Tuesday, April 15, 2008

Megapark for elephants

Here's an interesting paper from Biological Conservation last year that uses several of the ideas we talked about today, particularly metapopulations and sources and sinks. But in this case, when the species of concern is elephants, we have an interesting situation - too many elephants in an area can be too much of a good thing. They trample crops, come into conflict with people and can damage vegetation in conservation areas. In this case the authors suggest that the establishment of sinks may be a good thing that prevents populations in the sources from becoming too numerous.

We support the development of one or more networks of conservation areas that will allow the southern African sub-region’s elephants to be driven by metapopulation dynamics. Inevitably, our model must provide for both source and sink populations. This can be achieved by allowing dispersal from sources, including many existing conservation areas, to sinks. In doing so, our approach links source populations within a megapark context. We advocate that the landscape matrices between conservation areas act primarily as sinks. By the very nature of sinks, here elephant mortality rates must be greater than birth rates, while populations are maintained by immigration from sources. Such immigration should limit numbers in source populations. In restoring this type of metapopulation structure, elephant numbers could be prevented from increasing locally to levels that are deemed undesirable in sources.

Megaparks for metapopulations: Addressing the causes of locally high elephant numbers in southern Africa by Rudi J. van Aarde, Tim P. Jackson
Biological conservation 134, 3, Pages 289-297

No comments: