Preventing invasive species from getting to an island and establishing a breeding population is the most effective measure. Prevention involves identifying the pathways which an invasive species may use to get to an island, assessing the risk of these and applying procedures to minimise each risk. This aspect should be done at all times, particularly before any travel (including the project teams) to the island. All existing and potential invasive species should be considered, i.e. invasive species to be eradicated as part of the project and any that are not currently on the island but could pose a threat. Prevention is also sometimes referred to as quarantine. The trick is to put in as many obstacles as possible along different parts of the pathway to reduce the ease of movement of the invasive species.

Rats are agile climbers and use mooring lines to board boats
Rats are agile climbers and use mooring lines to board boats
(Photo: Global Invasives Species Database)


Surveillance is monitoring to detect whether an incursion has occurred. An incursion is when an invasive species has evaded the prevention measures and arrived on the island. This is a long-term activity, with on-going or regular monitoring in place on the island.

Incursion Response

A project management decision-making plan will be in place that assists with the planning of how to confirm that an incursion has occurred, what further information is required and what is the best way to handle the incursion.

If the surveillance suggests that an incursion has occurred, the project team need to respond to the threat. A range of information will be required to decide how to react, for example:

  • What is the invasive species?
  • What size is the incursion? (e.g. a single animal/plant, small group of animals/plants, large number of animals/plants)
  • What is the breeding status etc of the animals/plants? (e.g. lactating female; immature juvenile)
  • How long has the species been on the island? (i.e. recent incursion or old incursion that has gone undetected)

Community involvement in Biosecurity

As most pathways involve people travelling to the island much of the prevention work will be undertaken, not by the project team but by the wider public and especially local communities and island visitors. Get the input of local communities and island users to help work out biosecurity measures that will be effective in the local situation. Identify what they value on invasive free islands (e.g. larger harvest from crops as rodents are not eating them) so they have an interest in keeping the island invasive-free. Visitors need to be taught which invasive species threaten the island and what they need to do to prevent re-invasion. This will require the project team to conduct a public awareness exercise and consult widely with stakeholders to inform the public of the role they can play and to motivate them to take biosecurity seriously.