It may seem that nothing could be simpler than toast, but next time I see a slice pop up I’ll also see an emblem of the world’s future. That’s thanks to a UK study exploring the problems surrounding growing enough wheat for flour and other foods as the world warms and has ever more people in it. The issue is especially tangled, Mirjam Röder and her University of Manchester teammates show, as adapting farming for the future will likely increase greenhouse gas emissions, driving further warming. “Climate change and food security are two issues which can’t be decoupled,” Mirjam told me. “The same applies for mitigation and adaptation.”
Mirjam is part of the “Climate change mitigation and adaptation in the UK food system” project, led by Alice Bows-Larkin and backed by Manchester’s Sustainable Consumption Institute. One concern the project reflects is that without adaptation farming will probably be the industry worst hit by climate change, with worldwide productivity falling as temperatures rise. Meanwhile, farming also releases about one-tenth of the greenhouse gases we humans emit overall. “These are largely emissions other than CO2, such as nitrous oxide and methane, mainly occurring from natural processes,” Mirjam said. “They are much harder to reduce and control. Then of course global society is challenged by increasing global food demand. So we face a triad of challenges in the food system: we need to reduce emissions, while food demand is increasing and the sector is impacted by climate change.”
Alice and Mirjam’s team looked at wheat because it makes up almost a third of all cereals grown in the world. “Global wheat demand is projected to increase by about 30% by 2050,” Mirjam. “If we don’t find methods to reduce them, total emissions from producing more wheat will rise.” As well as gases released directly by bacteria and other soil microorganisms, emissions from wheat farming arise from the energy needed to produce nitrogen fertiliser. Whether growing more wheat or dealing with rising temperatures, farmers will need more fertiliser, driving more emissions and therefore further warming.
An uneven field
To loosen this knotty problem a little, the Manchester researchers looked at potential worldwide changes in wheat demand and production. In 2009, the top ten wheat producing countries grew 70% of the world’s total supply. Scientists expect wheat demand to grow most in Africa and Asia, the same places where climate change will make its growth harder or impossible. But there could be good news for producing countries in northern parts of Europe, America and Asia, where higher temperatures could raise yields by up to a quarter. However, Mirjam and her teammates warn, that’s only as long as the increase stays below 2°C and these countries successfully avoid extreme weather like floods and droughts. Overall, mostly because the USA, Russia, Ukraine and Australia can increase production, they estimate the top 10 wheat growers alone could almost meet increased worldwide demand in 2050.
The UK is one of the countries that could benefit from improved wheat yields with climate change, which could in turn help feed the world. In a paper published in the journal Environmental Science and Policy on Monday, Mirjam and Alice’s team examined what this might mean for greenhouse gas emissions. They used a ‘life cycle assessment’ (LCA) to look at total greenhouse gas emissions up to drying and sale of wheat to a commercial purchaser. The researchers included emissions from making all the tools and materials needed, such as fertiliser and machinery, checking their assumptions with people like farmers and wheat industry representatives.
After establishing where wheat’s emissions came from, the scientists could look at what impact increasing UK production in a warmer world would have. Currently, per hectare – an area roughly the size of a sports field – British farmers produce 7.9 tonnes of wheat using fertilisers that contain 188 kg of nitrogen. In a world that warmed 2°C by 2100 that could rise to 9.9 tonnes, but that would need fertilisers containing 250 kg of nitrogen per hectare. In a world that warmed 4°C by 2100, UK production could hit 10.9 tonnes, but would need fertilisers containing 489 kg of nitrogen per hectare.
We must fight and adapt
In the 2°C warmer world, the emission intensity – gas released per tonne of wheat – remains similar to today, though in the 4°C warmer world it increases by half. However, because output is rising, both warmer scenarios increase greenhouse gas emissions from UK wheat farming overall, by a quarter at 2°C and more than doubling at 4°C. That may seem unavoidable, but Mirjam’s team considers broader use of a product already used in horticulture, a more intensive plant-growing industry: nitrification inhibitors. These are chemicals that slow the reactions that produce nitrous oxide, both keeping more nitrogen in the soil, cutting the need for fertiliser, and reducing emissions. And though they’re expensive, they are already available. The Manchester researchers found nitrification inhibitors could cut today’s UK wheat farming emissions and those in the 2°C warmer world by about a fifth.
Mirjam stressed that her group’s work shows how closely adapting to and fighting climate change can be linked, and why it’s important to begin doing both. “Often it seems that decision makers think we can just muddle through the problem for now or invest more on adaptation later on,” she said. “This will become very difficult if we further threaten our basis to produce enough, affordable and good quality food. Some technologies might help to achieve the significant emission reductions needed to avoid dangerous climate change, but we also need to become more aware of the interactions and consequences of our decisions and behaviour. Research from my colleagues at the Tyndall Centre for Climate Change Research at the University of Manchester has shown that behavioural change and responsible use of the things we consume can make a significant contribution to reducing emissions.”
The differences in how countries’ wheat production will change as the world warms will also have broader political implications, Mirjam added. “Many of the regions with rapidly rising food demand will likely be the first to see production become limited by climate change,” she emphasised. “So a great number of countries may rely on a few main producer nations where climate change impacts are less pronounced and where production might be more efficient and less emission intense. This brings up the question of responsibility and justice.”
Röder, M., Thornley, P., Campbell, G., & Bows-Larkin, A. (2014). Emissions associated with meeting the future global wheat demand: A case study of UK production under climate change constraints Environmental Science & Policy, 39, 13-24 DOI: 10.1016/j.envsci.2014.02.002