Using a large-scale biodiversity monitoring dataset to test the effectiveness of protected areas at conserving North-American breeding birds

Victor Cazalis,Ana S.L Rodrigues,Soumaya Belghali

doi:10.24072/pcjournal.5

Abstract

Protected areas currently cover about 15% of the global land area, and constitute one of the main tools in biodiversity conservation. Quantifying their effectiveness at protecting species from local decline or extinction involves comparing protected with counterfactual unprotected sites representing what would have happened to protected sites had they not been protected. Most studies are based on pairwise comparisons, using neighbour sites to protected areas as counterfactuals, but this choice is often subjective and may be prone to biases. An alternative is to use large-scale biodiversity monitoring datasets, whereby the effect of protected areas is analysed statistically by controlling for landscape differences between protected and unprotected sites, allowing a more targeted and clearly defined measure of the protected areas effect. Here we use the North American Breeding Bird Survey dataset as a case study to investigate the effectiveness of protected areas at conserving bird assemblages. We analysed the effect of protected areas on species richness, on assemblage-level abundance, and on the abundance of individual species by modelling how these metrics relate to the proportion of each site that is protected, while controlling for local habitat, altitude, productivity and for spatial autocorrelation. At the assemblage level, we found almost no relationship between protection and species richness or overall abundance. At the species level, we found that forest species are present in significantly higher abundances within protected forest sites, compared with unprotected forests, with the opposite effect for species that favour open habitats. Hence, even though protected forest assemblages are not richer than those of unprotected forests, they are more typical of this habitat. We also found some evidence that species that avoid human activities tend to be favoured by protection, but found no such effect for regionally declining species. Our results highlight the complexity of assessing protected areas effecti veness, and the necessity of clearly defining the metrics of effectiveness and the controls used in such assessments.

Highlights

The increasing human footprint on natural ecosystems is leading to major declines in species’ populations (McRae et al, 2016) and has already resulted in thousands of extinctions (IUCN, 2018), to such an extent that Ceballos et al (2017) characterised current times as a period of “biodiversity annihilation”
Neither species richness nor summed abundance were significantly affected by the proportion of protected areas (PAs) in models that did not control for vegetation structure
This is not surprising, as several large-scale studies found that assemblage metrics – species richness – are relatively resilient to disturbance through species substitution (Dornelas et al, 2014; Supp and Ernest, 2014)

Summary

Introduction

The increasing human footprint on natural ecosystems is leading to major declines in species’ populations (McRae et al, 2016) and has already resulted in thousands of extinctions (IUCN, 2018), to such an extent that Ceballos et al (2017) characterised current times as a period of “biodiversity annihilation”. Modern PAs have their origins in the 19th century and currently represent the most important conservation tool, with about 15% of the global land area already protected to some extent, and coverage planned to reach 17% by 2020 (UNEP-WCMC IUCN, 2016). There is a substantial literature on PA effectiveness: as of the 1st October 2018, 260 publications in the Web of Science included in their title “protected AND area* AND effective*”. Within this literature there are disparate approaches to the concept of “effectiveness”

Methods

Results

Conclusion