Journal Article

Indexing the health of the environment for breeding seabirds in the Benguela ecosystem

L.G. Underhill and R.J.M. Crawford

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 3, pages 360-365
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2005.01.005
Indexing the health of the environment for breeding seabirds in the Benguela ecosystem

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Time-series of the sizes of breeding populations of 10 species of seabird were used to develop indices of the health of the Western Cape seabird community of South Africa. For each species, a target range was defined running from some minimum value to infinity or to some maximum value for species that may cause harm to other species or be a nuisance to humans. If populations were within the target range, their individual health index was set at 1, whereas outside the range, this index decreased linearly with population size. These individual indices were integrated into one for the total community, also running from 0 to 1 and therefore allowing representation as a percentage of the overall management target (=1). Three indices were developed, weighting each species equally and using different weighting methods to account for the IUCN conservation status of the species. All indices increased between the 1950s and 1970s and then decreased again, the lowest values being observed in the late 1990s.

Keywords: Benguela Current; index of health; seabirds; South Africa; target population level

Journal Article.  3637 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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