Numerous studies have shown the benefits of corridors for maintaining population connectivity and promoting regional biodiversity. However, for some complex ecological process, such as seed dispersal by birds, corridors could be less effective than other connecting elements, such as stepping stones. Although seed dispersing birds may benefit from the presence of corridors, an increased corridor length or sinuous shape may induce them to spend more time in or along corridors, causing them to drop seeds before they reach suitable habitat.
In their recent paper in Landscape Ecology, Pérez-Hernández et al. show that while corridors are overall an effective management tool, they may not be the best option to maintain connectivity for all species, especially those whose dispersal depends on frugivore birds.
The authors base their work on the lingue (Persea lingue), a declining tree species endemic to southern Argentina and Chile and whose seeds are mostly dispersed by the austral thrush (Turdus falcklandii). Austral thrushes are not greatly impacted by forest loss and fragmentation, although in the presence of corridors, such as hedgerows and strips of riparian vegetation, they are more likely to follow corridor edges. This is ultimately to the detriment of lingues, since by following the corridors thrushes are more likely to drop seeds within corridors or on the pasture matrix, where lingues are unable to grow.
In this case, the increase of structural connectivity throughout the landscape leads to a decrease of functional connectivity for lingues, and they are less likely to be dispersed into favorable habitat as forest patches are more structurally connected by corridors. The authors stress that the use of corridors is still a useful and important management strategy for maintaining connectivity throughout the landscape; however, their usefulness may be species-specific, and not a guaranteed method for maintaining dispersal pathways for all species. Decisions for maintaining biodiversity should consider not only retaining corridor networks, but also other connecting elements such as stepping stones (which in this case would be more effective for lingue conservation), as well as making the open matrix more permeable.
Pérez-Hernández , C. G., P. M. Vergara, S. Saura, and J. Hernández. 2015. Do corridors promote connectivity for bird-dispersed trees? The case of Persea lingue in Chilean fragmented landscapes. Landscape Ecology 30: 77-90.