CHAPTER 31
CONSERVATION OF BIOLOGICAL DIVERSITY IN BOTANICAL GARDENS

PETER S.ASHTON

Director, Arnold Arboretum, Harvard University, Cambridge, Massachusetts

Conservation is already, and very appropriately, recognized as being a major activity for botanical gardens in both their research and educational programs. In this field, arboreta and botanical gardens have a particular and important potential, which I discuss in this chapter.

In nature, plants frequently exist in small populations. Examples include many rare endemics, such as those of mountain peaks and many in the Mediterranean dry sclerophyll scrublands, especially in the Cape Province of South Africa and in Southwest Australia, and those of certain rain forests. Over the relatively short time we realistically have had to work as conservation managers, extremely small stands have been found to persist in nature. Higher plants, being sedentary, are often highly site-specific. This facilitates the development of logical plans for demarcating minimal areas for in situ conservation based on ecological knowledge and principles of island biogeography. On the whole, the most favorable sites are a few environmentally heterogeneous reserves of sufficient size to minimize edge effects (e.g., changes in species composition at the periphery caused by in- and out-migrations from adjacent unprotected lands). Ideally, these would be loosely connected by small stepping stones or corridors to allow for the exchange of genes (Diamond, 1975). Identification and immediate protection of sites of high conservation value must be our highest priority in the absence of even the grossest information upon which to base plans, including basic inventory as well as distributional and ecological data on many of the richest biota. This underlines the vital necessity of increasing inventory and ecological information as a prerequisite to developing any logical plan for conservation. In practice, of course, the luxury of regional planning often does not exist. The conservationist only succeeds in



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