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Modelling spatiotemporal dynamics of wattle plantations in northwestern Ethiopia using harmonised PlanetScope and RapidEye imagery
   

Modelling spatiotemporal dynamics of wattle plantations in northwestern Ethiopia using harmonised PlanetScope and RapidEye imagery

Celuxolo Michal Dlamini, Trylee Nyasha Matongera, Simon Lawson, Madaline Healey, Agena Tanga, Kumela Regasa, Weldesenbet Kassie, Brett Phillip Hurley Ilaria Germishuizen
Trees, Forests and People, Vol.25, pp.1-14
2026
: https://doi.org/10.1016/j.tfp.2026.101293

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Published Version Open Access
Random forest Remote sensing Uromycladium acaciae Wattle plantations
Plantation forests within agroforestry systems play a critical role in supporting rural livelihoods across sub-Saharan Africa, yet their sustainability is increasingly threatened by land-use change, demographic pressure, and emerging biotic threats. In Awi Zone of Ethiopia, wattle (Acacia spp.) plantations are widely cultivated by smallholders, providing timber, fuelwood, charcoal, and income, while also contributing to soil amelioration and reducing pressure on natural forests. However, their invasive tendencies can also drive biodiversity loss and disrupt ecosystem services beyond intended planting sites. Balancing these benefits against ecological risks remains a global challenge. This study assesses the spatiotemporal dynamics of wattle plantations and associated Land Use Land Cover (LULC) changes in the Awi Zone from 2013 to 2025, with particular attention given to recent declines potentially linked to the emergence of wattle rust disease (Uromycladium acaciae). PlanetScope (3–5 m) and RapidEye (5 m) satellite images were harmonised and classified on Google Earth Engine (GEE) using a Random Forest classifier to generate LULC maps for five epochs (2013, 2016, 2019, 2022, and 2025). Classification performance was consistently high [Overall Accuracy (OA) 0.80–0.93; Kappa 0.70–0.91] for all periods. Change detection analysis indicated rapid expansion of wattle plantations between 2013 and 2016 (+181%) followed by a sustained and consistent decline with most pronounced gross loss of 181 km2 (24.8%) between 2019 and 2022, largely driven by conversion to Other vegetation and alternative LULC classes. The trend continued until 2025, with a further 27.7% reduction in wattle plantation area to 527 km2. Although rotational agroforestry practices partly explain cyclical changes, the timing and magnitude of recent declines may indicate that wattle rust reduced plantation viability and encouraged transitions to alternative land uses. This study highlights the value of remote sensing in monitoring disease risks, land-use pressures, and livelihood sustainability.
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