Satellite-Based Assessment of Vegetation Dynamics and their Potential Drivers in Lochinvar National Park Using Google Earth Engine

Abstract

This study examines vegetation dynamics and their potential environmental drivers in Lochinvar National Park, Zambia, over a 41-year period (1984 to 2025), using Landsat imagery processed on Google Earth Engine (GEE). The specific objectives were to: (1) quantify long-term land-cover change across six classes, namely water, grassland, woodland, floodplain, Mimosa pigra, and mine area; (2) characterise vegetation greenness trends using the Normalized Difference Vegetation Index (NDVI); and (3) examine the spatial association between these changes and hydrological alteration, invasive species spread, and human activity. The guiding research question was: how have vegetation cover and greenness in Lochinvar National Park changed since 1984, and to what extent are these changes spatially associated with hydrological, biological, and anthropogenic pressures? Using a Random Forest classifier (500 trees) applied to nine dry-season composite periods, grassland increased from 161.85 km² (39.31%) in 1984-1988 to 185.21 km² (44.99%) in 2024-2025, a net gain of 23.36 km² (+5.68 percentage points), while floodplain area declined from 114.32 km² (27.77%) to 76.89 km² (18.68%), a net loss of 37.43 km² (-9.09 percentage points). Mimosa pigra extent fell from a peak of 42.05 km² (10.22%) in 1994-1998 to 31.87 km² (7.74%) by 2024-2025. Classification accuracy reached 92% overall in the final period. Maximum NDVI fluctuated between 0.385 and 0.447 across the record, with a shallow positive linear trend of approximately +0.0004 NDVI units per year. These patterns are spatially consistent with, though not statistically proven to be caused by, altered flooding regimes downstream of the Itezhi-Tezhi and Kafue Gorge dams, sustained Mimosa pigra control efforts, and continued anthropogenic pressure. The study contributes an empirical, cloud-based monitoring framework that can inform smart, data-driven, and evidence-based land-management policy for wetland protected areas in Zambia and comparable floodplain systems in the region.