A new study based on detailed field measurements in West Africa shows cocoa agroforestry to be less drought resilient than previously thought. The strong El Niño event of 2015/2016 having brought hot winds with temperatures of up to 44 ˚Celsius and severe water limitations almost wiped out the cocoa plants in agroforestry systems.
The findings call for a rethinking of the climate adaptation options in the most important cocoa production region of the world, the scientists say.
The study was conducted by doctoral student Issaka Abdulai of the Tropical Plant Production and Agricultural Systems Modelling (TROPAGS) division of the University of Göttingen, Germany. It was published in the scientific journal Global Change Biology.
West African countries severely threatened by droughts
Over 70 per cent of the world cocoa supply comes from West Africa, a region known to be vulnerable to climatic change and experiencing more frequent agro-climatic extremes in recent years. El Niño events affect the region and have occasionally resulted in severe and long-lasting droughts with considerable yield penalties for cocoa, which is very sensitive to water deficits. In West Africa and elsewhere, cocoa-agroforestry systems often have been promoted as a silver bullet for sustainable farming, both generally and regarding their modification of the micro-climate as an adaptation strategy to prevailing climate risks.
Abdulai assessed the resilience of cocoa plants under agroforestry and full sun systems to drought. He conducted experiments using sophisticated sapflow, micro-climate and soil water measurement techniques. “The study demonstrates that in extreme drought situations, cocoa under full sun appears to be more climate-resilient than systems with shade trees,” says Abdulai. Soil water competition under agroforestry was identified to override the benefits of micro-climate moderation by shade trees during the extreme drought periods.
The agroforestry systems recorded complete cocoa plant mortality while those under full sun survived and recovered. “Under extreme climate conditions with severe droughts, the role of the widely grown shade trees on cocoa plants became critical as competition for soil water with cocoa plants had been intensified,” explains Professor Reimund P. Rötter, Head of TROPAGS division and supervisor of Abdulai.
The study was conducted within the project “Trade-offs and synergies in climate change adaptation and mitigation in coffee and cocoa systems in Ghana and Uganda,” which was funded by the German Federal Ministry for Economic Cooperation and Development.
Abdulai, I. et al. Cocoa agroforestry is less resilient to sub-optimal and extreme climate than cocoa in full sun. Global Change Biology. Doi:10.1111/gcb.13885