Management Action-Restoration

New Zealand’s offshore and outlying islands have long been a focus of conservation biology as sites of local endemism and as last refuges for many species. During the c. 730 years since New Zealand has been settled by people, mammalian predators have invaded many islands and caused local and global extinctions. New Zealand has led international efforts in island restoration. By the late 1980s, translocations of threatened birds to predator-free islands were well under way to safeguard against extinction.

Invasive alien mammals are the major driver of biodiversity loss and ecosystem degradation on islands. Over the past three decades, invasive mammal eradication from islands has become one of society's most powerful tools for preventing extinction of insular endemics and restoring insular ecosystems. As practitioners tackle larger islands for restoration, three factors will heavily influence success and outcomes: the degree of local support, the ability to mitigate for non-target impacts, and the ability to eradicate non-native species more cost-effectively.

Ramsey Island, 259 ha, is ca. 1 km off the Pembrokeshire coast, south-west Wales. The eradication of brown rats (Rattus norvegicus) was successfully completed in the winter 1999/2000 using a ground-based bait station operation. The pre-eradication survey using tape playback estimated the Manx shearwater (Puffinus puffinus) population to be 849 pairs. These surveys were repeated in 2007, 2012 and 2016. Each survey showed the Manx shearwater population had increased, reaching 4,796 pairs in 2016 with birds spreading from previously known breeding locations.

Ecological restoration is a common tool to mitigate the loss of species and habitats, ultimately aiming to restore ecosystem functioning. Large-scale experimental evidence is lacking, however, on whether standard management techniques, e.g. the removal of invasive alien plants, indeed restore ecosystem functions at the community level. One key ecosystem function is animal mediated pollination.

As the ?rst step towards the ecological restoration of its islands, Mexico has completed 60 eradications of invasive mammals thanks to a strong partnership between Grupo de Ecología y Conservación de Islas, A.C. (GECI), the federal government, local ?shing communities, academia, and private donors. The removal of invasive mammals has led to the dramatic recovery of the islands’ ecosystems. On Guadalupe Island, after completing the goat eradication in 2007, the native vegetation started to recover.

The Seychelles was one of the ?rst tropical island nations to implement island restoration resulting in biodiversity gain. In the 2000s a series of rat eradication attempts was undertaken in the inner Seychelles islands which had mixed results. Three private islands with tourist resorts successfully eradicated rats: Frégate (2000), Denis Island (2003) and North Island (2005). Frégate Island was successful with the ?rst eradication attempt whereas North and Denis Islands were initially unsuccessful, and both required second eradication operations.

In recent decades Seychelles has accumulated extensive experience in the management of invasive species and other island restoration practices. Non-government organisations (NGOs), governmental, parastatal and private stakeholders have conducted successful programmes to control and eradicate invasive animals and plants, particularly on small islands of high biodiversity value. Biosecurity protocols have been implemented to prevent (re)infestations.