Heavy downpours rather than rising temperatures pose the greatest weather risk to global cocoa harvests, according to new research published in the Proceedings of the National Academy of Sciences. Scientists found that intense rain during the wet-season flowering period damages fragile pods and spreads fungal disease, upending prior assumptions about crop failures.
Rainfall Extremes Outrank Heat Stress
Earlier agricultural warnings cautioned that rising temperatures could make parts of the core cocoa belt less suitable for farming, with yields expected to decline once daily highs surpass about 90°F (32°C). However, a research team led by Anna Leah Albright tested heat stress against rainfall data and found that temperature ranked behind precipitation every time
, according to Earth.com reporting.
The crop is the primary source of income for roughly six million smallholder farmers worldwide. Four nations drive the vast majority of global production: Côte d’Ivoire supplies about 40%, Ghana provides about 20%, and Indonesia and Ecuador account for the remainder. In the 2023/2024 season, West Africa lost up to 40% of its harvest following several weaker years. That sharp shortfall triggered the global price increases that began in 2024. For months, industry observers debated the underlying causes without a consensus.
The Vulnerable Flowering Window in Ghana
To untangle those conflicting theories, researchers examined district-level production records supplied by the Ghana Cocoa Board from the 2000/2001 season through 2022/2023. Localized disruptions such as small-scale gold mining or thin soil would damage specific districts while sparing others. Instead, production rose and fell during the exact same years across nearly every district, pointing to a nationwide environmental driver.
In Ghana, cocoa trees experience their peak flowering period and set their first small pods from April through June, which coincides with the wettest stretch of the year. Those specific pods feed into the main harvest running from October into March, generating 70% to 80% of annual production. When violent downpours strike during those crucial weeks, delicate flowers and tiny pods suffer direct physical damage, and pollination processes break down. High humidity and intense rain also facilitate the proliferation of fungal pathogens, most notably black pod disease.
Broader Regional Signals and Ocean Patterns
The vulnerability extends beyond West Africa. Applying the analytical approach to Ecuador and Indonesia revealed a similar negative correlation between wet-season extremes and yields. In Ecuador, heavy rain accounts for up to 52% of the variation in crop output depending on the dataset used. In Indonesia’s Sulawesi island, the signal appeared weaker due to competing land-use shifts toward oil palm and cloves.
These extreme downpours are not random meteorological events. Because these large-scale ocean oscillations can be forecasted one to two years ahead of time, researchers believe agricultural planners may eventually secure advance warning before farmers must take action in the field.
Atmospheric Warming and Farm-Level Interventions
Underlying climate shifts are also amplifying the risk.
Instead, researchers emphasize timing existing interventions more effectively. Well-timed applications of fungicide following severe downpours, alongside ground cover and mulch to prevent rain-splash infection spreading upward from the soil, could help protect the trees once reliable seasonal forecasts become operational.
