Abstract
There is an emerging consensus that protected areas are key in reducing adverse land-cover change, but their efficacy remains difficult to quantify. Many previous assessments of protected area effectiveness have compared changes between sets of protected and unprotected sites that differ systematically in other potentially confounding respects (e.g. altitude, accessibility), have considered only forest loss or changes at single sites, or have analysed changes derived from land-cover data of low spatial resolution. We assessed the effectiveness of protection in reducing land-cover change in Important Bird Areas (IBAs) across Africa using a dedicated visual interpretation of higher resolution satellite imagery. We compared rates of change in natural land-cover over a c. 20-year period from around 1990 at a large number of points across 45 protected IBAs to those from 48 unprotected IBAs. A matching algorithm was used to select sample points to control for potentially confounding differences between protected and unprotected IBAs. The rate of loss of natural land-cover at sample points within protected IBAs was just 42% of that at matched points in unprotected IBAs. Conversion was especially marked in forests, but protection reduced rates of forest loss by a similar relative amount. Rates of conversion increased from the centre to the edges of both protected and unprotected IBAs, but rates of loss in 20-km buffer zones surrounding protected IBAs and unprotected IBAs were similar, with no evidence of displacement of conversion from within protected areas to their immediate surrounds (leakage).
Highlights
Protected areas (PAs) form a central pillar in efforts to combat biodiversity loss and absorb a high proportion of global conservation investment [1,2]
We identified a set of sample points with similar characteristics from comparable protected and unprotected Important Bird Areas (IBAs)
The parameter estimates from the null model indicated that the annual rate of loss of natural land-cover across all points was 0.34%60.004 per year The models indicated that the annual rate of forest loss alone was over twice that of all natural land-cover (0.75%60.009)
Summary
Protected areas (PAs) form a central pillar in efforts to combat biodiversity loss and absorb a high proportion of global conservation investment [1,2]. 13% [3] to 17% by 2020, targeting expansion to areas of recognised biodiversity importance, [4], which should improve the currently poor capture by PAs of the ranges of globally threatened species [5]. A recent estimate suggests that protecting the world’s most important sites for biodiversity and meeting the target of 17% coverage might cost in the region of $76 billion annually if the target is to be met by 2020, requiring a substantial increase in current levels of spending [6]. If investment in site protection is to be enhanced, the effectiveness of PAs in reducing deleterious land-cover change needs to be quantified [7]. Several recent studies suggest that PAs are effective at reducing rates of land-cover change within their boundaries [8,9,10,11,12], but have considered only deforestation. The effectiveness of PAs at preventing conversion of all habitats in sites of high importance remains poorly quantified
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