Here today, here tomorrow: beached timber in Gabon, a persistent threat to nesting sea turtles

Pikesley, Stephen K.;Agamboue, Pierre Didier;Bonguno, Eric Augowet;Boussamba, François;Cardiec, Floriane;Fay, J. Michael ;Formia, Angela;Godley, Brendan J.;Laurance, William F.;Mabert, Brice Didier Koumba;Mills, Cheryl;Mounguengui, Gil Avery Mounguengui;Moussounda, Carine;Ngouessono, Solange;Parnell, Richard J.;Sounguet, Guy-Philippe;Verhage, Bas;White, Lee;Witt, Matthew J.

William Laurance

Abstract

The African country of Gabon has seen decadal increases in commercial logging. An unforeseen consequence of this has been that many coastal areas, including several National Parks and Reserves, have suffered severe pollution from beached timber. This has the potential to adversely affect nesting sea turtles, particularly the leatherback turtle (Dermochelys coriacea) for which Gabon constitutes the world's largest rookery. In this study, we analyse aerial survey data (2003, 2007 and 2011) to determine the temporal persistence and spatial extent of beached timber, and by integrating spatial data on nesting, ascertain regions where beached timber poses the greatest threat to nesting leatherback turtles. There was no marked difference in the number of beached logs recorded across the study area during the period, with 15,160, 13,528 and 17,262 logs recorded in the three years, respectively. There was, however, a significant difference in abundance of beached logs among geographical areas. Analysis highlighted two coastal areas where nesting leatherback turtles were likely to be at greatest risk from beached timber. At one such site, Kingere, within Pongara National Park, where both logs and turtle densities are high, monitoring in 2006/2007 and 2007/2008 suggested that between 1.6% and 4.4% of leatherback turtles could be entrapped at this site. Given the dynamic nature of Gabon's coastal environment, and the potential limitations of aerial surveys, densities of beached timber could be greater than this analysis reveals. We also propose, that despite recent export restrictions of whole logs, their environmental persistence potentially represents a long-term problem.

Journal

Biological Conservation

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162

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1873-2917

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Elsevier

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DOI

10.1016/j.biocon.2012.11.002