April 5, 2014: ‘Battles over water and food will erupt within the next 5-10 years as a result of climate change’, World Bank President Dr Jim Yong Kim MD
The publicly recognisable face of climate change comprises heatwaves, severe weather events, receding snow-lines, more mosquitoes and bleached corals. They may be the curtain-raisers; a likely greater threat to human health and physical survival will come from regional food and water shortages. Food yields and water flows are both sensitive to climatic–environmental conditions. Over the past 7000 years, food shortages due to natural climate changes and fluctuations – droughts, drenching rain, the triggering of locust plagues and so on – have been the main killer. Many modelling studies under a range of climate change scenarios indicate that moderate warming may benefit crop yields in mid-to high-latitude regions, but will reduce yields in seasonally dry and low-latitude regions.
To elucidate causal influences and the strength of relationships, both quantitative and qualitative studies are needed. For simpler relationships such as heatwave-related deaths, standard epidemiological research methods are useful. Qualitative research helps us understand and characterise the many indirect and delayed climate–health relationships, often mediated by system disturbance or disruption – e.g. climate-related harvest failure leading to nutrition deficits, impaired child development and childhood deaths (see also probability-based methods in Lloyd et al. 2011), or situations in which weather disasters, displacement or conflict over dwindling key resources affect the psychological profiles of communities. Historical analogue evidence may also be useful.
In principle we produce food to eat, stay healthy and survive. In practice the economic weight of the agricultural sector (including food exportation) mostly eclipses considerations of health and environmental sustainability. Increases in Australia’s and the region’s population size, deregulated trade and consumer expectations all contribute to intensification of our food-producing systems – often environmentally damaging. Rising temperatures, more severe droughts in vulnerable regions, and shifts in rainfall geography and seasonality pose obvious threats to Australia’s agricultural future, perhaps even to food sufficiency in the longer term. Maybe rising public concern over energy use and greenhouse emissions will reorient consumer food preferences and motivate production-system reforms (e.g. reducing high-global-warming-potential methane emissions from livestock production). The known health benefits of seafood, threatened by ocean warming, acidification and shifting currents, should be reinforcing national and international conservation policies; health co-benefits are on offer.
Climate change influences food yields in a myriad ways. Photosynthesis peaks within its ‘just-right’ temperature range, and then declines at higher temperatures; likewise for the influence of rainfall and soil moisture. Extreme weather events, droughts, climate-triggered infestations and infections all reduce yields. Early on, extra CO2 may ‘fertilise’ some types of plants, but experimental field studies indicate that this benefit is annulled by further warming. Meanwhile, other feedbacks occur: for example, a 1oC rise causes soil bacteria to give off twice as much CO2, while reducing the soil’s moisture-retaining capacity; and heavy rainfall accelerates erosion.
Water insecurity casts long shadows over both hygiene and food availability. With warming, evaporation and hence total rainfall increases, but changes occur in the place, season, amount and pattern of rainfall. In parts of southern Australia more of the wheat-nurturing winter rain now falls in the Southern Ocean and less on land than in past decades. The Murray-Darling Basin and its rural communities are at risk. The global expectation is that wet regions will get wetter and dry regions drier; many monsoon systems will shift and weaken. In South Asia the two main water sources for hundreds of millions, the Brahmaputra and Indus rivers, derive one-third of their flow from the annual thaw of the Tibetan glacier, which is losing mass as warming proceeds. The Ganges, Mekong, Yangtze, Yellow and Red rivers, originating on the same plateau, will be affected too. On current trends, ‘water wars’ may arise under pressures from climate change, population growth and the demands of agriculture, industry and cities. There are tensions between India and Pakistan over India’s planned damming of the upper Indus River system, and between China and Laos, Cambodia and Vietnam as China begins damming the Mekong upstream.
Finally, four other points about a hotter and rainfall-disrupted Australia are relevant to adaptation policies:
1. Reduced food yields cause higher food prices, which impinge differentially within the population.
2. Indigenous populations in reserves may face food storage problems and altered wild-foods availability.
3. Water-borne infection risks will increase in warmer water and in water contaminated by flooding.
4. Australia may come under increasing foreign land-acquisition pressure, as elsewhere in the world, as rich and powerful countries and investment combines seek to secure future food and wealth respectively.
Questions to get you thinking
Reference
Lloyd S, RS Kovats and Z Chalabi, 2011. Climate change, crop yields, and malnutrition: development of a model to quantify the impact of climate scenarios on child malnutrition. Environmental Health Perspectives 119(12): 1817–23.
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