Managers of small reserves with modified ecosystems usually try to preserve particular features such as sand dunes in an effort to protect associated species. But fighting change may have the opposite effect and can actually cause rare species to die out, according to new research in the February issue of Biological Conservation.
“For sites to sustain their maximum diversity, it is essential that managers recognize that appropriate types of disturbance must be permitted to occur,” says author Brian Wood of University College London. “Without disturbance, the very conditions which are essential to the persistence of each plant species would not remain.”
To determine factors that affect the persistence of plant species, Wood analyzed nearly 90 years of botanical records from Blakeney Point, England, one of the few well-studied, near-natural reserves in western Europe. Managed for its internationally important breeding colonies of terns, the roughly 200-acre coastal reserve has seven natural plant communities (including saltmarsh, pebble beach, and sand dunes) and more than a third of its 206 plant species are rare. Wood focused on rare plants because managers often use their persistence as a measure of conservation success.
The Blakeney Point ecosystem is highly dynamic; for instance, over time sand dunes become fixed dunes and finally decaying dunes. During this natural progression, species richness declines by more than half, but the persistence of rare plants increases about 1.5-fold. This means that fighting change could have the unwanted side effect of hastening the demise of some rare plants.
Wood notes that both large- and small-scale disturbances are vital to maintaining overall diversity and so should be preserved by managers. “Large disturbances are important in that they clear areas that can be colonized by…plant species,” he says. “Small disturbances, which are often caused by wild animals…can provide locations for other species to inhabit.”
Wood, B. 2001. Maintaining vegetation diversity on reserves: the relationship between persistence and species richness. Biological Conservation 97:199-205.