The impact of CO2 fertilisation on foliage in West and East Africa

Abstract: Anthropogenic impact on terrestrial ecosystems continues to grow as we further enhance atmospheric Carbon Dioxide (CO₂) concentrations. The changing climatic conditions and direct influence of CO₂ on vegetation has a big impact on ecosystem functions. Such impacts include CO₂ fertilisation, found to be an important driver of the global greening trend. By increasing leaf photosynthesis and enhancing water use efficiency, CO₂ fertilisation stimulates gross primary productivity and increases carbon storage. Isolating this phenomenon from other drivers of plant growth is however difficult. In this thesis I show that CO₂ fertilisation has had a positive influence on semi-arid and arid region in East and West Africa over the period 1982 - 2015. From Earth observations, it was found that the slopes of the relationship between precipitation and maximum fractional foliage, assumed to be a proxy for CO₂ fertilisation, indicated greater production under the same precipitation levels at the end of the study period. It is discussed that this trend will continue in the future unless the response to CO₂ fertilisation reduces, or long-term negative influences on nutrient mineralization occurs. East and West Africa are predicted to become more prone to extensive droughts and higher temperatures under these enhanced CO₂ concentrations, and thus, improving our understanding of the implications of these conditions is becoming ever more important.