Abstract
Protected area downgrading, downsizing, and degazettement (PADDD) has been documented worldwide, but its impacts on biodiversity are poorly understood. To fill this knowledge gap, we reviewed historical documents to identify legal changes that altered the boundaries of Yosemite National Park. We identified two downsizes and five additions between 1905 and 1937 that reduced the size of Yosemite National Park by 30%. To examine the effects of these downsizing events on habitat fragmentation by roads, we compared protected, never-protected, and downsized lands at three spatial scales using four habitat fragmentation metrics: road density, fragment (land surrounded by roads) area-to-perimeter ratio, fragment area, and fragment density. In general, lands that were removed from protection, e.g., downsized, were more highly fragmented than protected lands and indistinguishable from never-protected lands. Lands where downsizes were reversed were less fragmented than lands where downsizes were not reversed. These results suggest that protected area downsizing may exacerbate habitat fragmentation, a key contributor to biodiversity loss globally. Furthermore, the case study in Yosemite National Park demonstrates that iconic protected areas in developed countries are not immune to downsizing. These findings underscore the need to account for PADDD and governance histories in ecological research, monitoring, and evaluation. As we move toward more evidence-based conservation policy, a rigorous understanding of PADDD is essential to ensure that protected areas fulfill their promise as a strategy for conserving global biodiversity.
Highlights
Habitat fragmentation is a well-documented threat to global biodiversity (Fischer and Lindenmayer 2007, Krauss et al 2010, Haddad et al 2015) driven by natural and anthropogenic factors
Protected area downgrading, downsizing, and degazettement (PADDD) has been documented worldwide, but its impacts on biodiversity are poorly understood. To fill this knowledge gap, we reviewed historical documents to identify legal changes that altered the boundaries of Yosemite National Park
As we move toward more evidence-based conservation policy, a rigorous understanding of PADDD is essential to ensure that protected areas fulfill their promise as a strategy for conserving global biodiversity
Summary
Habitat fragmentation is a well-documented threat to global biodiversity (Fischer and Lindenmayer 2007, Krauss et al 2010, Haddad et al 2015) driven by natural and anthropogenic factors. Habitat fragmentation may compound the threat of climate change; for example, roads may prevent the migration of species attempting to adapt to a warming climate (Brodie et al 2012). Roads that fragment habitat have additional consequences for biodiversity. Documented effects of roads on wildlife include increased mortality from road construction and vehicle collisions, behavior modifications, alteration of the physical and chemical environments, and the spread of invasive species (Forman and Alexander 1998, Trombulak and Frissell 2000). Effects of roads on wildlife are largely negative, especially for amphibians and reptiles (Fahrig and Rytwinski 2009)
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