  Environmental fluctuations can create population-depleted areas and even
extinct areas for the population. This effect is more severe in the presence of
the Allee effect (decreasing growth rate at low population densities).
Dispersal inside the habitat provides a rescue effect on population-depleted
areas, enhancing the population resilience to environmental fluctuations.
Habitat reduction decreases the effectiveness of the dispersal rescue
mechanism. We report here how the population resilience to environmental
fluctuations decreases when the dispersal length or the habitat size are
reduced. The resilience reduction is characterized by a decrease of the
extinction threshold for environmental fluctuations. The extinction threshold
is shown to scale with the ratio between the dispersal length and the scale of
environmental synchrony, i.e., it is the dispersal connection between
non-environmentally-correlated regions that provides resilience to
environmental fluctuations. Habitat reduction also decreases the resilience to
environmental fluctuations, when the habitat size is similar to or smaller than
the characteristic dispersal distances. The power laws of these scaling
behaviors are characterized here. Alternative scaling functions with spatial
scales of population synchrony are found to fit the simulations worse. These
results support the dispersal length as the critical scale for extinction
induced by habitat reduction.
