A conceptual framework to describe the ecology of fragmented landscapes and implications for conservation and management

Abstract

The study of the ecology of fragmented landscapes has been dominated by two assumptions: the unique unidirectional path from larger to smaller fragments and the negligible role of fragment species on fragment properties. An accurate conceptualization of fragmented landscapes requires consideration of the age and origin of the fragments, i.e., direct fragmentation or reverse fragmentation (generation or increase of vegetated fragments by colonization), and the habitat modifications of fragment species (autogenic processes). Colonization and autogenic processes alter the fragments' composition and function. Fragment metrics affect colonization. Autogenic processes are antagonized by disturbances and modulated by abiotic inputs. Fragment alterations by autogenic processes may explain the continuous species substitution detected in some fragments or the species persistence in others. Reverse fragmentation, a natural process in commonly disturbed landscapes, challenges the avoidance-of-habitat disturbance as the ultimate strategy for biodiversity conservation and stresses the importance of pioneer species that promote succession as resilience elements in fragmented landscapes. Among-fragment diversity, generated by local disturbances, can be essential for the resilience of fragmented landscapes, suggesting that conservation and habitat utilization can be complementary processes. Traditional agroforestry systems that depend on disturbance, fragmentation, colonization, and autogenic processes may provide important insights into fragmentation ecology.