Multiscale drivers of sugarcane expansion and impacts on water resources in Southern Africa

Abstract

The reality of sugarcane expansion and intensification across Southern Africa is one that requires greater scrutiny than is currently the case, particularly considering the impacts of sugarcane production on water resources in this region. This study made use of a frequency analysis approach to ascertain the multiscale proximate and ultimate drivers of sugarcane production as reported in 87 case studies across the uMngeni, Ubombo and Kilombero Catchments in South Africa, Swaziland and Tanzania, respectively. Further, using a relationship between observed sugarcane yields and future low, medium and high production scenarios, the objective of this study was to develop water use estimates for rainfed and irrigated sugarcane over six production cycles, viz. 2013/14–2019/20. Results indicated that ultimate drivers such as foreign direct investment and increased local and international demand for sugar play the most dominant role in the expansion of sugarcane production regionally and within each catchment. Thus, water use may be anticipated to increase in response to increased production intensity, particularly in the medium and high growth scenarios, though this may be mitigated by increased water use efficiency and the development and adoption of improved cane crop varieties. More detailed water use modelling studies are required to account for critical aspects related to crop water use such as changes to temperature, evapotranspiration and CO2 concentration because of climate change and increased climate variability. This will provide useful policy advice for regional agricultural development initiatives.