Our daily bread

What does the future hold for one of our most important food crops? (8 minute read)

Welcome to The Turnstone. Here, I help people understand important issues such as Covid-19, climate change and conservation. I send my articles out every Sunday - if you’d like them emailed to you directly, you can sign up to my mailing list.

When we think about ways people are affected by war, we usually think of direct impacts. We think of the soldiers killed and injured in the fighting, the civilians displaced and traumatised – and, more often than not, targeted despite international law – and the children growing up surrounded by conflict and loss. But Russia’s invasion of Ukraine is harming people far beyond the borders of those two countries. Ukraine is one of the most important exporters of a crucial food crop – wheat. And 95% of those wheat exports go through Black Sea ports such as Odessa and Mariupol.

Millions of tonnes of grain are now stuck in Ukraine, in silos, warehouses and ships. While there are diplomatic efforts being made to find solutions, there’s no easy answer. Moving the grain by land poses major challenges. Ukraine’s railway tracks are a different size from the railway tracks used in the European Union, so cargo needs to be reloaded at the Ukrainian border. That leaves road, which requires a lot of trucks and drivers.

The problem is not just with the current grain crop. Ukraine’s wheat harvest this year is expected to be poor, only two-thirds of the usual, due to the effects of the war. And even though the harvest will be smaller, since grain silos are full there may be nowhere to put this year’s harvest. With nowhere suitable to store the grain, it may end up rotting. Meanwhile, the world grain price is rising, and the most vulnerable are already suffering.

But the problems with wheat are not only confined to Ukraine. India is another major wheat producer, and they had planned to export more to cover some of the shortfall from Ukraine. However, those plans came to a halt a few days ago when India announced it was banning wheat exports, concerned about their own food security. In some of India’s best wheat producing areas, production is likely to be 10-15% less due to the heatwave that has been affecting the country.

Most of the world’s current food security issues are the result of conflict, not weather conditions, but factors such as drought play a role. India’s current heatwave is an event made much more likely by climate change. And that made me wonder, what does climate change mean for the production of wheat?

Wheat is one of humanity’s oldest crops. It has been cultivated for around 10,000 years, with its origin in the Middle East. Wheat appears in the art of the ancient Sumerian civilisation, which thrived in what is now southern Iraq around 4000-6000 years ago. Wild relatives of wheat are distributed from the Balkans to Iran.

Modern wheat has a complicated ancestry. The plant that we mostly think of as wheat is the modern bread wheat, with the scientific name Triticum aestivum. It does not come from a single ancestral species, but combines the parentage of three different species. There are other types of wheat which are less commonly grown as well, such as durum wheat, which is used to make pasta, and spelt, one of the more ancient types which is making a comeback as a specialty crop. The wild ancestors of wheat were carefully bred by generations of early farmers to have larger grains which stayed attached to the stalk when ripe. This latter trait was crucial to the harvest of grain, because if the grain was scattered on the ground as soon as it was ripe, as in wild grasses, it was difficult to harvest.

Wheat is now grown around the world, on every continent except Antarctica and in a wide range of climates. China, India, Russia and the United States are the largest producers, with Canada, Pakistan, Australia and Ukraine among the other major producers. If the European Union was a single country, it would rank ahead of India, and in some years it even produces more than China. However, many countries which you might not expect to grow lots of wheat, like Mexico, Brazil, Morocco, Ethiopia and Bangladesh, produce more than a million tonnes a year each.

Wheat is an annual species, which means it completes its life cycle within a year. Like many plants, it needs to experience certain conditions in order to produce flowers. Most sensitive are the varieties known as winter wheat. These varieties are planted in the autumn and must experience a prolonged period of cold in order to flower, which is important because unless wheat flowers, it won’t produce seed (which is the part we eat). Spring wheat varieties do not require cold temperatures to flower, but are also not tolerant of frost. The other complicating factor in wheat flowering is day length – some varieties of wheat are sensitive to changes in day length, which means different varieties are needed for different latitudes. A variety which produces well in Ukraine could be next to useless in Bangladesh.

Image credit: Melissa Askew on Unsplash

Varieties of wheat also differ in their tolerance of other environmental conditions such as drought and heat stress. Heat stress, in particular, is a problem for wheat, causing a reduction in yield. It doesn’t cope well with temperatures over 35°C, and in some cases can experience heat stress in temperatures over 25°C. But again, it depends very much on the variety which is being grown. Deciding which variety to grow is one of the most critical choices a grower must make.

The variation in different types of wheat, and the many countries in which it is grown, means it’s not a straightforward matter to understand how climate change will affect it. Conditions which could prove disastrous for winter wheat may benefit spring wheat. If one variety proves unsuitable, another could be grown instead. Some areas may become less suitable for wheat, while others may become more suitable.

There’s another complicating factor which needs to be considered before trying to understand the impacts of climate change on wheat, or in fact any plant, and that is the direct effect of increased carbon dioxide. While we are used to hearing about carbon dioxide as a big part of the problem in climate change, it’s also essential for the growth of plants. Through holes which can open and close in the surface of the leaf, called stomata, plants absorb carbon dioxide from the air. The carbon dioxide is used in the process of photosynthesis, where plants make energy from sunlight (the video here explains the process).

The increased carbon dioxide level in the atmosphere has already increased the rate of photosynthesis, and this will continue as the level rises further. Increased carbon dioxide also reduces a plant’s need for water. In order to absorb carbon dioxide, the plant needs to have its stomata open, but while the stomata are open, the plant also loses water. Higher carbon dioxide levels mean that the plant needs to keep its stomata open for a shorter period of time to produce the same amount of energy. So, any assessment of the impact of climate change on wheat needs to take into account the rising productivity and decreased water usage resulting from increased carbon dioxide levels.

All together, it makes for a complicated picture, and it’s no wonder that the answers you get depend very much on which paper you look at and which factors those papers consider. For example, a review from India found that some studies predicted yield increases, while others predicted decreases. Most crucial seems to be whether irrigation is used, with yield increases most often found in irrigated areas.

Studies in the USA and Canada also gave contradictory answers. A USA study on winter wheat, the type which needs prolonged cold temperatures in winter, showed that yields were likely to fall under climate change. In Canada, spring wheat, which is the kind that doesn’t require winter chilling, is expected to show increases in yield. Larger increases were predicted with higher rates of warming, but these predictions were also more uncertain. Outside the scope of the study was predicting whether the regions suitable for growing crops like wheat would themselves change, although this is likely.

At a global level, the picture is just as confusing. Some reports suggest that wheat production will increase, such as this NASA study which found that more land would become suitable for growing it (the study wasn’t all good news, as maize production was expected to fall). Other reports suggest wheat production will decrease, such as this study which suggests wheat-growing areas would suffer increased drought.

To help wheat cope with conditions such as increased heat stress and increased drought, crop scientists are trying to breed new varieties. Some are using more traditional approaches, such as crossing cultivated wheat varieties with wild relatives to introduce more genetic diversity. But others are using techniques which are much newer and unfamiliar to many of us, such as gene editing. That is a topic I will return to, because I don’t feel as if I have a good understanding of the issues, and I’m sure I’m not alone.

It's not clear, then, exactly what is going to happen to wheat production under climate change. It depends on so many factors, that there simply isn’t a single answer to the question. But one thing is clear – the future of wheat very much depends on the success of crop scientists in producing varieties which will grow in the new conditions we face.

The Turnstone is free, but if you would like to support my work with a monthly or annual subscription, click the “Subscribe now” button below for options.

If you would like to support The Turnstone with a one-off contribution, click the “Buy me a coffee” button below.