Effects of protected area downsizing on habitat fragmentation in Yosemite National Park (USA), 1864 – 2014

Abstract

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 To fill this knowledge gap, we reviewed historical documents to identify legal changes that altered the boundaries of Yosemite National Park.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.

Protected area downgrading, downsizing, and degazettement as a threat to iconic protected areas

“…The 1905 downsizing was partially offset through the addition of 293 km 2 of land to the park (Golden Kroner et al. ).…”

“…Conversely, lands that regained protection, even decades later, are less fragmented than lands that remain unprotected, demonstrating the value of long‐term land protection and the value of reversing PADDD to maintain ecosystem connectivity (Golden Kroner et al. ).…”

“…Specifically, the Yosemite case study demonstrates that restoring protections may reduce impacts on areas relative to those where PADDD remains in place (Golden Kroner et al. ), revealing a temporal element to the impacts of PADDD which is yet to be investigated in other PADDD research.…”

“…The park was downgraded in 1892 to allow construction of wagon roads and turnpikes; in 1901 for electrical lines, dams, and pipes; and in 1913 for the construction of O'Shaughnessy Dam in the Hetch Hetchy Valley (Golden Kroner et al 2016). The park was downsized in 1905 and 1906 to accommodate forestry and mining activities, removing legal protections from 1,309.30 km 2 (34% of its original 3,886 km 2 ) (Golden Kroner et al 2016). The 1905 downsizing was partially offset through the addition of 293 km 2 of land to the park (Golden Kroner et al 2016).…”

“…Proximate causes of PADDD include industrial-scale resource extraction and development, local land pressures and land claims, and, to a much lesser extent, conservation planning (Mascia et al 2014). Although the Convention on Biological Diversity (CBD) calls for protecting 17% of terrestrial area by 2020, PADDD not only hinders national progress toward Aichi Target 11 (Mascia et al 2014), but may also accelerate tropical deforestation and carbon emissions (Forrest et al 2015) and exacerbate habitat fragmentation (Golden Kroner et al 2016).…”