Short answers, pulled from the story.
A 2025 systematic review found that without effective adaptation measures, climate change could reduce global agricultural food production by up to 14% by 2050. A 2024 review by Yuan et al. projected that under high-emission scenarios without adaptation, yields of the four staple cereals, maize, rice, wheat, and soybean, could decline by approximately 5-10% by mid-century.
The IPCC Sixth Assessment Report from 2022 projected that by 2050, the number of people at risk of hunger will increase under all scenarios by between 8 and 80 million people. Nearly all of the additional people at risk are expected to be in Sub-Saharan Africa, South Asia, and Central America.
Elevated atmospheric CO2 increases photosynthesis and improves water-use efficiency in C3 plants such as wheat and rice, partially offsetting yield losses from warming. However, a 2016 estimate found that ozone increases alone caused yield losses of 5±1.5% in the four major crops, nearly cancelling the fertilization effect of 6.5±1.0%. CO2 fertilization also has little effect on C4 crops like maize and reduces the nutritional quality of most food crops.
Higher atmospheric CO2 concentrations are projected to reduce protein, iron, and zinc content in common food crops by 3-17% at CO2 levels expected by 2050. Doubling CO2 results in an average 8% decline in mineral concentrations, with lower levels of magnesium, calcium, potassium, iron, and zinc. Some two billion people live in countries where citizens receive more than 60% of their zinc or iron from crops such as wheat, rice, peas, and soybeans.
Maize is considered the most vulnerable of the four major crops; one meta-analysis found that every 1 degree Celsius of global warming reduces maize yields by 7.4%. Under the high-emission SSP5-8.5 scenario, the latest models project a global decline in maize yields of 24% by 2100. Wheat yields could increase under high warming due to precipitation and fertilization effects, while rice projections remain less consistent.
Analysis of historic data has found synchronized climate events already associated with up to 20% yield losses across major growing regions. If every region with a synchronized growing season were to experience simultaneous crop failure, losses to the four major crops could reach 17-34%. One 2021 estimate suggested the high-emission scenario would result in a 4.5-fold increase in the probability of breadbasket failures by 2030, which could increase 25 times by 2050.