Drivers and Ecological Impacts of Invasive Plant Species on Elephant Forage in Mwea National Reserve Kenya

Abstract

Studies of the ecological impacts of invasive plant species on food availability for endangered species remain limited in invasion ecology. In this study, we used purposeful sampling and established ecological equations to assess the impacts of invasive plants on elephant food resources in Mwea National Reserve, an enclosed conservation area. A total of 85 randomly distributed plots (5 m × 5 m) were established across purposively selected invaded habitat types and used to quantify the drivers and ecological impacts of invasive plant species. We hypothesized that increases in the distribution, cover, and density of invasive plant species would reduce the abundance and availability of elephant forage plants in invaded compared to non-invaded sites. We documented a total of 11 invasive species, with Parthenium hysterophorus, Senna didymobotrya, Xanthium strumarium, and Senna longiracemosa exerting the strongest negative effects on native plant cover, an indication of their competitive dominance. In contrast, Megathyrsus maximus showed a positive association with native cover, suggesting that, unlike the other invasive taxa, it may coexist with native vegetation and enhance forage availability. Riverine and ephemeral stream habitats had the highest invasive species densities (43.61 and 43.42 plants/m², respectively), while fence-line habitats had the lowest (0.96 plants/m²). Invasive species range and mean cover had a significant effect on invasiveness, including impacts on key elephant forage species (F(2,8) = 82.12, p < 0.01, R² = 0.94). The most severe ecological impacts were observed in dry season foraging areas, particularly riparian and ephemeral stream-line habitats, where species diversity declined, leading to limited foraging opportunities for elephants. We recommend management actions through manual removal of high abundant and high impactful plant invasive species. Control efforts should prioritize species based on per capita effect and ecological impact ratings, with emphasis on riverine, stream-line, and roadside habitats.

Suggested citation

Josephat Wambua, Yussuf Wato, Catherine Lukhoba, Nathaniel Gichuki (2025). Drivers and Ecological Impacts of Invasive Plant Species on Elephant Forage in Mwea National Reserve KenyaGlobal Journal of Enviromental Science & Sustainability, 2(2). https://doi.org/10.69798/92249762

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