Savannah–forest dynamics: encroachment speed, model inference and spatial simulations
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.
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BibTeX
@article{zelnik2026savannahforest,
title = {{Savannah–forest dynamics: encroachment speed, model inference and spatial simulations}},
author = {Yuval R Zelnik and Ivric Valaire Yatat-Djeumen and Le Bienfaiteur Sagang and Pierre Couteron},
journal = {Journal of the Royal Society Interface},
year = {2026},
month = sep,
doi = {10.1098/rsif.2025.0502},
url = {https://hal.inrae.fr/hal-05744779v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Savannah–forest dynamics: encroachment speed, model inference and spatial simulations
AU - Yuval R Zelnik
AU - Ivric Valaire Yatat-Djeumen
AU - Le Bienfaiteur Sagang
AU - Pierre Couteron
PY - 2026
DA - 2026/09/09
JO - Journal of the Royal Society Interface
DO - 10.1098/rsif.2025.0502
UR - https://hal.inrae.fr/hal-05744779v1
AB - 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.
SN - 1742-5689
SN - 1742-5662
ER -