Ecoregion Prioritization Suggests an Armoury Not a Silver Bullet for Conservation Planning

Abstract:  In the face of accelerating species extinctions, map-based prioritization systems are increasingly useful to decide where to pursue conservation action most effectively. However, a number of seemingly inconsistent schemes have emerged, mostly focussing on endemism. Here we use global vertebrate distributions in terrestrial ecoregions to evaluate how continuous and categorical ranking schemes target and accumulate endangered taxa within the IUCN Red List, Alliance for Zero Extinction (AZE), and EDGE of Existence programme. We employed total, endemic and threatened species richness and an estimator for richness-adjusted endemism as metrics in continuous prioritization, and WWF’s Global200 and Conservation International’s (CI) Hotspots in categorical prioritization. Our results demonstrate that all metrics target endangerment more efficiently than by chance, but each selects unique sets of top-ranking ecoregions, which overlap only partially, and include different sets of threatened species. Using the top 100 ecoregions as defined by continuous prioritization metrics, we develop an inclusive map for global vertebrate conservation that incorporates important areas for endemism, richness, and threat. Finally, we assess human footprint and protection levels within these areas to reveal that endemism sites are more impacted but have more protection, in contrast to high richness and threat ones. Given such contrasts, major efforts to protect global biodiversity must involve complementary conservation approaches in areas of unique species as well as those with highest diversity and threat.

Introduction to the article

Biodiversity is vital for all humans. Despite a multitude of international agreements, local and global activism, academic debate and vast sums dedicated to conservation, the future of earth’s natural capital remains uncertain. Financial resources are highly limited and human pressure on land accelerating. Thus, ensuring the efficient allocation of resources for area selection, and thus maximum conservation impact, remains essential. Selection of “priority areas” for worldwide biodiversity conservation is a vital, but to a large extent unresolved exercise. Such areas aim to represent patterns and/or processes of biodiversity to be protected from threats to their persistence. The selection of such areas is driven by the interpretation of underpinning biological data on species, habitats and biodiversity, and by threat assessments which may include socio-economic projections such as cost analysis, economics, likelihood of managing negative human interference and projections of anthropogenic induced threat. There has been a trend to seek a single set of priority areas for conservation, but divergent approaches and metrics have appeared that have resulted in an array of different projections. Most global prioritization focuses on concentrations of individual taxa or groups of species, predominantly centred on endemism. All major institutional approaches to global biodiversity conservation prioritization operate on such an “irreplaceability/vulnerability” framework and aim for the protection of rare and endangered species rather than overall species diversity as the leading paradigm. This may be because endemics have restricted distributions, often smaller populations, and thus greater vulnerability to extinction, whereas species richness is mainly driven by widespread and non-endangered organisms. Therefore, global conservation priorities based on richness alone have not been implemented and are even regarded as of little practical use for conservation.

The metrics used to define biodiversity hotpots for conservation action remain highly controversial. The greatest challenges for priority-setting are the non-congruence of important areas defined by different indicator (surrogate) taxa and lack of correspondence of hotspots of species richness, endemism, and extinction threat. Hotspots for sites of outstanding biodiversity in danger of accelerated destruction seldom coincide across taxa. Similarly, high-resolution grid-based methods show a comparable distribution of species richness across vertebrate classes, but non-congruence for rare and threatened species and for surrogate taxa. For terrestrial ecoregions, global patterns of richness and of endemism are highly correlated amongst four terrestrial vertebrate classes, whilst the correlation between richness and endemism is low. Nevertheless, aggregate regions selected for high levels of endemism select more species than expected by chance alone, indicating that global distribution patterns of endemism can be used for the conservation of all terrestrial vertebrates. The marked differences in cross-taxon congruence of endemic species emerging from the analysis of fine-scale grids and ecoregions might be scale-dependent, but there is no a priori rationale for choice of optimal scale. Ecoregions are increasingly used as units for conservation, e.g. WWF’s Global200 Ecoregions, because of their focus on natural units of distinct communities and species assemblages. However, their full utility for priority setting remains unevaluated, especially the capture of threatened species by prioritization schemes other than endemism. Here, we close this gap by investigating how prioritizing areas by species richness, endemism and threat target and accumulate different numbers of threatened taxa.

Read the full article here.

Citation: Funk SM, Fa JE (2010) Ecoregion Prioritization Suggests an Armoury Not a Silver Bullet for Conservation Planning. PLoS ONE 5(1): e8923. doi:10.1371/journal.pone.0008923

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