Hacia una producción sostenible de cacao en África Occidental: un enfoque de modelización múltiple para el apoyo a la toma de decisiones en sistemas agroforestales
Year: 2025
Type: dissertation
Abstract: The future demand for cocoa is projected to increase significantly due to the growing consumption of chocolate and cocoa-derived products, particularly in emerging market. The West African region is the world’s main cocoa producing area, with leading countries including Côte d’Ivoire, Ghana, Cameroon and Nigeria. Cocoa is produced in family-run, mediumsized plantations. Approximately two million households depend on cocoa farming in West Africa. However, the economic problems of cocoa producers are vast, including limited access to credit, low profits and incomes, or the market price volatility. These problems contribute to the low productivity per hectare in this region due to poor farm maintenance practices. This low productivity and the rising demand for cocoa presents considerable challenges in terms of sustainability. As cultivation intensifies to meet market requirements, it often leads to the expansion of agricultural frontiers, exacerbating deforestation and contributing to climate change. Therefore, the conflict between productivity and sustainability in the face of climate change, mitigation and adaptation, as well as the socioeconomic problems requires a multifunctional land use that fulfils the multiple demands of cocoa beans, environmental protection and diversity of incomes for farmers. The inclusion of shade trees in cocoa plantations - agroforestry - is often proposed as an effective strategy to address the above-mentioned productivity and sustainability concerns. The last decades have seen an increase in scientific data on the climate change mitigation and adaptation potential of agroforestry systems. Although results from research and development projects agree that agroforestry is the most suitable way to reach a sustainable cocoa production, the adoption of agroforestry systems also presents its own set of challenges and barriers. For example, most farmers relate the microclimatic conditions generated in cocoa-based agroforestry systems as one of the causes of lower yields compared to monocultures due to the interactions among the components of the agroforestry systems concerning the main crops. Nevertheless, it has been repeatedly emphasized in agroforestry literature that the success of agroforestry relies heavily on the exploitation of component interactions. Therefore, understanding the drivers of cocoa growth and yield in agroforestry systems would enable us to develop effective well-informed management recommendations under a changing climate, support sustainable agricultural practices, and maximize the ecological benefits gained from agroforestry systems. Within this PhD thesis, the potential capacity of agroforestry systems to climatechange mitigation and adaptation potential was evaluated. Furthermore, the effects of biophysical interactions on cocoa growth and yield in agroforestry systems was investigated in a field trial. As an approach, observational data and different modelling techniques were combined to study i) the vulnerability of cocoa-based agroforestry systems to climate change and adaptation capacity, ii) the potential of cocoa-based agroforestry systems to climate change mitigation through carbon sequestration and storage, iii) the biophysical interactions in cocoa-based agroforestry systems and their effects on cocoa growth and yield, and iv) the capacity of terrestrial laser scanning to quantify canopy structural traits in representative agroforestry systems typologies. In Chapter II, different species distribution models were developed to identify shade tree species best adapted to future climatic conditions in West Africa. The models projected an increase of up to 6% of the potential suitable area for cocoa by 2060 compared to its current suitable area in West Africa. Furthermore, the suitable area was highly reduced (14.5%) once considering only available land-use not contributing to deforestation. Regarding shade trees, 50% of the 37 shade tree species modelled will experience a decrease in geographic rate extent by 2040 in West Africa, and 60% by 2060. In Chapter III, a combination of allometric equations and empirical growth models was used to forecast carbon sequestration in cocoa-based agroforestry systems. Results showed that innovative designs can provide relevant carbon sequestration benefits compared to other more traditional cocoa systems. Carbon stock in the trial ranged from 37.2 to 40.5 Mg C ha−1 at 20 years, with abrupt changes due to the management activities during the study period. Timber trees stored more than 45% of aboveground carbon stocks across all agroforestry treatments. In Chapter IV, a structural equation modelling approach was developed to identify the drivers of cocoa growth and yield in agroforestry systems. Model’s outputs showed improved cocoa establishment in certain designs of agroforestry systems compared with monoculture. However, stand characteristics (i.e. increase in the number and height of shade trees) had a negative effect on cocoa yield and growth via changes in cocoa tree morphology. In this sense, cocoa tree morphology was more important than the direct effects of stand characteristics, leaf area index, and soil volumetric water content in controlling cocoa growth and yield in agroforestry systems. In Chapter V, terrestrial laser scanning was used to quantify the 3D distribution of Plant Area Density (i.e. total one-sided total plant surface area within a given volume) and different canopy structural traits (Plant Area Index, light attenuation and transmittance) at different spatial resolutions. Results showed that species composition, rather than planting arrangement, notably influenced the vertical distribution of plant area density and canopy structural traits. Plant area index in the experimental plots ranged from 4.94 m2 m-2 to 22.31 m2 m-2, with these values slightly higher than those reported in tree forest ecosystems. Taken together, the findings within this research project constitute new information which not only furthers our understanding of cocoa production in agroforestry systems but will also aid in developing new guidelines for achieving a sustainable intensification of cocoa systems. This multidisciplinary approach could serve as the foundation for the future development of a Decision Support System (DSS) tailored to cocoa-based agroforestry systems. It would enable producers and managers to identify optimal management practices, evaluate climate change adaptation and mitigation strategies, and maximize the productivity and sustainability of the agroforestry system.
Author: Ariza Salamanca, Antonio Jesús
Language: English
Subfield: Horticulture
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7047587958