Isolation
Drake 15 (Nadia Drake, 6-23-2015, "Will Humans Survive the Sixth Great Extinction?," National Geographic News, https://www.nationalgeographic.com/news/2015/06/150623-sixth-extinction-kolbert-animals-conservation-science-world/) ank
Island populations are very vulnerable to extinctions for a couple of reasons. They tend to have been isolated. One of the things we’re doing is removing the barriers that used to keep island species isolated. New Zealand had no terrestrial mammals. Species that had evolved in the absence of such predators were incredibly vulnerable. A staggering number of bird species have already been lost on New Zealand, and a lot of those that remain are in deep trouble. So, places that have been isolated for a long time. Those are very vulnerable. Species that have a very restricted range, that exist only in one spot in the world, those tend to be extremely vulnerable. They have nowhere to go and if their habitat is destroyed, say, then they’re gone.