How climate change threatens to make our bread less tasty

Increasing carbon dioxide is impacting some of our favourite foods.

Glenn Fitzgerald, University of Melbourne

Climate change and extreme weather events are already impacting our food, from meat and vegetables, right through to wine. In our series on the Climate and Food, we’re looking at what this means for the food chain.

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The concentration of carbon dioxide in our atmosphere is increasing. Everything else being equal, higher CO₂ levels will increase the yields of major crops such as wheat, barley and pulses. But the trade-off is a hit to the quality and nutritional content of some of our favourite foods.

In our research at the Australian Grains Free Air CO₂ Enrichment (AGFACE) facility, we at Agriculture Victoria and The University of Melbourne are mimicking the CO₂ levels likely to be found in the year 2050. CO₂ levels currently stand at 406 parts per million (PPM) and are expected to rise to 550PPM by 2050. We have found that elevated levels of CO₂ will reduce the concentration of grain protein and micronutrients like zinc and iron, in cereals (pulses are less affected).

The degree to which protein is affected by CO₂ depends on the temperature and available water. In wet years there will be a smaller impact than in drier years. But over nine years of research we have shown that the average decrease in grain protein content is 6% when there is elevated CO₂.

Because a decrease in protein content under elevated CO2 can be more severe in dry conditions, Australia could be particularly affected. Unless ways are found to ameliorate the decrease in protein through plant breeding and agronomy, Australia’s dry conditions may put it at a competitive disadvantage, since grain quality is likely to decrease more than in other parts of the world with more favourable growing conditions.

Increasing carbon dioxide could impact the flour your bread.
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Food quality

There are several different classes of wheat – some are good for making bread, others for noodles etc. The amount of protein is one of the factors that sets some wheat apart from others.

Although a 6% average decrease in grain protein content may not seem large, it could result in a lot of Australian wheat being downgraded. Some regions may be completely unable to grow wheat of high enough quality to make bread.

But the protein reduction in our wheat will become manifest in a number of ways. As many farmers are paid premiums for high protein concentrations, their incomes could suffer. Our exports will also take a hit, as markets prefer high-protein wheat. For consumers, we could see the reduction in bread quality (the best bread flours are high-protein) and nutrition. Loaf volume and texture may be different but it is unclear whether taste will be affected.

The main measure of this is loaf volume and texture, but the degree of decrease is affected by crop variety. A decrease in grain protein concentration is one factor affecting loaf volume, but dough characteristics (such as elasticity) are also degraded by changes in the protein make-up of grain. This alters the composition of glutenin and gliadin proteins which are the predominant proteins in gluten. To maintain bread quality when lower quality flour is used, bakers can add gluten, but if gluten characteristics are changed, this may not achieve the desired dough characteristics for high quality bread. Even if adding extra gluten remedies poor loaf quality, it adds extra expense to the baking process.

Nutrition will also be affected by reduced grain protein, particularly in developing areas with more limited access to food. This is a major food security concern. If grain protein concentration decreases, people with less access to food may need to consume more (at more cost) in order to meet their basic nutritional needs. Reduced micronutrients, notably zinc and iron, could affect health, particularly in Africa. This is being addressed by international efforts biofortification and selection of iron and zinc rich varieties, but it is unknown whether such efforts will be successful as CO₂ levels increase.

Will new breeds of wheat stand up to increasing carbon dioxide?

What can we do about it?

Farmers have always been adaptive and responsive to changes and it is possible management of nitrogen fertilisers could minimise the reduction in grain protein. Research we are conducting shows, however, that adding additional fertiliser has less effect under elevated CO₂ conditions than under current CO₂ levels. There may be fundamental physiological changes and bottlenecks under elevated CO₂ that are not yet well understood.

If management through nitrogen-based fertilisation either cannot, or can only partly, increases grain protein, then we must question whether plant breeding can keep up with the rapid increase in CO₂. Are there traits that are not being considered but that could optimise the positives and reduce the negative impacts?

Selection for high protein wheat varieties often results in a decrease in yield. This relationship is referred to as the yield-protein conundrum. A lot of effort has gone into finding varieties that increase protein while maintaining yields. We have yet to find real success down this path.

A combination of management adaptation and breeding may be able to maintain grain protein while still increasing yields. But, there are unknowns under elevated CO₂such as whether protein make-up is altered, and whether there are limitations in the plant to how protein is manufactured under elevated CO2. We may require active selection and more extensive testing of traits and management practices to understand whether varieties selected now will still respond as expected under future CO₂ conditions.

Finally, to maintain bread quality we should rethink our intentions. Not all wheat needs to be destined for bread. But, for Australia to remain competitive in international markets, plant breeders may need to select varieties with higher grain protein concentrations under elevated CO2 conditions, focusing on varieties that contain the specific gluten protein combinations necessary for a delicious loaf.

Glenn Fitzgerald, Honorary Associate Professor of Agriculture and Food, University of Melbourne

This article was originally published on The Conversation. Read the original article.

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As global food demand rises, climate change is hitting our staple crops

Farmers face falling crop yields and growing food demand.
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Andrew Borrell, The University of Queensland

Climate change and extreme weather events are already impacting our food, from meat and vegetables, right through to wine. In our series on the Climate and Food, we’re looking at what this means for the food chain.

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While increases in population and wealth will lift global demand for food by up to 70% by 2050, agriculture is already feeling the effects of climate change. This is expected to continue in coming decades.

Scientists and farmers will need to act on multiple fronts to counter falling crop yields and feed more people. As with previous agricultural revolutions, we need a new set of plant characteristics to meet the challenge.

When it comes to the staple crops – wheat, rice, maize, soybean, barley and sorghum – research has found changes in rainfall and temperature explain about 30% of the yearly variation in agricultural yields. All six crops responded negatively to increasing temperatures – most likely associated with increases in crop development rates and water stress. In particular, wheat, maize and barley show a negative response to increased temperatures. But, overall, rainfall trends had only minor effects on crop yields in these studies.

Since 1950, average global temperatures have risen by roughly 0.13°C per decade. An even faster rate of roughly 0.2°C of warming per decade is expected over the next few decades.

As temperatures rise, rainfall patterns change. Increased heat also leads to greater evaporation and surface drying, which further intensifies and prolongs droughts.

A warmer atmosphere can also hold more water – about 7% more water vapour for every 1°C increase in temperature. This ultimately results in storms with more intense rainfall. A review of rainfall patterns shows changes in the amount of rainfall everywhere.

Maize yields are predicted to decline with climate change.
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Falling yields

Crop yields around Australia have been hard hit by recent weather. Last year, for instance, the outlook for mungbeans was excellent. But the hot, dry weather has hurt growers. The extreme conditions have reduced average yields from an expected 1-1.5 tonnes per hectare to just 0.1-0.5 tonnes per hectare.

Sorghum and cotton crops fared little better, due to depleted soil water, lack of in-crop rainfall, and extreme heat. Fruit and vegetables, from strawberries to lettuce, were also hit hard.

But the story is larger than this. Globally, production of maize and wheat between 1980 and 2008 was 3.8% and 5.5% below what we would have expected without temperature increases. One model, which combines historical crop production and weather data, projects significant reductions in production of several key African crops. For maize, the predicted decline is as much as 22% by 2050.

Feeding more people in these changing conditions is the challenge before us. It will require crops that are highly adapted to dry and hot environments. The so-called “Green Revolution” of the 1960s and 1970s created plants with short stature and enhanced responsiveness to nitrogen fertilizer.

Now, a new set of plant characteristics is needed to further increase crop yield, by making plants resilient to the challenges of a water-scarce planet.

Developing resilient crops for a highly variable climate

Resilient crops will require significant research and action on multiple fronts – to create adaptation to drought and waterlogging, and tolerance to cold, heat and salinity. Whatever we do, we also need to factor in that agriculture contributes significantly to greenhouse gas emissions (GHGs).

Scientists are meeting this challenge by creating a framework for adapting to climate change. We are identifying favourable combinations of crop varieties (genotypes) and management practices (agronomy) to work together in a complex system.

We can mitigate the effects of some climate variations with good management practices. For example, to tackle drought, we can alter planting dates, fertilizer, irrigation, row spacing, population and cropping systems.

Genotypic solutions can bolster this approach. The challenge is to identify favourable combinations of genotypes (G) and management (M) practices in a variable environment (E). Understanding the interaction between genotypes, management and the environment (GxMxE) is critical to improving grain yield under hot and dry conditions.

Genetic and management solutions can be used to develop climate-resilient crops for highly variable environments in Australia and globally. Sorghum is a great example. It is the dietary staple for over 500 million people in more than 30 countries, making it the world’s fifth-most-important crop for human consumption after rice, wheat, maize and potatoes.

‘Stay-green’ in sorghum is an example of a genetic solution to drought that has been deployed in Australia, India and sub-Saharan Africa. Crops with stay-green maintain greener stems and leaves during drought, resulting in increased stem strength, grain size and yield. This genetic solution can be combined with a management solution (e.g. reduced plant population) to optimise production and food security in highly variable and water-limited environments.

Other projects in India have found that alternate wetting and drying (AWD) irrigation in rice, compared with normal flooded production, can reduce water use by about 32%. And, by maintaining an aerobic environment in the soil, it reduces methane emissions five-fold.

Climate change, water, agriculture and food security form a critical nexus for the 21st century. We need to create and implement practices that will increase yields, while overcoming changing conditions and limiting the emissions from the agricultural sector. There is no room for complacency here.

Andrew Borrell, Associate Professor, Queensland Alliance for Agriculture and Food Innovation, The University of Queensland; Centre Leader, Hermitage Research Facility; College of Experts, Global Change Institute, The University of Queensland

This article was originally published on The Conversation. Read the original article.

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