Four decades of Eucalyptus water use and productivity in South Africa (1985–2025): progress, innovations and emerging frontiers

Globally, Eucalyptus plantations increasingly play a major role in the socio-economy through the supply of industrial roundwood. However, water use (WU) of Eucalyptus remains a controversial issue and its impact on water resources is well documented. This review synthesises four decades (1985–2025) of WU and productivity research conducted on commercial Eucalyptus species in South Africa, while drawing on insights from international studies. A systematic review approach was adopted in this study. The review begins by exploring early Eucalyptus WU research on Eucalyptus grandis W.Hill ex Maiden (in the mid-1980s), highlighting key findings and how this shaped subsequent WU research in South Africa. During the early 2000s, the WU and water use efficiency (WUE) research focus shifted from E. grandis to Eucalyptus dunnii Maiden and clonal hybrids. Key results from these studies are presented, including potential water sources by Eucalyptus. After 2010, advances in technology, including artificial intelligence (AI) and satellite imagery, transformed Eucalyptus WU research from single-plot measurement to WU estimation at regional and global scales. This development significantly expanded both the scope and precision of WU and productivity research worldwide. However, these technologies are still in developmental stages in South African commercial Eucalyptus plantations. Concurrently, plantation water productivity (PWPWOOD) has been proposed as a more appropriate indicator of Eucalyptus productivity compared with traditional WUE. Despite significant progress in WU research, critical gaps remain. These include: the need for long-term Eucalyptus WU research; the expansion of the WU research network to represent various management practices, such as planting density and silvicultural regimes; a wider range of climates, soils, species, and stand densities; the broader adoption of PWPWOOD as an alternative indicator of productivity; and the development of AI and remote sensing-based models for estimating Eucalyptus WU patterns under South African conditions, supported by in situ measurements for ground truthing. This synthesis consolidates four decades of research progress and presents a forward-looking framework aimed at strengthening WU research in South Africa.