Climate change and food systems

Tim G. Benton of the University of Leeds and the Royal Institute of International Affairs, Chatham House, addresses the challenges facing food supply chains resulting from the, often unpredictable, impacts of climate change on food systems.

At one level, climate change is simple. It was appreciated in the 19th century, when early experimental studies were carried out, that emissions of some gases, primarily from fossil fuels, would lead to warming via the greenhouse effect. Furthermore, the potential for global warming has been public knowledge for well over a century. For example, a snippet from 1912 in an Australian local newspaper recently came to light^[1]describing how burning coal created carbon dioxide, which ‘tends to make the air a more effective blanket for the earth, and to raise its temperature’.

The article concluded that ‘the effect may be considerable in a few centuries’. One century later, we are finding that already the effect is considerable.

Where climate change is more complex is in understanding exactly how it will affect us and the weather we experience. As we all appreciate, a weather forecast’s accuracy declines over days – as small, random, differences in the real weather diverge from the weather model’s predictions.

Understanding exactly how the weather will play out over decades and what impacts it will have, is a real scientific challenge. Nonetheless, it is one where advances are being made rapidly.

Climate change can affect us, and the food system, in three broad ways:

1 There will be a gradual increase in global temperatures: ‘global warming’

When most people think of climate change, they imagine a gradual increase in global temperatures over decades or longer. For example, the annual mean Central England Temperature (CET) for the first decade of this century is 10.22°C. We are currently on course for the world to be 2.6-3.1 degrees warmer by 2100^[2]. This would imply a CET of approximately 13 degrees. Whilst not an exact analogy, Spain has a climate ~3 degrees warmer than the UK (the 1961-1990 average temperature in Spain was 13.3 degrees)^[3]. What adaptation in crops, management, infrastructure (e.g. water storage) would we need to cope if we experienced a Spanish climate?

Recent analyses^[4]of the effect of changing average climate on yields indicate a mixed picture. Generally, for the next two decades, yields in the temperate zones may increase. This is due to a combination of warmer, longer growing seasons and more carbon dioxide in the atmosphere, which acts as a fertiliser providing more building blocks for plants to turn into sugar by photosynthesis. Whilst CO₂ fertilisation may increase yields, it also reduces the nutritional quality of the food produced, by lowering a range of nutrients, in particular iron, zinc and proteins^[5]. Unlike the more temperate zones, yields in the tropics are likely to decline as extreme heat becomes more common. The proportion of places that are ‘winners’ from climate change decreases in the latter half of the century. The most recent analysis suggests that with each degree of increase in global mean temperatures, the yields of wheat would decline by 6.0%, rice by 3.2%, maize by 7.4%, and soybean by 3.1%.^[6]

2 There may be sudden changes in climate in different places.

The climate experienced in any one place depends on largescale circulation patterns in the atmosphere and oceans. These have the potential to change, causing relatively large-scale shifts in the patterns of weather locally. For example, the Atlantic Meridional Overturning Circulation (AMOC) is a global oceanic conveyor of heat from the tropics to NW Europe, carrying 6-8 degrees of warmth to NW Europe.

Recent evidence shows an unprecedented slowdown in its strength^[7]. If weather models are run many times, in a significant proportion this conveyor slows^[8] or stops (and the proportion of cases where it stops grows with cumulative emissions), such that it is as likely as not to turn off over the next two centuries under high emissions scenarios^[9]. A climate model experiment, where the AMOC was slowed to about one third its current value^[10]suggests European temperatures would plummet with much deeper winters, more storms, shorter growing seasons and a fall in food production. This change in oceanic circulation would also affect the inter-tropical convergence zones, affecting monsoon distributions and creating desertification in Sub-Saharan Africa and drying out the Cerrado. Were such a low probability event to occur, perhaps as much as 20-30% of the world’s agricultural output would be at risk^[11].

Whilst an AMOC-driven high impact change in climatic patterns in large-scale weather patterns is unlikely in the next decades, there is emerging evidence that arctic melting is creating a weakening, and more meandering, northern jet stream^[12]. This impacts the flows of hot and cold air, increases the likelihood of blocking (where conditions persist much longer than usual) and alters storm tracks.

Much of the recent variability in European climate in recent years (e.g. long wet stormy winters associated with an unusual storm track, late spring or early spring, heat waves or wet summers) is associated with changing jet stream patterns^[13]. Such shifts in largescale weather patterns, which have not been extensively studied in relationship to agricultural productivity and water availability, have the potential to impact both global and local food systems.

3 The weather will change

Whilst most studies of the impact of climate change on food supplies have focused on the average climate and yields, the impact of variability in weather has been receiving increased attention^[14]: Patterns of high-impact weather are changing fast on a global basis: heatwaves, droughts, extreme rainfall and high-intensity storms^[15]. A warmer atmosphere has more energy and holds more water, so rainfall and storms can become more intense relative to the past and a hotter atmosphere can generate more heat stress on the ground. In addition, changes in large scale weather patterns can bring new sorts of weather to localities.

Whilst we are only just beginning to ask questions about changing weather and therefore to understand how it may impact, past analyses already indicate that variability in yields is going to increase in future^[16](and this work may underestimate how much). A recent report comparing the next three decades to the last^[17] has suggested that the risk of a very severe disruption in global production has increased by over three-fold. Given that weather is often interconnected across large parts of the world (e.g. by the Jet stream or El Niño), there is emerging evidence of risks affecting multiple bread-basket regions at the same time^[18].

Any food product that falls short on supply relative to demand because of a weather or climate impact is likely to increase in price. Not only does this affect availability, it creates opportunities for food fraud through substitution of cheaper ingredients^[19]. Similarly, climate change can increase contamination risk from a range of sources^[20]. Fluctuating supply and prices suggests an increasing need to concentrate on food safety and authenticity.

Climate change will inevitably also impact on agricultural pests and diseases. Existing problems in an area may become more pronounced because less severe winters will reduce over-winter mortality and early springs and later autumns will allow longer seasons for pest populations to multiply^[21]. Furthermore, changing climate will allow pests and vectors to disperse to new areas (both in changing the ‘climate envelope’ – the envelope of temperature and rainfall within which species can exist – and by changing oceanic and atmospheric currents).

Future distributions of pests and diseases are uncertain for a range of methodological reasons^[22]but current indications are that effects might be significant for many fungi, insects and even nematode worms in the soil. Over 50% of the 65 most common livestock diseases are sensitive to climate^[23]. Of course, climate can affect crops and livestock during production, but also can affect pests in stored product (like beetles and mites) as well as fungi, affecting food spoilage, toxin load and quality.

Climate-risk to the global food system is not simply from production, it also potentially affects distribution via impacting on transport infrastructure and logistics. Significant proportions of total food trade are funnelled through a small number of ‘chokepoints’ (such as the Suez Canal, Straits of Hormuz, Malacca, South China Seas)^[24]: disruption to any such area might have significant impacts on food supplies.

Given that weather is often interconnected across large parts of the world (e.g. by the Jet stream or El Niño), there is emerging evidence of risks affecting multiple breadbasket regions at the same time’

Impacts of climate change on food systems

Climate change is likely to create a downward pressure on yields globally, and at the same time, rising CO₂ may reduce nutritional quality. Reducing yields would require a greater area of land and more water to compensate and achieve a fixed level of demand, but at the same time, sea level rise and reduction in river flows is also affecting the availability of resources. In future, due to the competition for land and water, less may be available, not more. This would potentially drive an increase in both the intensity of agriculture and the price of food.

On top of increasing the pressure on the whole system, through changing patterns of extreme weather, climate change is creating greater exposure to ‘shocks’, locally and globally. This is likely to lead to increasing volatility in production. As our global food system is characterised by long supply chains, extreme weather almost anywhere in the world could affect us. Furthermore, as we are globally inter-connected in complex ways, the impact of events elsewhere can be magnified by market and policy responses to cause indirect impacts^[25]. Many recent analyses indicate the complex causation between events and global prices, including energy policy and price, stocks, financial speculation, transparency and policy responses^[26]– all can be important and interact in complex ways, but production shortfalls generated by weather extremes are often the initial spark that drives the volatility ^[27](Figure 1).

For example, the 2007/8 food price spike was related to the loss of a fraction of a percent in global productivity from the Australian drought, coupled with biofuel policy incentivising farmers out of food production, low stock-to-use levels, low transparency in stocks and an oil price spike. Rice prices rose even though they were not subject to a supply shortfall.

The 2010/11 spike was sparked by Europe’s 2010 exceptional heatwave, extending from Europe to the Ukraine and Western Russia^[28]. In Russia, the heatwave was extreme in both temperature (over 40°C) and duration (from July to mid-August in 2010), creating a shortfall in yields of about a third^[29]. At the same time, the Indus Valley in Pakistan, received unprecedented rainfall creating flooding that disrupted the lives of 20m people^[30]. These two events were causally linked through the more meandering jet-stream created by Arctic warming^[31].

In response to its shortfall in yields, Russia imposed an export ban, which fuelled price rises on the global markets^[32]. Other countries responded in a largely uncoordinated way, each driven by internal politics as well as national self-interests^[33].

Analysis of responses to food prices in the developing world showed that the poor (a) worked harder, (b) ate less, (c) lived more frugally, (d) spent savings and (e) responded politically. People often identified their problems as stemming from collusion between powerful incumbent interests (of politicians and big business) and disregard for the poor^[34]. This politicised response contributed to food-related civil unrest in a number of countries in 2010/11^[35]. In Pakistan, where there were food-related riots in 2010, food price rises were made worse by the economic impacts of the floods.

In the UK, the upturn in global commodity prices influenced food inflation, with approximately a 5-fold increase in food inflation in the latter half of 2010. Analysis of purchases in the 5 years from 2007 to 2011 in the UK indicated that consumers bought 4.2% less food, but paid 12% more for it. The poorest 10% spent 17% more in 2011 than in 2007^[36]. People also traded down to save money by buying cheaper alternatives. However, in extremis, people simply could not afford food. Use of emergency foodbanks increased by half^[37]in 2010.

Both of these food price spikes (2007/8 and 2010/11) had far reaching consequences and as the impacts of climate change are likely to increase in frequency and magnitude, this will drive increased food system volatility both locally and globally. This is likely to result in short term shocks, such as disruptions to supply chains, displacement of vulnerable populations and violent conflicts over food or socially.

Supply chain managers need to work with suppliers to reduce their exposure to risks'

Likely impacts on UK supply chains

As described above, there are a number of key issues for supply chains to the UK. First, as areas wax and wane in production suitability, source areas are likely to need to change in the medium-to-long term.

This is likely to create stress on the ability of supply to match demand. For example, as competition for water and heat stress increasingly undermine Spain’s ability to supply to its markets, other areas need to adapt to supplying the foods that Spain currently produces. Whilst areas like South Africa are often mooted as alternative suppliers, in reality, their water availability and ability to supply the quality (and quantity) demanded by UK consumers is uncertain.

Second, as climate introduces volatility in production, prices and responses, supply chain resilience is threatened – as demonstrated in 2017 with avocados, cucumbers and lettuces. Supply chain managers need to work with suppliers to reduce their exposure to risks (e.g. by better water management, better soil management) and perhaps hedge their bets by having multiple supply chains. Such actions are likely to come at a cost: managing resilience often trades off against absolute efficiency.

Finally, for the UK, we are increasingly seeing jet-stream related climate variability, such that weather usually restricted to one season can occur at any time of the year. This introduces variability in demand – at weekly, seasonal and annual time scales. A ‘barbecue summer’ could last a few days or a few months. Can our supply chains keep up?

Tim G. Benton, School of Biological Sciences, University of Leeds, LS2 9JT, UK and Royal

Institute of International Affairs, Chatham House, London, SW1Y 4LE, UK

Email:T.G.Benton@leeds.ac.ukTel: +44(0) 113 343 2886 Twitter: @timbenton

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