Abstract
Protected Areas (PAs) are core components of conservation strategies, but the networks they form are rarely assessed for their effectiveness over time. We tested different aspects of effectiveness of the British PA network in achieving long-term biodiversity outcomes, including species representativeness of initial location choices and network resilience (in terms of species persistence). Using 10 × 10 km cells, ‘landscapes’, with contrasting cover of protected areas managed specifically for biodiversity conservation, we evaluated these aspects of effectiveness by analysing species distribution changes of over 2800 species of animals and plants from 1974 to 2014. Landscapes that contained PAs in 1974 had higher species representativeness than landscapes without PAs, but landscapes with low PA coverage (<median) were more representative than those with high PA coverage (>median). Many species distributions have declined since 1974, and the distributional trends of declining and priority species were similar (on average) in landscapes containing PAs and in the wider countryside, implying PA-containing landscapes were not resilient to landscape-scale pressures. Nonetheless, PAs did have a small positive impact over time on landscape-scale representation trends of declining species, and priority species. Regardless of PA coverage, topographically heterogeneous landscapes were more likely to retain priority species between 1974 and 2014, and less likely to be colonised by expanding species. Despite landscapes with low PA coverage disproportionately contributing to overall PA network representativeness, they are less resilient than landscapes with high PA coverage, which jeopardises their value in the long-term and will require landscape-scale habitat conservation and restoration to address.
Highlights
Species declines continue globally (Pimm et al, 2014; Ceballos et al, 2015; Secretariat of the Convention on Biological Diversity, 2020), and conservation efforts to prevent them have been largely unsuccessful (Hoffmann et al, 2010; Johnson et al, 2017)
We found comparable results for every species category (Table A4), with the exception that the landscapes with highest Protected areas (PAs) coverage (80% quantile ‘high PA’ areas) did not have higher priority species representation than ‘PA absent’ landscapes (Table A10)
If Systematic Conservation Planning (SCP) had been used at the baseline date, optimised through spatial prioritisation using Zonation, the initial network representativeness would have improved
Summary
Species declines continue globally (Pimm et al, 2014; Ceballos et al, 2015; Secretariat of the Convention on Biological Diversity, 2020), and conservation efforts to prevent them have been largely unsuccessful (Hoffmann et al, 2010; Johnson et al, 2017). PA extent is increasing, and higher coverage targets are likely as part of the post-2020 global biodiversity framework (Bhola et al, 2021; CBD, 2020), assessing the effectiveness of PA networks (the set of all PAs within an area) is essential in understanding the degree to which they contribute to the long-term conservation of nature This requires a multi-faceted evaluation of all component PAs of the network: both of initial establishment locations, usually in terms of representativeness of species or habitats; and the extent to which long-term biodiversity outcomes are achieved through appropriate management and PA network design (Rodrigues and Cazalis, 2020). Evaluating representativeness (representation of the full variety of biodiversity within the PA network (Kukkala and Moilanen, 2013)) is important, but it is only one facet of long-term nature conservation, and understanding biodiversity outcomes through time is just as important in evaluating network effectiveness (Nicholson et al, 2006; Rodrigues and Cazalis, 2020)
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