Modelling potential habitat suitability of three invasive alien plant species under projected climate scenarios and land-use/land-cover change in the Lake Zone of Tanzania

Résumé

Invasive alien plant species pose significant ecological and socio-economic risks across East Africa, yet invasion risk assessments in Tanzania have largely relied on single-species and climate-only projections. Such approaches may overestimate invasion potential by neglecting land-use constraints and inter-model uncertainty. This study evaluates current and future habitat suitability of three invasive species, Chromolaena odorata and Lantana camara (terrestrial), and Eichhornia crassipes (aquatic) in the Mara–Simiyu region of northern Tanzania. Habitat suitability was modelled using MaxEnt and spatial block cross-validation. Projections were generated under three CMIP6 climate models (ACCESS-CM2, MIROC6, MRI-ESM2-0) and three emission pathways (SSP1–2.6, SSP3–7.0, SSP5–8.5). The suitable area was quantified using the 10th percentile training presence (P10) threshold, and ensemble predictions were derived by averaging across climate models. Climate-only projections indicate that terrestrial species retain moderate suitability under low-emission scenarios but experience increasing fragmentation and contraction of highly suitable areas under higher-emission pathways. Niche overlap between L. camara and C. odorata was moderate to high across scenarios (Schoener’s D = 0.45–0.81), suggesting substantial climatic similarity and potential spatial convergence under future warming. In contrast, E. crassipes maintained broad climatic suitability across scenarios. When land-use projections were incorporated, suitable habitat estimates were substantially reduced and exhibited greater spatial uncertainty. For C. odorata , suitable habitat covered approximately 55–65% of the region under SSP1–2.6, but this uncertainty increased under high-emission scenarios (coefficient of variation ≈ 65–75% by 2090). L. camara showed even stronger contractions, with uncertainty exceeding 85–90% under SSP5–8.5. These findings suggest that climate-only models may overestimate potential niche space by ignoring land-use constraints. Therefore, integrating multiple environmental drivers provides a more realistic assessment of invasion risk and supports climate-adaptive management strategies.

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