Savannah–forest dynamics: encroachment speed, model inference and spatial simulations
Year: 2026
Type: article
Abstract: Forest encroachment over savannahs has been recurrently reported in the tropics over the last few decades, especially in northern tropical Africa. However, process-based, spatially explicit modelling of the phenomenon is still trailing broad-scale empirical observations. In this paper, we use remotely sensed diachronic data from Central Cameroon to calibrate a simple reaction-diffusion model, embodying dynamical interactions between grass and woody biomasses in the savannah biome. Landsat satellite image series over the Mpem and Djim National Park (MDNP) (Cameroon) witnessed a dramatic extension of forest over the last five decades, and our estimates of forest front speeds based on randomly sampled transects indeed yield higher values (5-7 m yr-1) than in the existing literature (0.5-2 m yr-1). We use model simulations to provide the first estimates of woody biomass dispersal coefficients. Since the study region did not provide examples of savannah progression, estimates of grass dispersal proved inconsistent and we reverted to literature-based historical data to reach rough estimates. We demonstrate that broad-scale remote sensing data allows for calibrating simple reaction-diffusion models of vegetation dynamics in the savannah biome. Such calibrated models become a general baseline of expected changes and a valuable tool to understand how spatial environmental factors may locally modulate the overall dynamics.
Institutions: Swedish University of Agricultural Sciences, Centre National de la Recherche Scientifique, Centre de Coopération Internationale en Recherche Agronomique pour le Développement, Université de Yaoundé I, Université de Montpellier, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement, UMR Botanique et Modélisation de l’Architecture des Plantes et des végétations, Institut de Recherche pour le Développement, École Nationale Supérieure Polytechnique de Yaoundé, University of California, Los Angeles, Institut de Recherche Agricole pour le Développement
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
SDGs: Life on land, Climate action
Open Access status: hybrid
OpenAlex ID: W7164941602