Extreme heat threatens food systems, warn UN agencies, PgII

Key Highlights:

• UN agencies FAO and WMO warn that extreme heat is pushing global agrifood systems to the brink, threatening over a billion people's livelihoods and health.
• Heatwaves are becoming more frequent, intense, and prolonged, damaging crops, livestock, fisheries, and forests globally.
• Global warming is accelerating, with 2025 ranking among the three hottest years on record, triggering more frequent and severe weather extremes.
• Marine heatwaves are increasing, depleting oxygen levels and threatening fish stocks; in 2024, 91% of the world’s oceans experienced at least one.
• Every one-degree rise in average global temperatures cuts yields of maize, rice, soya, and wheat by around 6%.

Detailed Insights:

• Extreme heat acts as a risk multiplier, intensifying droughts, wildfires, and pest outbreaks, sharply reducing crop yields when critical temperature thresholds are breached.
• High nighttime temperatures disrupt the rest period of plants, forcing crops to maintain high respiration rates, stunting growth, and leading to pollen sterility in staple crops.
• For livestock, a breached thermal humidity index triggers acute heat stress, manifesting as a 15% to 25% drop in milk production and significant drops in fertility rates in dairy cattle.
• The intensity of extreme heat events is expected to roughly double at 2C of warming and quadruple at 3C, compared to 1.5C.
• The FAO and WMO call for better risk governance and early-warning weather systems to enable farmers and fishers to take preventive action against extreme heat.

Key Concepts Involved:

• Agrifood systems: The complex network of actors, activities, and resources involved in producing, processing, distributing, and consuming food.
• Thermal humidity index: A measure of the combined effect of temperature and humidity on living beings.
• Marine heatwaves: Prolonged periods of unusually high temperatures in the ocean.