Predicting future land cover degradation through the integrated use of the Cellular-Automata-Markov chain model and the Trends.Earth model: An application in the Upper Zambezi River Basin in southern Africa

Attaining a “land degradation neutral world” by 2030, as envisaged by the United Nations (UN) 2030 agenda for sustainable development, sustainable development goal (SDG) number 15, requires accurate information for the implementation of targeted interventions. The Trends.Earth historical data set to support monitoring and reporting, and to track the impact of sustainable land management is only available up to the year 2021. However, combining the predictive ability of Cellular-Automata-Markov (CA-Markov) model(s) in Idris Selva and the Trends.Earth model could provide an insight into potential future land cover degradation. Therefore, this study assesses the status of the land cover degradation in the Upper Zambezi River Basin (UZB) in southern Africa using the CA-Markov model and the Trends.Earth model. The UZB includes the headwaters of the Zambezi River and is susceptible to land cover degradation with potential negative effects on water resources. High resolution multispectral Landsat data are used in the Land Change Modeler (LCM) and the CA-Markov chain model in Idris Selva 17.0 to assess historical changes and predict future changes in land use and land cover (LULC) for the period 1993-2033. The LULC change maps produced with the LCM and CA-Markov models in Idris Selva are used to assess the land cover degradation status for the period 1993-2033 in the UZB using the Trends.Earth model in QGIS 3.34. Results show that land cover degradation maps produced, at local level, from high spatial resolution multispectral data provides more detail of land cover degradation compared to the Trends.Earth global data set. In terms of land cover degradation, the UZB is largely stable. However, of concern are areas, including wetlands and the headwaters of the Zambezi River, which shows land cover degradation as a result of loss of forest cover to expansions in human settlements and cropland. On the contrary, some areas show improvements in forest cover due to conversion of grassland and cropland into forest cover. For the period 2023 – 2033 the forest cover in the UZB is predicted to have a net reduction of 236258 hectares at a net annual rate of -0.14%. The spatial extent of land cover degradation is projected to build-up on the historical spatial extent. Predicting land cover degradation, as demonstrated in this study, makes available information for instituting targeted interventions which may help in the monitoring and management of water resources, as well as contribute towards a land degradation neutral world.