Older Forests Have Irreplaceable Value for Conservation, Study Finds

There’s been a lot of wildlife losses over the past several decades and a tenth of the wilderness has disappeared since the 1990s. This research on forests and birds is a reminder that that there’s still much that needs to be done to get human activities on a better track.

Old, complex tropical forests support a wider diversity of birds than second-growth forests and have irreplaceable value for conservation, according to an Oregon State University-led exhaustive analysis of bird diversity in the mountains of southern Costa Rica.

During their surveys, researchers found similar numbers of bird species in secondary stands compared to stands comprised entirely or in part of old-growth forest. However, the bird community in secondary forest was clearly shifted towards non-forest species, and only old-growth forest stands tended to include rare birds and to benefit biodiversity across the entire landscape. Scientists reported their results this week in the Journal of Applied Ecology.

The findings are important because in some cases, conservation programs have focused on the potential benefits of secondary forests. Although secondary forests do have value for conservation, the study suggests that primary forests are necessary as sources of biodiversity and as a refuge for species that can colonize other sites that are being restored. Thus, these results suggest that a strategy focussing only on second-growth forests may not benefit conservation-relevant species. Indeed, such stands tend to support only a few common species that can survive in highly disturbed areas.


Effective conservation efforts should include maintenance of large old-growth forest tracts, the scientists wrote, and insure that human activities in the forest do not drive away species that depend on such areas. The results also suggest that restoring forests is likely to be most effective for forest birds if such efforts are performed in the vicinity of primary forest. This is likely because primary forest will provide a source for forest birds that may colonize the restored forest. Relying on secondary forests alone may create “potentially misleading expectations,” researchers wrote, that landscapes significantly modified by people can still accomplish conservation goals.

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