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.

Figure 1. Accumulation of species over prioritized ecoregion ranks.

Target species are EDGE (A), AZE (B), Red List's critically endangered CR (C) and Red List's endangered EN (D) species. Lines represent accumulations of species when incrementally increasing the number of included ecoregions, which were continuously prioritized by species richness (blue), endemism (red), ∂-endemism (black), and threat (Red List categories CR+EN; green). Grey lines denote mean, 5% and 95%confidence limits when ecoregions are randomly selected (10000 simulations). Symbols represent species in ecoregions selected by the Global200 (circles) and Conservation International's Hotspots (diamonds; larger x-values for ecoregions within or overlapping Hotspots; smaller x-values for ecoregions within Hotspots).

Figure 2. Accumulation of species over prioritized ecoregion area.

Target species are EDGE (A), AZE (B), Red List's critically endangered CR (C) and Red List's endangered EN (D) species. Lines and symbols as in Figure 1.

Figure 3. World map of ecoregions ranked according to species richness, endemism, ∂-endemism and threat.

The congruence of the 100 highest ranking ecoregions of each prioritization scheme is shown (endemism only: yellow, ∂-endemism only: orange; richness only: turquoise; two, three or all metrics: light, medium or dark purple, respectively). Small islands, which are too small to be seen on the map, are highlighted by hatching.

Figure 4. Average human footprint (A) and the percentage of protected area (B) over prioritized ecoregion rank.

Lines represent values when incrementally increasing the number of included ecoregions, which were continuously prioritized by species richness (blue), endemism (red), ∂-endemism (black), and threat (Red List categories CR+EN; green). Symbols represent ecoregions selected by the Global200 (circles) and Conservation International's Hotspots (diamonds; larger x-values for ecoregions within or overlapping Hotspots; smaller x-values for ecoregions within Hotspots). Human footprint data and protected area sizes are from the WWF databases. The human footprint refers to the average footprint index, ranging from 0 to 100, and is scaled here to 100 square kilometres.