Abstract

Unsustainable exploitation of natural resources is increasingly affecting the highly biodiverse tropics [1Gibson L. Lee T.M. Koh L.P. Brook B.W. Gardner T.A. Barlow J. Peres C.A. Bradshaw C.J.A. Laurance W.F. Lovejoy T.E. Sodhi N.S. Primary forests are irreplaceable for sustaining tropical biodiversity.Nature. 2011; 478: 378-381Crossref PubMed Scopus (1338) Google Scholar, 2Harrison R.D. Sreekar R. Brodie J.F. Brook S. Luskin M. O’Kelly H. Rao M. Scheffers B. Velho N. Impacts of hunting on tropical forests in Southeast Asia.Conserv. Biol. 2016; 30: 972-981Crossref PubMed Scopus (143) Google Scholar]. Although rapid developments in remote sensing technology have permitted more precise estimates of land-cover change over large spatial scales [3Hansen M.C. Potapov P.V. Moore R. Hancher M. Turubanova S.A. Tyukavina A. Thau D. Stehman S.V. Goetz S.J. 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Evol. 2006; 21: 227-229Abstract Full Text Full Text PDF PubMed Scopus (170) Google Scholar]. Here we use field survey data, predictive density distribution modeling, and remote sensing to investigate the impact of resource use and land-use changes on the density distribution of Bornean orangutans (Pongo pygmaeus). Our models indicate that between 1999 and 2015, half of the orangutan population was affected by logging, deforestation, or industrialized plantations. Although land clearance caused the most dramatic rates of decline, it accounted for only a small proportion of the total loss. A much larger number of orangutans were lost in selectively logged and primary forests, where rates of decline were less precipitous, but where far more orangutans are found. This suggests that further drivers, independent of land-use change, contribute to orangutan loss. This finding is consistent with studies reporting hunting as a major cause in orangutan decline [8Meijaard E. Buchori D. Hadiprakarsa Y. Utami-Atmoko S.S. Nurcahyo A. Tjiu A. Prasetyo D. Nardiyono Christie L. Ancrenaz M. et al.Quantifying killing of orangutans and human-orangutan conflict in Kalimantan, Indonesia.PLoS ONE. 2011; 6: e27491Crossref PubMed Scopus (107) Google Scholar, 9Davis J.T. Mengersen K. Abram N.K. Ancrenaz M. Wells J.A. Meijaard E. It’s not just conflict that motivates killing of orangutans.PLoS ONE. 2013; 8: e75373Crossref PubMed Scopus (49) Google Scholar, 10Abram N.K. Meijaard E. Wells J.A. Ancrenaz M. Pellier A.-S. Runting R.K. Gaveau D. Wich S. Nardiyono Tjiu A. et al.Mapping perceptions of species’ threats and population trends to inform conservation efforts: the Bornean orangutan case study.Divers. Distrib. 2015; 21: 487-499Crossref Scopus (32) Google Scholar]. Our predictions of orangutan abundance loss across Borneo suggest that the population decreased by more than 100,000 individuals, corroborating recent estimates of decline [11Santika T. Ancrenaz M. Wilson K.A. Spehar S. 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Sci. 2012; 1249: 29-44Crossref PubMed Scopus (62) Google Scholar].Video AbstracteyJraWQiOiI4ZjUxYWNhY2IzYjhiNjNlNzFlYmIzYWFmYTU5NmZmYyIsImFsZyI6IlJTMjU2In0.eyJzdWIiOiI3NzVlYzU2MTRjYjE4ODA4MjVhMDA4YWJmYWYyNDFhNCIsImtpZCI6IjhmNTFhY2FjYjNiOGI2M2U3MWViYjNhYWZhNTk2ZmZjIiwiZXhwIjoxNjc5NDU5NDc0fQ.DEdrG_57cF2PVxBVL7RCtHsBb34aDZwKkCWA2ONCYwmMex4IeydL84VKN4SlSZtNubJ2oa5mkhGjwUWAVhcBGK88nGsWQESZt_couVkgn4BGMiIDaIZ_fw3dXRO1mh4vukubXw02PSJemxUf8I-5GmdlbrlyPoCIUfW5cMlCojOE29xvPLh9zm-Hadsbt-Eh4ICHu9lc2Q_TAf2Ox8Xb8hmHqSpKZyWUHYHVGLXoWj5ZRFaa2-KxNBaRLqfsuJWzIe_LB6VCed_XDRUUgQaOeyQTi16QSmouceYD-rs3FADDiH8WFxaDFhdH-NnYUngUuz0Oefv7UjpctrSfxBhXyg(mp4, (42.59 MB) Download video