Forest-Grassland Mosaics  and Alternative Stable States

Forest-grassland  mosaic  ecosystems  can  exhibit  alternative stables states, whereby under the same environmental conditions, the ecosystem could equally well reside either in one state or another, depending on the initial conditions. We develop a mathematical model that couples a simplified forest-grassland mosaic model to a dynamic model of opinions about conservation priorities in a population, based on perceptions of ecosystem rarity.  Weak human influence increases  the  region  of  parameter  space  where  alternative stable states are possible. However, strong human influence precludes  bistability,  such  that  forest  and  grassland either co-exist at a  single, stable equilibrium, or their relative abundance oscillates. Moreover, a perturbation can shift the system from a stable state to an oscillatory state. We conclude that human-environment interactions can qualitatively alter the composition of forest-grassland mosaic ecosystems. The human role in such systems should be viewed as dynamic, responsive element rather than as a fixed, unchanging entity.