Wild About Wilderness: Natural Land Halves Extinction Risk of its Inhabitants

Wilderness areas - areas of unmodified natural land - have been found to halve the extinction risk of terrestrial species found in them.

Wilderness areas like Kahurangi National Park in New Zealand are vital habitats for endangered species like kea and takahe (Credit: Poppy Simon)

A lot of attention has been given to the degradation of wilderness areas and the resulting extinction of species that lived in them, but less so to how wilderness supports the continuing presence of biodiversity.

A team of researchers from Australia and the US has now tried to address this, using vascular plants (basically most of what we tend to think of as plants, excluding things like mosses and ferns) and invertebrates. Plants and invertebrates were chosen to represent terrestrial biodiversity because of their diversity and distribution; they represent the largest proportion of diversity according to number of species (invertebrates) and total weight a.k.a. biomass (plants).

By mapping spatial variation in species composition, the researchers were able to estimate the proportion of species across a given landscape that were expected to persist long-term, and therefore also the proportion estimated to go extinct. They discovered that the chance of extinction for a given species in non-wilderness areas was more than twice as high as for that in wilderness areas.

The models that wilderness areas have a buffering effect against extinction risk that is particularly pronounced where there are higher areas of wilderness left, like the Palearctic biogeographical realm (all of Eurasia north of the Himalayas, and North Africa). In the Indomalayan realm (South, Southeast and southern East Asia), on the other hand, species had the highest overall risk of extinction, and the lowest wilderness coverage.

As you might expect, the persistence of species in wilderness areas was highly dependent on the undisturbed habitats found there, but many species outside wilderness areas also depended on these habitats too. Once again, this was particularly the case in where there are high areas of wilderness, for example in the Amazon basin. In the Afrotropical realm, however, which has less wilderness, there were some areas like the Namib desert where unmodified land provided important refuge for species present in both wilderness- and non-wilderness areas, and others (the Kalahari, for example) where the wilderness areas remaining were did not have much impact on the persistence of biodiversity.

To conclude their study, the researchers identified wilderness areas where habitat loss would have the biggest negative impact on biodiversity. All of these spots are not currently well-protected, and the authors call for targeted protection as well as efforts to restore former wilderness areas that have been degraded.

https://doi.org/10.1038/s41586-019-1567-7

Di Marco, M., Ferrier, S., Harwood, T.D. et al. Wilderness areas halve the extinction risk of terrestrial biodiversity. Nature 573, 582–585 (2019).