Climate Modulation of Crop Yield over the South African Highlands

Abstract This study examines climate conditions that modulate crop yield using a satellite vegetation color index in the highlands of South Africa 27°–30°S, 24°–29°E. A monthly time series is formulated (1982–2022) which exhibits large seasonality (brown winters, green summers). Correlations with detrended national maize yield exceed 0.70 in austral summer. The January–March vegetation index exhibits significant negative correlation with east Pacific and west Indian sea surface temperatures at lead times from 0 to 6 months. Persistent 3–5-yr cycles are associated with tilting of the ocean thermocline and El Niño–Southern Oscillation (ENSO), a link that has strengthened with time. Green minus brown composites exhibit a cyclonic circulation near Windhoek and a midlatitude anticyclone. Together these induce easterly winds (3 m s −1 ) that supply moisture from the Mozambique Channel. The composites show a southward shift of upwelling in the Benguela Current and a slowing and warming of the Agulhas Current. Long-term simulations by the CMIP6 ensemble predict more rain in the east and warm temperatures (+0.04°C yr −1 ) in the west. Yet, outcomes suggest that adaptation to climate change is underway and that South Africa’s crop yields may continue to rise (+0.1 t ha −1 yr −1 ) and ensure regional food security.