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Dramatic decline in orang-utan numbers in the Leuser Ecosystem, Northern Sumatra

Published online by Cambridge University Press:  24 April 2009

Carel P. van Schaik,
Kathryn A. Monk and
J. M. Yarrow Robertson
Kathryn A. Monk
Affiliation:
Research, Monitoring, and Information Division, Leuser Management Unit, JI. Dr Mansyur 68, Medan 20154, Indonesia
J. M. Yarrow Robertson
Affiliation:
Conservation Management Division, Leuser Management Unit, JI. Dr Mansyur 68, Medan 20154, Indonesia
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Abstract

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The Leuser Ecosystem, northern Sumatra, Indonesia, contains the world's largest orang-utan Pongo pygmaeus population. We examine the consequences of the recent wave of forest conversion, and legal and illegal logging, on orang-utan numbers in the Leuser Ecosystem. We review density variation inside the Leuser Ecosystem and its causes, and the consequences of selective logging, exhaustive logging and clear-felling for habitat conversion on orang-utan densities. The analysis of the orang-utan's decline is based on information on forest loss, logging intensity, and the delineation of logging concessions and legal changes in land use status. The results indicate a very rapid decline, by c. 45 per cent, from c.. 12,000 in early 1993, over a 6- to 7-year period. During 1998 and 1999, losses occurred at a rate of about 1000 orang-utans per year. At this rate, further losses in the near future are expected to put the survival of Leuser's orang-utans in serious doubt.

Keywords

Conversionfragmentationillegal loggingorang-utanplantationsselective loggingSumatra

Information

Type
Research Article
Information
Oryx , Volume 35 , Issue 1 , January 2001, pp. 14 - 25
Copyright
Copyright © Fauna and Flora International 2001

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