NEW PAPER ALERT

Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography

The Plant Conservation Unit is pleased to announce the publication of an exciting new paper by Joseph White, Sam Jack, Timm Hoffman, James Puttick and others in the open-access journal, BMC Ecology. The article is entitled, "Collapse of an iconic conifer: long-term changes in the demography of Widdringtonia cedarbergensis using repeat photography". The abstract is provided below but the full paper may be downloaded here. Please also see the video abstract here. 

"Conifer populations appear disproportionately threatened by global change. Most examples are, however, drawn from the northern hemisphere and long-term rates of population decline are not well documented as historical data are often lacking. We use a large and long-term (1931–2013) repeat photography dataset together with environmental data and fire records to account for the decline of the critically endangered Widdringtonia cedarbergensis. Eighty-seven historical and repeat photo-pairs were analysed to establish 20th century changes in W. cedarbergensis demography. A generalized linear mixed-effects model was fitted to determine the relative importance of environmental factors and fire-return interval on mortality for the species."

Below is an example of a photo-pair. a Historical photograph taken by Ken Howes-Howell in 1941 and b repeat photograph taken by Timm Hoffman in 2007 at Vogelgesang, Skerpioenspoort. Thirteen living Widdringtonia cedarbergensis (green dots) and five skeletons (orange dots) were recorded in the historical photograph. Only four individuals had survived until 2007, with nine having died (red dots) and no new recruits