Wheat, used in our daily bread, pasta, noodles and pastries, is a crucial ingredient in the human diet. An increasing global population coupled with a changing climate threaten this relationship. Our survival as a species is dependent on fomenting one more scientific revolution in agriculture.
Wheat has been a staple component of the human diet for thousands of years. Around 10,000 years ago, the first hunter-gatherers began cultivating strains of emmer, einkorn and spelt [1]. These ancient wheat grains were the precursors of the wheat varieties we use now. However, they required milling to release their nutritious contents. Grains from modern varieties of wheat are more easily separated simply by threshing.
The domestication of wheat and the transition from hunter-gatherers to farmers was a critical step towards human civilisation. The first wheat farmers could harvest the grains and store them to provide sustenance throughout the year. This cultivation of wheat allowed humans to settle and found agriculture-based civilisations in the Levant. The flour released from the grains could be mixed with water into a paste to form flatbreads. Leavened flatbreads became very popular with the ancient Egyptians [2].
Wheat is so ubiquitous that it now accounts for a fifth of the calories consumed in the World [3]. This was only possible due to the ‘green revolution’ [4]. In the 21st century, improvements were made in: the manufacture of fertilisers; mechanised farming; and plant breeding. These developments led to substantially better crop yields. It is only because of these improved technologies that we can feed a global population of 8.2 billion. It is also used as animal feed and to produce biofuels. We should therefore be concerned about the impact climate change will have on this essential commodity.
The modern wheat varieties currently used by farmers across the globe were developed to maximise yields under different climate and environmental conditions to those predicted in the next 50-100 years. Predictions suggest an increase in global temperature of 1.5°C by 2050 [5]. Increasing temperatures will also likely mean an increased incidence of heatwaves, flooding and other extreme weather events. Coupled with the unsustainable nature of our intensive farming methods, these changes will undoubtedly have a severe impact on crop growth and total produce.
In the UK, winter wheat, triticum aestivum, is the most commonly grown species. It is used primarily to produce flour for bread. Winter wheat is sown into fields during the autumn months to capitalise on the optimal conditions of 0-5°C over the winter. Another important wheat we grow is durum wheat, triticum durum, which makes up about 5% of the global market and is used to make flour for pasta, couscous and noodles. Although these modern varieties have been optimised for their high yields, they have a reduced tolerance to other stresses such as diseases, pests, temperature changes and droughts. Their high yields are also dependent on the intensive application of fertilisers, pesticides and herbicides.
Elevated carbon dioxide levels in the atmosphere should lead to an increase in photosynthetic rate and therefore plant growth, one would expect. However, in experimental conditions when carbon dioxide levels are doubled, changes in important fatty acids are observed, specifically phosphatidylcholine and phosphatidylglycerol [6]. We conclude that changes in carbon dioxide may cause some fatty acids to be preferentially transferred to the membranes of chloroplasts and mitochondria rather than used in the cell membrane, not conducive to crop growth.
Long term studies on wheat cultivation in China have shown regional differences in the impact of changing temperatures and climate [7]. After rice, wheat is the second biggest crop produced in China. Data obtained over 30 years (1992-2020) showed that Henan and Shandong province were more prone to climate change than Hebei province. Average temperatures in China have increased by 0.9°C in those years and annual rainfall has increased by 15.3mm. The more northernly province of Hebei benefitted from increased temperatures, whilst crop yields in southern regions were negatively impacted by the raised temperatures. However, the crop yield in Shandong province improved due to increased rainfall. In general, increased temperatures had the effect of reducing crop yields, whereas increased rainfall improved them, except when rainfall became excessive due to flooding.
In the UK the best yields of wheat are linked to warm night-time temperatures and heavy rainfall during the day during the foundation stages of growth [8], or when maximal temperatures and rainfall were prevalent during the production phase. Even during crop cycles where weather patterns were extreme farmers were able to adapt and still obtain excellent yields. Concerns about future performance will be dependent on whether increased amounts of rainfall become more common during key phases in crop growth.
Our dependence on wheat is a consequence of three scientific revolutions. The first occurred 10,000 years ago and was quite likely accidental. It produced the first bread-wheat, a hybrid of spelt, emmer and einkorn varieties. The second occurred in 17th century Britain when agricultural output fueled a population explosion; the population in England and Wales doubled between 1700 and 1800. The third, the green revolution, occurred in the 21st century when new breeding methods, coupled with advances in inorganic fertilisers, pesticides and mechanised equipment, vastlyimproved crop yields.
To meet the future challenges of a growing global population and a changing environment we need a fourth agricultural revolution. This can only be achieved by using genetically modified crops designed to withstand higher temperatures, resist droughts or tolerate flooding [9]. The wheat genome was finally sequenced in 2018, an effort more challenging than the human genome as wheat contains 6 separate genomes. This advance will enable scientists to better control the complexity in wheat genetics and switch on / off genes that are better adapted to increased temperatures, droughts and flooding events.
Global demand for wheat is expected to double by 2050 from 2005 levels [10]. We may not know what the future may bring but there is comfort in knowing that our species has been here before. Our food security is vital for our survival.
References
1. de Sousa T, Ribeiro M, Sabença C, Igrejas G. (2021). The 10,000-Year Success Story of Wheat! Foods. Sep 8;10(9):2124. doi:10.3390/foods10092124. PMID: 34574233; PMCID: PMC8467621.
2. http://www.historicalcookingproject.com/2014/12/guest-post-ancient-egyptian-bread-by.html
3. Bonjean, A. P. (2016). The saga of wheat–the successful story of wheat and human interaction. The World Wheat Book: A History of Wheat Breeding; Bonjean, A., Angus, W., van Ginkel, M., Eds, 1-90. https://www.bonjean-associes.com/_files/ugd/140b76_b08d8fd4f64b436fa118b4c91a8e2bab.pdf
4. Rao, Madhura (2023). https://www.foodunfolded.com/article/crops-that-feed-the-world-wheat
5. https://scied.ucar.edu/learning-zone/climate-change-impacts/predictions-future-global-climate
6. Edlin, D.A.N., Williams, M and John L. Harwood (1998). Changes in Leaf Lipid Metabolism caused by the Greenhouse effect. Advances in Plant Lipid Research, 514-516.
7. Zhang, H.; Tang, Y.; Chandio, A.A.; Sargani, G.R.; Ankrah Twumasi, M (2022). Measuring the Effects of Climate Change on Wheat Production: Evidence from Northern China. Int. J. Environ. Res. Public Health 2022, 19, 12341. https://doi.org/10.3390/ijerph191912341
8. Slater et al. (2022). Resilience of UK crop yields to compound climate change. Earth System Dynamics. DOI: 10.5194/esd-13-1377-2022. Open access.
9. D. Tilman, C. Balzer, J. Hill, B.L. Befort (2011). Global food demand and the sustainable intensification of agriculture, Proc. Natl. Acad. Sci. U.S.A.108 (50) 20260-20264, https://doi.org/10.1073/pnas.1116437108.
10. Sullivan, J. (2021). The future of eating: how genetically modified food will withstand climate change. https://www.nhm.ac.uk/discover/the-future-of-eating-gm-crops.html
