The global contribution of invasive vertebrate eradication as a key island restoration tool

Abstract

Islands are global hotspots for biodiversity and extinction, representing ~ 5% of Earth's land area alongside 40% of globally threatened vertebrates and 61% of global extinctions since the 1500s. Invasive species are the primary driver of native biodiversity loss on islands, though eradication of invasive species from islands has been effective at halting or reversing these trends. A global compendium of this conservation tool is essential for scaling best-practices and enabling innovations to maximize biodiversity outcomes. Here, we synthesize over 100 years of invasive vertebrate eradications from islands, comprising 1550 eradication attempts on 998 islands, with an 88% success rate. We show a significant growth in eradication activity since the 1980s, primarily driven by rodent eradications. The annual number of eradications on islands peaked in the mid-2000s, but the annual area treated continues to rise dramatically. This trend reflects increases in removal efficacy and project complexity, generating increased conservation gains. Our synthesis demonstrates the collective contribution of national interventions towards global biodiversity outcomes. Further investment in invasive vertebrate eradications from islands will expand biodiversity conservation while strengthening biodiversity resilience to climate change and creating co-benefits for human societies.

Figure 1

The island locations of all invasive vertebrate eradication events, 1872–2019. Each purple dot represents an eradication event on an island, with darker dots indicating higher numbers of eradication events.

Figure 2

Trends in invasive vertebrate eradications over time, 1900–2019. Cumulative numbers and annual numbers are presented in the left and right columns, respectively. Panels represent the number of eradication events (a, b), treated island area (c, d), number of countries implementing eradications (e, f), number of invasive species targeted (g, h). Panels a and c display the three modes of nested data: all events, completed events, and successful events; the remaining panels display all eradication events.

Figure 3

Eradication timeline analysis, 1900–2019. Significant periods of change over time are shown for the eradication metrics displayed as curves in Fig. 2 (annual number of eradication events (2b), treated island area (2d), countries implementing eradications (2f), invasive taxa targeted for eradication (2h)) and Fig. 4 (eradication success rate). Significant periods are indicated when lasting five or more years: positive gradient (i.e., increasing slope, wide green bar), positive curvature (i.e., acceleration; narrow dark bar), and negative curvature (i.e., deceleration; narrow white bar). There were no periods of significant negative gradient (i.e., decreasing slope) for any of the analyzed metrics.

Figure 4

Eradication method trends by area, 1900–2019. Cumulative island areas targeted annually with the application of each major eradication method (a) and the human habitation status on those islands (b).

Figure 5

Annual success rates of completed eradication events, 1900–2019. Each point represents a success rate calculated for all events in a year with ≥ 5 eradication events (calculated as successful events/[successful + failed events]). Gray shading represents 95% confidence intervals.