other land use activities,’ notes Sperling. ‘We need to think how we can deliver on the nutritional challenges, while correcting for these [environmental impacts].’
From a nutritional perspective too, agriculture is falling short. ‘People are suffering from hunger, while at the same time there is an obesity crisis,’ observes Sperling. A Food and Agricultural Organization study suggests that 3bn people cannot afford a healthy diet. Globally, between 720m and 811m people faced hunger in 2020, which taking the middle range, is around 118m more than in 2019.
We are ‘at the tipping point of a crisis’, warned Ismahane Elouafi, chief scientist at the FAO, speaking at the AAAS meeting in February 2021. ‘Many contemporary agri-food systems are unsustainable and dysfunctional. The global emergencies of climate change, biodiversity loss, pollution and the Covid-19 health crisis all increased the risk and vulnerability of these systems.’
Averaged over the next 20 years, the IPCC report found global temperature is expected to hit or exceed 1.5°C of warming. More intense rainfall and flooding are predicted. Some see signs of this already. ‘In Massachusetts, we normally get three or four inches of rainfall in July. This year we had about 30,’ says Stephen Herbert, an agronomist at the University of Massachusetts, US. ‘Some sections of crops were flooded, and the crop almost died in the field.’ Meanwhile, California is suffering from a severe drought.
There are a variety of solutions. Supplementary irrigation can control drought by providing water and serve as a sink during heavy rainfall. Michelson has studied the use of canals for this purpose in Benin, where it can attenuate reductions in yield. ‘This technology is like an insurance product,’ she says. Meanwhile, intercropping mixes crop species together and is still used in parts of the world, such as in Latin America where maize is often grown with beans. Mixing crops can deliver greater yields, reduce the risk of crop failure and require fewer pesticides. Maize and cereal grains planted in strips deliver more than monocultures, partly because of greater access to light along the borders between the rows, for example (Adv. Agronomy, 2020, 162, 199).
In Kenya, potato is the second most important crop (after maize). Only 5% of the crop is intercropped, with plants such as lima bean, garden pea, chickpea or lucerne, mostly nitrogen-fixing legumes. ‘Including legumes with potato increases nutritive value produced per unit area, contributing to improved human nutrition,’ explains Monica Parker, senior scientist at the International Potato Centre in Nairobi. ‘Intercropping systems adapt potato production to extreme conditions such as exacerbated soil erosion rates in the highlands, high temperatures and heat stress in the lowlands,’ adds colleague Shadrack Nyawade. It also boosts potato yields and improves soil fertility.
Mixing crops reduces pressure from pests and diseases, meaning fewer agrichemicals, boosting natural predators. Drones and robots, together with AI, can also identify pest or disease outbreaks, and selectively apply agrochemicals. ‘Agricultural technologies using real time data from remote sensing or drones could really minimise inputs, for example, putting fertilisers only where needed,’ says Elouafi. Some farmers already fly surveillance drones to measure the precise nitrogen requirements of a growing crop.
If you’re pushed to produce really high yields of monoculture crops, your only option is often to apply chemicals. It is very easy for people to blame farmers, but it is incumbent on governments to support farmers to farm more sustainably.
Mark Brown Royal Holloway, University of London
Another hangover from the past agri revolution is an extreme focus on a handful of crops. Elouafi notes that 125 crops are traded globally, yet historically 6000 plant species were cultivated for foods. Just nine crops account for 66% of total crop production today. ‘We are restricting ourselves by not looking at the full potential of the plant species on Earth,’ says Elouafi. Foyer agrees, noting: ‘A lot of our food industry is based around just five major crops.’
Many traditional species were pushed aside in developing countries to plant staples such as maize. ‘We need to bring back some of these crops that are very nutritious,’ explains Elouafi. Examples consumed locally in African countries include millet, teff and sorghum, and quinoa in the Andes region of South America. Teff grains, for example, contain almost five times more iron than wheat. It is a hardy traditional crop that does better in drought conditions than maize and is more resistant to water logging.
We lost traditional food crops in order to increase productivity of cereals, says Elouafi. ‘We need to bring back neglected species to get a healthier diet and a more diverse food basket.’ Sometimes, commercially viable species are no longer grown. A species of coffee rediscovered in the forests of West Africa by a team of botanists had been grown commercially in the early 20th century but is no longer cultivated. Yet is better suited to warming climate conditions than the two commercial coffee plants (C&I, 2021, 85(5), 6).InnoFoodAfrica is an EU funded project looking at climate-smart African crops to improve cropping practices and processes to turn them into products for urban African consumers and for export. It focuses on crops such as sorghum, teff, millet, amaranth, faba bean and cowpea. ‘These crops have excellent nutritional value, but they are underutilised due to technological challenges in the preparation of food products and acceptable quality for urban consumers,’ explains project coordinator Raija Lantto at the VTT research institute in Finland.
Another global strategy is to improve perennial cereal varieties so they can better compete with annuals, such wheat, barley and rye. Wheatgrass, Thinopyrum intermedium, is a perennial relative of wheat that Danish geneticists are working on to boost its yields and promote as an alternative to barley (C&I, 2021, 85(6), 6). Longer lived cereals have deeper roots to store carbon and take up available nitrogen from soil, and do not require a field to be tilled each year. Their deep roots are more water efficient, especially compared to the water-squandering shallow roots of young cereal plants.
Crops are traded globally, yet historically 6000 plant species were cultivated for foods. Just nine crops account for 66% of total crop production today.
Globally, between 720m and 811m people faced hunger in 2020, which taking the middle range, is around 118m more than in 2019. A Food and Agricultural Organization study suggests that 3bn people cannot afford a healthy diet.
Intercropping mixes crop species together and is still used in parts of the world, such as in Latin America where maize is often grown with beans. Mixing crops can deliver greater yields, reduce the risk of crop failure and require fewer pesticides.
Traditional plant breeding takes from 10 to 15 years, but the need to improve crop varieties is urgent.
Increased climate variability is expected to hit wheat production hard. ‘It doesn’t matter how much good growth you get in a cereal, if your crop is suddenly hit by a heat wave during flower,’ explains Foyer. A few days of hot weather during seed setting can devastate yields. Crop scientists are therefore trying to develop more resilient cereals, for example, by modifying the expression of wheat genes involved in stress response and by direct selection of plants under a range of stress scenarios (Theoret. & App. Gen., 2021, 134, 1753). Unfortunately, traditional plant breeding takes from 10 to 15 years, but the need to improve crop varieties is urgent. ‘It is an issue now of how to speed up the development of new crops,’ says Foyer.
One option is gene editing. While much of the world explores the potential of this new biotechnology, the EU has placed gene editing into the same category as genetically modified organisms (GMOs), setting up insurmountable regulatory hurdles. But gene editing has many advocates. ‘I see it as a breakthrough technology that will allow us to do much more breeding in a more cost-effective way, that will allow us to develop varieties that are much more abiotic stress tolerant, which is very difficult to improve,’ says Elouafi, abiotic meaning non-biological stresses. The European view on gene editing is mistaken, she adds.
Gene editing has set its sights on generating less-demanding varieties. Chinese researchers, for example, are developing wheat lines to better tolerate nitrogen deficiency and boost grain yield (J. Int. Plant Biol., doi: 10.1111/jipb.13151). Plant geneticists in Sweden, meanwhile, have used gene editing to knock out susceptibility genes and increase resistance in potatoes to late blight (Sci. Rep., doi: 10.1038/s41598-021-83972-w). ‘With our genetic know-how and the various “omics” technologies, we are able to reduce the cost of breeding,’ says Elouafi.
There is optimism in the UK around gene editing. ‘Many people think the law will change [in Europe and in the UK] and gene editing won’t be viewed as GMOs, and that will accelerate the development of better crop varieties,’ notes Foyer. But she warns that almost all eggs in the UK have gone into this one basket, which has left it waiting for a major shift in gene editing regulations. She worries about a lack of resources for traditional plant breeding, an expensive endeavour that takes time. Wheat in particular – with its complicated genetics – is a tricky crop to breed using conventional techniques. The UK government needs to spend more on breeding crop varieties that are more sustainable, require less pesticide inputs and tolerate future climate challenges, says Foyer.
Another positive step would be to reduce polluting meat production. ‘If we could reduce the number of animals eating corn in feedlots, we would have more land for available for other foods,’ says Stephen Herbert, an agronomist at the University of Massachusetts, US. He is concerned too about cropland conversion for other purposes, including for solar power, and has experimented with growing vegetables below solar panels.
The 2020 EAT-Lancet report reviewed what a healthy diet from a sustainable food system looks like. It estimated that global consumption of fruits, vegetables, nuts and legumes will have to double by 2050, and foods such as red meat and sugar will have to be cut by more than half. ‘A diet rich in plant-based foods and with fewer animal source foods confers both improved health and environmental benefits,’ the report concluded. It proposes boundaries for global food production to decrease the risk of ‘catastrophic shifts in the Earth system,’ in terms of nitrogen and phosphorus applications, water and cropland use. One analysis suggested that the diet was not affordable for the world’s poor (Lancet Global Health, doi: 10.1016/S2214-109X(19)30502-9).
The EAT-Lancet diet requires radical changes to global agriculture, said Pedro Sanchez, a food security lecturer at the University of Florida, US, also speaking at the AAAS meeting earlier in 2021. He estimated an extra 448m ha of nutrient-rich crops needs to replace other crops, but dietary changes – especially less meat – would free up hundreds of millions of hectares from nutrient-poor crops (Food Security, 2020, 91, 101843). ‘The reason why we cannot afford these good diets is there is not enough supply of nutrient rich food,’ says Sanchez.
Newer technologies could usher in smarter farming and quicker crop breeding, says Elouafi. ‘Lots of breakthroughs should allow us to have a technological solution to push for more intercropping, as well as a broader and diversified cropping system.’ There can be few more pressing issues than the production of enough healthy food for the planet, sustainably and without wrecking the environment for future generations.