Space-time variation of vegetation productivity in relation to contemporary and future climates in Africa: a multivariate analysis approach

Abstract

Africa’s vegetation systems are disturbed by climate variability and change. With future climate projected to get warmer, climate effects on vegetation productivity will likely worsen. While many studies have addressed this issue, this thesis proposes novel methods and uses disparate sources of data on vegetation, climate, soil, hydrology and protected areas to assess Africa’s vegetation productivity dynamics in relation to climate variability and change in the early to late 21st Century. Over 2000-2014, after accounting for contributions from human activities, subequatorial Africa was the most affected by climate-driven Net Primary Productivity (NPP) decline. Although climate generally contributed substantially to NPP improvement in areas quite north of the Equator, there was a moderate contribution from human activities. Relative to potential NPP (NPPP) estimates in 2000-2014, NPPP in the humid tropical forest and woodlands will likely be degraded in the late 21st Century because of elevated warming (RCP8.5 scenario), even under a wetter climate regime. In West Africa, this warming will likely reduce environmental suitability for growing rainfed maize in the humid savannas, currently the most suitable biome for growing this crop in the region. Although vegetation phenology across Africa is strongly associated with the seasonal dynamics of water availability, anomalies in vegetation greenness dynamics over 2003 to 2015 were less associated with anomalies in soil moisture, rainfall and terrestrial water storage (TWS), suggesting other factors may be driving these anomalies. However, among the three hydrological variables, soil moisture was more associated with vegetation greenness dynamics across much of Africa. Overall, this thesis has contributed to enhancing the understanding of the current and potential future impacts of climate variability and change on crop and vegetation productivity across Africa in the 21st Century.