Data from: Dispersal increases the resilience of tropical savanna and forest distributions

Global change may induce changes in savanna and forest distributions, but
the dynamics of these changes remain unclear. Classical biome theory
suggests that climate is predictive of biome distributions, such that
shifts will be continuous and reversible. This view, however, cannot
explain the overlap in the climatic ranges of tropical biomes, which some
argue may result from fire-vegetation feedbacks, maintaining savanna and
forest as bistable states. Under this view, biome shifts are argued to be
discontinuous and irreversible. Mean-field bistable models, however, too,
are limited as they cannot reproduce the spatial aggregation of biomes.
Here, we suggest that both models ignore spatial processes, such as
dispersal, which may be important when savanna and forest abut. We examine
the contributions of dispersal to determining biome distributions using a
2D reaction-diffusion model, comparing results qualitatively to empirical
savanna and forest distributions in sub-Saharan Africa. We find that the
diffusion model resolves both the aforementioned limitations of biome
models. First, local dispersive spatial interactions, with an underlying
precipitation gradient, can reproduce the spatial aggregation of biomes
with a stable savanna-forest boundary. Second, the boundary is not only
determined by the amount of precipitation but also by the geometrical
shape of the precipitation contours. These geometrical effects arise from
continental-scale source-sink dynamics, which reproduces the mismatch
between biome and climate. Dynamically, the spatial model predicts that
dispersal may increase the resilience of tropical biome in response to
global change: the boundary continuously tracks climate, recovering
following disturbances, unless remnant biome patches are too small.