Résumé
Even when environments deteriorate gradually, ecosystems may shift
abruptly from one state to another. Such catastrophic shifts are difficult
to predict and sometimes to reverse (so-called hysteresis). While well
studied in simplified contexts, we lack a general understanding of how
catastrophic shifts spread in realistically spatially structured
landscapes. For different types of landscape structures, including typical
terrestrial modular and riverine dendritic networks, we here investigate
landscape-scale stability in metapopulations whose patches can locally
exhibit catastrophic shifts. We find that such metapopulations usually
exhibit large-scale catastrophic shifts and hysteresis and that the
properties of these shifts depend strongly on the metapopulation spatial
structure and on the population dispersal rate: an intermediate dispersal
rate, a low average degree or a riverine spatial structure can largely
reduce hysteresis size. Our study suggests that large-scale restoration is
easier with spatially clustered restoration efforts and in populations
characterized by an intermediate dispersal rate.