As tropical landscapes continue to become more fragmented, questions abound over whether biodiversity and ecosystem services can be maintained in the long term. Isolated patches are more likely to leave species without way to carry out ecosystem services, unless those patches retain some sort of connectivity between them.
A new study by Kormann et al. asks whether narrow wooded corridors, such as living fencerows and tree lines, can be effective in conserving ecosystem services, specifically pollination by hummingbirds. They focused on the tropical forest landscape of Southern Costa Rica, where pastures for agriculture have replaced much of the native habitat. Using artificial flowers to attract individuals between both connected and unconnected patches, they looked at how hummingbirds moved through the landscape and where pollination services occurred.
They found four striking results:
- Corridors strongly enhanced the movement of habitat specialist hummingbirds, but were less important for habitat generalist species.
- Corridors can substantially mitigate the impediment provided by pastures for pollen flow in hummingbird-pollinated flowers, although this positive effect dampens at increasing distances.
- Corridors were key drivers in whether habitat specialist hummingbirds occupied a patch. One common specialist, the Green Hermit Phaetornis guy, was virtually absent from unconnected patches. This absence was mirrored by a breakdown in pollination of a common understory herb, Heliconia tortuosa, despite the presence of habitat generalist species.
- Corridors were successful in supporting both species movement and pollination services, despite being narrow (often only one or two trees wide).
These results strongly support the benefits of corridors, even when small and in highly fragmented landscapes. Although the size of corridors in these studies may be effective mostly for small, highly mobile species such as hummingbirds, the strong results show that simple measures such as living fence rows and narrow tree lines can be highly effective in maintaining critical ecosystem services.
Sometimes it only takes a small link to provide a huge conservation benefit.
Resources
Kormann, U., C. Scherber, T. Tschamtke, N Klein, M. Larbig, J. J. Valente, A. S. Hadley, and M. G. Betts. 2016. Corridors restore animal-mediated pollination in fragmented tropical forest landscapes. Proc. R. Soc. B 283: 20152347.
