How invasive species eradication benefits biodiversity?


A global study was published in February 2016 in the journal Proceedings of the National Academy of Sciences.

A team of thirty scientists, including Nick Holmes, Director of Science at Island Conservation, found that :

596 populations of 236 native species on 181 islands benefited from 251 eradications.

These results are promising for the future of conservation and biodiversity.


The study indicates that invasive species eradication offers major potential conservation gains at relatively low financial investment.

Eradication is a successful conservation strategy because it does more than alleviate the threats posed by invasive species–it eliminates them entirely.

Once an island is free of invasive species, its native wildlife can thrive.

Gallicolombe érythroptère ©Thomas Ghestemme

Polynesian Ground-dove ©Thomas Ghestemme

Read more: Invasive mammal eradication on islands results in substantial conservation gains


Global conservation actions to prevent or slow extinctions and protect biodiversity are costly.

However, few conservation actions have been evaluated for their efficacy globally, hampering the prioritization of conservation actions.

Islands are key areas for biodiversity conservation because they are home to more than 15% of terrestrial species and more than one-third of critically endangered species; nearly two-thirds of recent extinctions were of island species.

This research quantifies the benefits to native island fauna of removing invasive mammals from islands.

Our results highlight the importance of this conservation measure for protecting the world’s most threatened species.


More than US$21 billion is spent annually on biodiversity conservation. Despite their importance for preventing or slowing extinctions and preserving biodiversity, conservation interventions are rarely assessed systematically for their global impact.

Islands house a disproportionately higher amount of biodiversity compared with mainlands, much of which is highly threatened with extinction. Indeed, island species make up nearly two-thirds of recent extinctions. Islands therefore are critical targets of conservation.

We used an extensive literature and database review paired with expert interviews to estimate the global benefits of an increasingly used conservation action to stem biodiversity loss: eradication of invasive mammals on islands.

We found 236 native terrestrial insular faunal species (596 populations) that benefitted through positive demographic and/or distributional responses from 251 eradications of invasive mammals on 181 islands.

Seven native species (eight populations) were negatively impacted by invasive mammal eradication.

Four threatened species had their International Union for the Conservation of Nature (IUCN) Red List extinction-risk categories reduced as a direct result of invasive mammal eradication, and no species moved to a higher extinction-risk category.

We predict that 107 highly threatened birds, mammals, and reptiles on the IUCN Red List—6% of all these highly threatened species—likely have benefitted from invasive mammal eradications on islands.

Because monitoring of eradication outcomes is sporadic and limited, the impacts of global eradications are likely greater than we report here.

Adult Tahiti Monarch©Fred_JACQ

These results highlight the importance of invasive mammal eradication on islands for protecting the world’s most imperiled fauna.