Extreme heat threatens global food systems, UN agencies warn

Why in the News?

A new joint report released for Earth Day 2026 by the Food and Agriculture Organization (FAO) and the World Meteorological Organization (WMO) confirms that extreme heat has become a “systemic risk multiplier” pushing global agri-food systems to the brink. The report, titled “Extreme Heat and Agriculture,” warns that these conditions now threaten the livelihoods and health of over one billion people.

How is extreme heat reshaping global agri-food systems?

Critical physiological limits are already being breached in major global breadbaskets: 

1. Thermal stress thresholds: Exceeding critical temperature levels triggers crop failure, reduced yields, and ecosystem imbalance.
   1. Major Crops: Yields for staples like wheat, potatoes, and barley begin a sharp decline once temperatures exceed 30 degree celsius
   2. Livestock: Physiological stress starts at 25 degree celsius. Pigs and poultry are most vulnerable because they cannot sweat, leading to reduced dairy yields, growth issues, and mortality.
2. System disruption: Alters crop cycles, fish migration, and forest productivity.
   1. Compound Hazards: Heat accelerates “flash droughts,” intensifies wildfires, and fosters the rapid spread of pests and diseases, such as locust swarms.
   2. Fisheries and Oceans: In 2024, 91% of the world’s oceans experienced at least one marine heatwave. This depletes oxygen levels, causing cardiac failure in fish and leading to economic losses in fisheries valued at over 6 billion.
   3. Forestry and Ecosystems: Extreme heat disrupts photosynthesis and has suppressed forest productivity by up to 50% in some regions. 
3. Livelihood impact: Threatens over 1 billion people dependent on agriculture and allied sectors.
   1. Labour Loss: Heat already causes the loss of roughly 500 billion working hours annually.
   2. Unsafe Working Conditions: In regions like South Asia and sub-Saharan Africa, the number of days “too hot to work” could rise to 250 per year.
   3. Economic Vulnerability: Poor households lose an average of 5% of their annual income to heat stress, with female-headed households in rural low-income countries suffering losses up to 8%. 

What are the impacts on crop production and food security?

1. Yield reduction: The 6 percent rule: Each 1°C temperature rise reduces maize, rice, soy, and wheat yields by ~6%. 
2. Economic Toll: In low-income countries alone, heat stress causes an average annual loss of $37 billion in crop production.
3. Photosynthesis disruption: Heat doesn’t just stop growth; it forces plants to burn through their own energy:
   1. Night-time Stress: High night temperatures are particularly damaging because they increase respiration rates. Instead of storing energy for grain production, the plant consumes its carbon reserves just to survive the night.
   2. Energy Depletion: This metabolic imbalance leads to stunted plants and significantly smaller, less nutritious grains and fruits.
4. Reproductive failure: Extreme heat acts as a “biological kill switch” during the most sensitive stage of a plant’s life: flowering.
   1. Pollen Sterility: In crops like rice and maize, temperatures exceeding critical thresholds during flowering cause pollen to dry out or become sterile.
   2. Empty Husks: This leads to a phenomenon known as “blanking” or “blindness,” where the plant appears healthy but produces empty husks or pods because fertilization never occurred. Even a few hours of extreme heat at the wrong time can wipe out an entire season’s potential.
5. Compounding Food Security Risks: These biological failures create a domino effect on global food stability:
   1. Nutritional Insecurity: Beyond volume, heat stress reduces the protein and micronutrient content in staples like wheat and rice.
   2. Price Volatility: As major “breadbasket” regions hit these thermal ceilings simultaneously, global markets face supply shocks and rapid food price inflation.

How does extreme heat affect livestock productivity?

1. Heat stress: Triggered by high thermal humidity index levels.
2. Milk production decline: Drops by up to 15-25% in dairy cattle.
3. Fertility reduction: Significant decrease in reproductive efficiency.
   1. Reduced Conception: High Temperature Humidity Index (THI) levels lead to poor estrus expression and hormonal imbalances, with conception rates dropping to nearly 0% in severe conditions.
   2. Embryonic Mortality: Heat causes direct damage to developing embryos and oocytes, leading to higher rates of early embryonic loss and smaller, weaker offspring.
   3. Male Fertility: Spikes in temperature cause sperm deformity and reduced motility, sometimes resulting in temporary or permanent infertility in bulls and boars. 
4. Poultry mortality: The report warns of an escalation in “mass mortality events”. Extreme temperature spikes cause mass deaths in farms lacking climate control.
5. Disease and Immune Suppression: Heat stress compromises the immune system, making livestock more susceptible to existing and emerging pathogens. Altered temperature patterns also expand the range of disease-carrying vectors, such as those responsible for Foot and Mouth disease.

Why are marine ecosystems increasingly vulnerable?

1. Marine heatwaves: Marine heatwaves (MHWs) are now more frequent, longer-lasting, and more intense. By 2024, nearly the entire global ocean surface was impacted, compared to only 60% in 2021.
   1. Systemic Exposure: These events are no longer restricted to surface waters; they are reaching depths of 30-50 metres and even the seafloor, leaving sedentary species like coral and kelp with no “thermal refuge
2. Ocean stress: 91% of oceans experienced at least one marine heatwave in 2024.
3. Oxygen depletion: Reduces fish survival and productivity.
   1. Deoxygenation: Warmer water holds less dissolved oxygen. This creates hypoxic (low-oxygen) conditions that can lead to cardiac failure and mass mortality in fish populations.
   2. Metabolic Strain: Heat increases the metabolic rates of marine animals, meaning they require more food to survive exactly when their food supply, like plankton, is being disrupted by the same heat stress. 
4. Fish stock decline: Around 15% of global fisheries have already been significantly impacted by extreme heat incidents.
5. Disruption of Foundation Species
   1. Ecosystem Collapse: MHWs are “biological wildfires” that decimate foundation species such as coral reefs, kelp forests, and seagrass meadows.
   2. Habitat Loss: The loss of these “nurseries” triggers a domino effect, stripping away the shelter and food sources for thousands of other species.

How does extreme heat act as a risk multiplier?

The FAO and WMO joint report defines extreme heat as a “risk multiplier” because it does not just act alone; it creates a domino effect by magnifying existing vulnerabilities and triggering compound climate hazards. 

1. Drought intensification: Reduces water availability for crops.
   1. Evaporative Stress: Heat-driven evaporation significantly reduces irrigation capacity. For example, a 2025 heat event in Kyrgyzstan saw temperatures 10 degree celsius above normal, which slashed irrigation and contributed to a 25% decline in cereal harvests.
   2. Case Study: In Brazil (2023-2024), extreme heat combined with drought cut soybean yields by up to 20%.
2. Wildfires escalation: There is a direct, strong correlation between heatwaves and more catastrophic fire seasons:
   1. Vegetation Drying: Prolonged heat dries out forests and rangelands, turning them into highly combustible fuel.
   2. Case Study: Portugal’s 2017 fire season, driven by extreme heat, burned a record 540,000 hectares and caused over 1.2 billion in losses.
   3. Carbon Feedback: Wildfires triggered by heat turn natural carbon sinks (forests) into net carbon sources, accelerating global warming further. 
3. Pest outbreaks:
   1. Increased Survival: Warm winters and extreme summer heat often increase the survival and reproduction rates of pests.
   2. Pest Migrations: Heatwaves have been specifically linked to sudden outbreaks, such as locust swarms in Central Asia following thermal shocks to crops.
4. Combined impact: Amplifies food insecurity risks across regions.
   1. Cascading Failures: A single heat event can simultaneously wither crops, kill livestock, dry forests, and make it fatal for agricultural labourers to work outdoors, who may face up to 250 “unworkable” days per year in South Asia and sub-Saharan Africa.
   2. Market Volatility: By triggering simultaneous failures across different sectors (crops, fisheries, and forests), extreme heat overwhelms local economies and drives global food price spikes. 

Why are current policy responses inadequate?

1. Fragmented governance: Lack of integrated climate-agriculture strategies.
2. Insufficient early warning systems: Limits preparedness for farmers and fishers.
3. The “Relief vs. Resilience” Trap: Most funding is currently locked into a reactive cycle:
   1. Post-Disaster Focus: Significant resources are spent on emergency food aid and disaster relief after a crop failure has already occurred.
   2. Underinvestment in Prevention: There is a chronic lack of funding for long-term adaptation, such as developing heat-tolerant seed varieties, building sustainable irrigation, or establishing heat-indexed insurance that pays out before the crop dies.

What solutions are suggested for mitigation and adaptation?

1. Risk governance: Strengthens institutional response frameworks.
   1. National Heat Action Plans: Moving beyond urban areas to include specific agricultural protocols.
2. Early warning systems: Enables preventive action for climate shocks.
   1. The Last Mile: Using SMS, radio, and local cooperatives to deliver hyper-local forecasts.
3. Climate-resilient agriculture: Promotes heat-resistant crop varieties.
   1. Adaptive Breeding: Investing in “orphan crops” (like millets or sorghum) that are naturally heat-tolerant and developing new varieties of staples that can survive temperatures above 30 degree celsius
   2. Nature-Based Solutions: Expanding agroforestry (planting trees among crops) to create micro-climates that reduce ambient temperatures by several degrees.
   3. Livestock Management: Retrofitting farms with solar-powered ventilation and shifting grazing cycles to cooler night-time hours.
4. Technological and financial integration: Supports forecasting and adaptive farming.
   1. Digital Twins: Using satellite data to create digital models of farms to predict where “flash droughts” are most likely to hit.
   2. Anticipatory Finance: Expanding weather-indexed insurance. These programs trigger automatic cash payouts to farmers as soon as a temperature threshold is crossed, providing the liquidity needed to buy extra water or cooling equipment before the crop fails.

Conclusion

Extreme heat is transitioning from an environmental issue to a systemic economic and food security crisis. Addressing it requires integrated climate governance, technological intervention, and proactive adaptation strategies.

PYQ Relevance

[UPSC 2017] Climate Change’ is a global problem. How will India be affected by climate change? How Himalayan and coastal states of India are affected by climate change?

Linkage: The PYQ directly connects to climate-induced extreme heat impacts on agriculture, livestock, and fisheries, central to the article. It provides contemporary data (yield loss, marine heatwaves, heat stress) to enrich answers on regional vulnerability (Himalayan, coastal, agrarian systems).