Persistence, accuracy and timeliness: finding, mapping and managing non-native plant species on the island of South Georgia (South Atlantic)

Résumé

The South Georgia ecosystem-based habitat restoration project is a major project that began with the eradication of invasive rats (Rattus norvegicus) and reindeer (Rangifer tarandus), 2011–2017. As part of this restoration programme a non-native plant management strategy was developed and implemented. With only 8% of the whole South Georgia landmass suitable for vascular plants (ca. 283 km²) due to permanent ice and bare rock, there have been 25 indigenous vascular plants and 41 non-native plants recorded from earlier surveys. Following removal of grazing pressure from introduced mammals, surveys were conducted to quantify the current status and distribution of non-native plant populations and enable a non-native plant control strategy to be developed for the island. Due to the vast scale of the island, multiple seasons were required to carry out rapid surveys of key indicators such as species, area of plant coverage in square metres and age class (mature or juvenile). Survey and control data were entered into a spatial database to enable analysis, allow data-informed management decisions and be used for long-term control-based monitoring of outcomes. During this series of surveys, 44 naturalised, non-native plant species were identi?ed and mapped. Of these, 34 species are now being managed at zero density with 56,851 m2 at 184 sites controlled to date; four are managed at speci?c sites with 22,443 m2 controlled to date, three require con?rmation of species and the remaining three species are widely established and receive limited control. Spatially quantifying the distribution and control of non-native plants has enabled the development and implementation of an e?ective management strategy which contributes to the restoration of South Georgia’s native biodiversity.