Rewilding the world's large carnivores

Abstract

Earth's terrestrial large carnivores form a highly endangered group of species with unique conservation challenges. The majority of these species have experienced major geographical range contractions, which puts many of them at high risk of extinction or of becoming ecologically ineffective. As a result of these range contractions and the associated loss of intact predator guilds, the ecological effects of these species are now far less widespread and common, with inevitable consequences for ecosystem function. Rewilding-which includes reintroducing species into portions of their former ranges-is an important carnivore conservation tool and means for restoring top-down ecological regulation. We conducted a global analysis of potential reintroduction areas. We first considered protected areas where one or more large carnivore species have been extirpated, identifying a total of 130 protected areas that may be most suitable for carnivore reintroduction. These protected areas include sites in every major world region, and are most commonly found in Mongolia (n = 13), Canada (n = 11), Thailand (n = 9), Namibia (n = 6), Indonesia (n = 6) and Australia (n = 6). We considered the sizes of protected areas, their levels of protection, the extent of human impacts within and around the protected areas, and the status of prey species in the protected areas. Finally, we used the 'last of the wild' approach to identify contiguous low human footprint regions within the former ranges of each species, identifying an additional 150 areas which could be the focus of conservation efforts to create conditions conducive to reintroductions. These low footprint regions were most commonly found in the USA (n = 14), Russia (n = 14), Canada (n = 10), China (n = 9) and Mauritania (n = 8). Together, our results show the global-scale potential for carnivore rewilding projects to both conserve these species and provide critical ecological and social benefits.

Keywords: carnivore guild; ecological effectiveness; geographical range; intact guild; predator; reintroduction.

Figure 1.

The 25 terrestrial large carnivore species in our analysis (table 1). From left to right, the species are: first row—African wild dog, American black bear, Andean black bear, Asiatic black bear, brown bear; second row—brown hyaena, cheetah, clouded leopard, dhole, dingo; third row—Ethiopian wolf, Eurasian lynx, gray wolf, jaguar, leopard; fourth row—lion, puma, red wolf, sloth bear, snow leopard; fifth row—spotted hyaena, striped hyaena, sun bear, Sunda clouded leopard, tiger. Scientific names are given in table 1 and photo credits are given in electronic supplementary material, table S1.

Figure 2.

Histograms for human footprint (a spatial measure of human impacts on the environment) across the historic ranges of each large carnivore species. The historic range (both colours together) is split into ‘Current range’ (regions where the carnivore species is still present) and ‘Lost range’ (regions where the carnivore species has been extirpated). The vertical lines indicate thresholds for ‘last of the wild’ regions within lost ranges. That is, the bottom 10% threshold (quantile) for human footprint in the lost range.

Figure 3.

Potential sites for reintroducing large carnivores. (a) The locations, areas and mean human footprints of the six largest strictly protected areas within each of the 25 large carnivores' lost ranges (i.e. where the species has been extirpated). (b) The same data for the six largest low footprint regions within the lost range of each species. Low footprint regions were determined based on contiguous areas within the ‘last of the wild’ regions of each large carnivore's lost range. ‘Last of the wild’ regions are those in the bottom 10% for human footprint within each species' lost range.

Figure 4.

The six largest protected areas inside the ‘lost’ (historic minus current) ranges of each large carnivore species (only three were identified for the red wolf). For each carnivore species, variables shown are mean human footprint across the protected area, region of the world, and whether or not the large carnivore guild becomes complete following reintroduction of the carnivore species. Only strictly protected (IUCN categories I–III) were considered for this analysis. Asia is split into southeastern Asia and the rest of Asia (denoted ‘Asia’).

Figure 5.

Corridors among the 411 protected areas that we identified as candidate sites for large carnivore reintroduction based on the 25 largest protected areas for each large carnivore species. The protected areas are shown in green. Corridors between protected areas were identified using Linkage Mapper and are coloured according to their value based on compositing normalized cost-weighted distance rasters, with higher composite corridor values corresponding to greater potential contributions to connectivity. We used the human footprint map (linearly rescaled to range from 1 to 100) as the resistance raster for calculating cost distances, with areas containing cropland masked out. A 500 km Euclidean distance threshold was used to avoid mapping corridors between protected areas that are more than 500 km apart. Note that zooming can be used to view detail in this figure.