POPULATION SPATIAL STRUCTURE, HUMAN-CAUSED LANDSCAPE CHANGES AND SPECIES SURVIVAL

Population survival depends on the spatial structure of the population , which is defined as the set of local populations that make up the po pulation and the probability of exchange of individuals among them. Th erefore, population spatial structure depends on the interaction betwe en the landscape spatial pattern and the dispersal characteristics of the organisms. Human activities have profound effects on population sp atial structure. Habitat loss decreases the number of local population s and therefore decreases overall population size. This results in a d ecrease in the number of dispersers available for recolonization and r escue of local populations, which further reduces overall population s ize. Eventually local extinctions can accumulate to regional extinctio ns. Habitat fragmentation per se exacerbates this problem by increasin g the probability of local extinction. However, the effects of habitat loss far outweigh the effects of fragmentation per se. Species intera ctions are a critical component of ecosystem function, and alterations of population structure by human activity have significant effects on them. Mutualisms may be disrupted, coexistence may be either increase d or decreased, predator-prey interactions may be destabilized, and ne w predator-prey interactions may be introduced. Realistic predictions of the effects of changes in landscape pattern on population survival and population interactions depend on an accurate understanding of the ir effects on population spatial structure.