Biosecurity in New Zealand guards against threats to agriculture and biodiversity with strict border control measures being taken to prevent unwanted organisms from entering the country. New Zealand is an island nation that is geographically isolated from any significant landmass. For this reason the species that are present evolved in the absence of organisms from elsewhere and display a high degree of endemism. Notable is the lack of land based mammals, except for two species of bat. Indigenous species are at risk from population decline or extinction if any invasive species are introduced.