Rain might seem like good news for cocoa farmers, as the tropical tree needs moisture to grow and produce fruit. However, a new study reveals that rain itself can become the enemy of the crop when it comes in large quantities and at the wrong time, potentially damaging flowers and young fruit and increasing the risk of disease, ultimately leading to reduced yields.
Hot Topics
The human body ages in leaps and bounds Scientists identify two critical ages
From your phone screen to your data How do malicious apps sneak in and steal your secrets?
The findings are particularly significant given that some six million smallholder farmers worldwide rely on cocoa as their primary source of income. Côte d'Ivoire, Ghana, Indonesia, and Ecuador together produce a substantial share of the world's cocoa crop, while West Africa experienced harvest losses of up to 40% in the 2023/2024 season, according to some estimates, raising concerns about the future of cocoa production and chocolate prices.
Anna Leah Albright, a researcher in Harvard University’s Department of Earth and Planetary Sciences and lead author of the study, says the findings shift attention from the usual question about average rainfall or rising temperatures to a more precise question: What happens when heavy rain hits a cacao tree at a sensitive stage of its growth?
To answer this question, the team started from Ghana, the world’s second-largest cocoa producer, using production records across 66 administrative regions from the 2000/2001 season to 2022/2023, and linked them to daily rainfall and temperature data.
The analysis showed that heavy rainfall from April to June, combined with a lack of rainfall during the dry season from November to February, could together explain about 68% of the annual variation in cocoa production in Ghana.
When the rains become heavy, flowers and young fruits can be directly damaged, and the pollination process, which is the transfer of pollen grains until fruit is formed, may be disrupted.
The researcher adds: "There is another, quieter danger: disease." She explains that heavy rains and humidity help spread fungal diseases, most notably "black horn" disease, one of the most serious cocoa diseases in West Africa.
Rain spray can also carry pathogens from the soil or from infected fruit to other parts of the tree, making heavy rain a double threat that directly harms the plant, while simultaneously paving the way for the spread of infection.
Climate predictions
The researchers applied the same approach to data from Ecuador and Indonesia, finding a similar negative correlation between heavy rainfall during the rainy season and cocoa production. In Ecuador, heavy rainfall alone explained up to 52% of the yield variance in one of the rainfall datasets used.
In Sulawesi, Indonesia, the impact was present but weaker, due to the intervention of other factors such as some farmers switching to palm oil and clove cultivation.
The findings open the door to using climate forecasts to protect crops; the study found that extreme rainfall is partly linked to broad climate patterns such as El Niño and changes in Atlantic surface temperature.
Tags:
science
