In Extreme Heat, the Most Vulnerable Communities are Left in the Lurch

By the end of this century, up to 250 days per year in tropical Africa may be too hot for people to work outside. That also applies to large parts of South Asia and Latin America. In Africa, combined labour supply and productivity will decline by one third if global average temperatures rise three degrees Celsius above pre-industrial levels. 

These are only two of the warnings spelled out in the report „Extreme Heat and Agriculture“. The UN Food and Agriculture Organization (FAO) and the World Meteorological Organization (WMO) jointly released it in April. On 94 pages, they provide an overview of the scientific literature and identify policy imperatives. The impacts of heat „represent a systemic risk to global food security and to the livelihoods of more than 1,23 billion people who rely on agriculture“, according to the foreword. It is signed by Celeste Saulo (WMO) and Qu Dongyu (FAO), the heads of the two multilateral organisations.

The FAO/WMO report focuses on agricultural businesses, so it does not delve deeply into what happens beyond farm gates. However, the authors warn that we must expect serious impacts on food security, global commodity markets and food price inflation. After all, heat waves reduce the productivity of plants, livestock and human beings.

Unless global heating is brought under control, the experts argue, adaptation efforts will prove futile. Farms can adapt to extreme-heat events only to a rather limited extent. Since individual measures typically respond to a single impact, they are likely to be overwhelmed by compounded impacts. Such impacts are considered to be likely.

At the micro level, for example, a heat wave tends to reduce moisture on a field and in its soil. In addition to suffering high temperatures, crops thus also lack water, and that effect further diminishes their development. Reduced plant growth, in turn, constrains the availability and quality of animal feed – precisely when meat and milk production is already in decline because of heat stress. Should heat coincide with drought, moreover, livestock will thirst for water too.

Climate related problems, of course, are particularly tough when impacts ripple through many sectors. According to the authors, individual farms will not be able to adapt on their own. Policymakers must therefore plan public infrastructure well, establishing early warning systems, for example, and ensuring competent advice is available. They must also create an appropriate regulatory environment for things like risk insurance and emergency relief.

Unless the proliferation of ever more extreme-heat events is stopped, all adaptive action will prove useless. The report therefore insists that climate mitigation is as urgent as climate adaptation. By the end of the century, heat stress is expected to cut the value of global meat and milk production from cattle by about 10 % (or $ 40 billion) in a high-emission scenario. The figure drops to 3.5 % in a low-emission scenario. Due to a growing world population, humanity will need more protein-rich food however.

Hard data and reasonable estimates

As is typical of climate science, the report’s meteorological information is quite precise, while the assessment of the consequences is by necessity more speculative. Extreme heat is occurring more frequently, and though the report presents a host of empirical data, no one can tell exactly how different impacts will interact.

In spite of many remaining uncertainties, one thing is obvious: poor rural communities in disadvantaged countries are most at risk. As the report argues, they have hardly contributed to causing the climate crisis, but have the fewest options for adaptation.

Beyond organisms’ comfort zones

Every species thrives in a specific range of temperatures. Plants, animals and humans suffer when temperatures rise above or fall below their comfort zone. When it gets too hot or too cold, they even die, as the joint report points out.

Climate change is a slow process that pushes most world regions towards the upper limits of the temperature ranges that are good for specific species. As a result, extreme heat is breaching those limits with increasing frequency, turning the slow trend of global warming into acute crises. The report warns that the impacts on agriculture are often harsh and sudden.

As a general rule, the yield of most major crop varieties is negatively affected by temperatures above 30 degrees Celsius. The threshold for most livestock species is lower at only 25 degrees. Heat stress stifles a plant’s growth. It similarly makes animals gain less weight and produce less milk. How bad the damage becomes, depends on how long a heat spell lasts and how high the temperatures rise. The longer an organism is exposed to extreme heat, the less able it is to fully recover. To what extent it is exposed to scorching sunlight matters too. When nights stay too hot for an organism to recover, the impacts are worse.

The vulnerability of an organism also depends on its stage of physiological development. When plants are young, in blossom or bearing fruit, the harm increases. Calves and piglets that are born when the heat is great will probably stay small throughout their lives. The incidence of stillbirths increases too.

Heat events also affect fisheries. When an aquatic heat wave strikes, sweet water fish typically cannot escape to cooler regions from their rivers and lakes. Should global average temperatures rise by 3.2 degrees above pre-industrial levels, the study warns, half of the habitats of 36% of the relevant freshwater species will be affected. That would only be the case for 9% if the temperature rise stays limited to two degrees.

Ocean systems are more complex, but their ecological niches are becoming rarer, for example when heat destroys coral reefs. The UN agencies warn that oceanic food chains may be affected, with total animal biomass dwindling and the scope for fishing being reduced drastically. The report does not indicate figures, but warns that research shows the trend progressing three times faster than previously assumed.

Global Trends

Around the world, extreme-heat events are becoming more intense, last longer and extend over increasingly large spaces. However, these events are not all the same. Some trigger flash droughts even when they initially do not coincide with a dry spell. On the other hand, heat can trigger thunderstorms, with lightning strikes sparking wild fires. When heavy rains follow a long and hot dry-spell, erosion is likely to wash away fertile soils.

Making matters worse, some pests – especially insects – thrive in heat conditions. They thus become particularly aggressive at a time when crops and livestock are weakened. Some plants and animals will also prove susceptible to diseases that were uncommon in their region before global warming changed the local environment.

Farm workers’ plight

The FAO/WMO report pays particular attention to how heat affects human beings. Along with heavy sweating, symptoms of heat exhaustion include weakness, muscle spasms and dizziness. For every degree above 20 degrees, labour productivity is said to drop by two to three percent.

As agricultural work is time-sensitive, it is generally quite difficult to avoid heat stress. Repeated exposure to heat can result in long-term health problems such as cardio-vascular diseases. The risks are greater for elderly people, pregnant women and persons suffering chronic conditions.

The scenario is brutal even in rich nations. In the USA, for instance, agricultural workers are 35 times more likely to die from occupational heat exposure than other workers, according to the FAO/WMO document. For several reasons, things tend to be particularly bad in developing countries:

• Heat occurs more often in tropical and subtropical countries, where the percentage of people working in agriculture is high and poverty compounds health risks.
• Intensive manual labour is especially common in the same world regions, and occupational safety is typically not paid much attention.
• Due to piece-rate payment systems, moreover, workers often neither take sufficient breaks nor drink enough water. Compounding the problems, there is commonly very little shade.

Adaptation dilemmas

Rural communities have been adapting to climate change in various ways. Unfortunately, not all are sustainable. The UN agencies reckon that, from 1992 to 2020, some 88 million hectares in 110 countries were converted from forest to agricultural land because of crop-yield loss and other heat-related impacts. Deforestation at that scale caused the release of almost 22 billion tons of CO2. The former woodlands had a cooling effect, moreover, and stored water. All of the beneficial ecosystem services were lost. The FAO/WMO report insists that climate adaptation and mitigation must mutually reinforce one another.

At the farm level, the experts see various options for adapting to heat events. Biological options include breeding more resilient crops or switching the business model to other plants or animals. Subsistence farmers who rely on their own resources and do not buy inputs cannot do so. For commercial farms, on the other hand, a serious challenge is that high-yielding varieties tend to be particularly vulnerable, so impacts of heat stress are likely to be harsh.

Farm infrastructure matters too, but smallholders will typically not be able to make major investments. Irrigation, for example, can help, though it is likely to prove useless in times of severe drought. The cooling of stables can safeguard animal productivity. The snag is that it requires energy and may thus neutralise climate mitigation. On pastures, simple structures that provide shade can offer relief to animals.

Knowledge-based responses require accurate information from early warning systems, for instance. As farmers cannot collect all the information they need for prudent decision making themselves, however, they depend on public or private services.

Adaptation measures cost money, and some are very expensive. The FAO/WMO report therefore emphasises the relevance of financial services, which are often lacking in the remote areas of developing countries. Far too often, farmers do not get access to credit or risk insurance at all. To grasp opportunities, moreover, farming families need education, which cannot be taken for granted in disadvantaged regions.

Politics matter

The FAO/WMO report therefore concludes that governance is essential. Policymakers must consider more than only what happens on farms. After all, the impacts of extreme heat are likely to ripple through supply chains, affecting not only food security, but public health and political stability too.

The challenges are huge: On the one hand, policies must be tailored to local conditions, which means that stakeholders at the grass-roots level must be involved in planning and decision making. On the other, global affairs matter very much in terms of finance, institutions, science, technology and climate mitigation.

As the multilateral document acknowledges, governance systems tend to be weak in many developing countries. This phenomenon reduces policymakers’ scope for effective interventions at both local and international levels. The implication is stark: poor farmers in disadvantaged areas are likely to be left in the lurch.

Dr.Hans Dembowski is a freelance journalist. Until 2024 he was editor-in-chief of „Entwicklung und Zusammenarbeit“ / “Development and Cooperation“