Transformation and fragmentation of habitats are the major drivers of biodiversity losses. The two processes are almost always simultaneous and their combined effect on population trends is yet unaccounted for. We quantified the degree to which habitat transformation and fragmentation have driven decreases of red-listed animal populations worldwide. Shifts in population trends may serve as early warnings for future extinctions and may help guide the efforts by nature conservation institutions.
We determined the remaining intact forest area still available for species subsistence and their degree of fragmentation, using maps of species extent of occurrence and of the world's intact forests (see Figure 1). We then determined the odds of species population decreases with increasing transformation and fragmentation of forest habitats. Additional explanatory variables included taxonomic class, feeding habits, additional suitable habitats to species, and quality of land surrounding intact forest patches (Figure 2).
Figure 1. Intact forest patch i (IFPi) as the remaining suitable forest habitat for species s. OAs, LSIFPi and ndi represent, respectively, the original area available for s (prior to land transformation), the land cover type surrounding IFP and the nearest distance of patch i to another suitable patch for s.
In the absence of additional suitable habitats (that are either natural or human-made), amphibians are most likely to undergo population decreases. Moreover, the statistical model performed better with habitat transformation alone than with combined transformation and fragmentation effects.
Ligia B. Azevedo of Radboud University, Nijmegen, Netherlands, is a citizen of Brazil. She was funded by IIASA's Brazilian National Member Organization and worked in the Ecosystems Services and Management (ESM) Program during the YSSP.
Please note these Proceedings have received limited or no review from supervisors and IIASA program directors, and the views and results expressed therein do not necessarily represent IIASA, its National Member Organizations, or other organizations supporting the work.
Last edited: 19 August 2015
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