Ken Thompson

“A survey of oceanic (i.e. remote) islands found that, as far back as records exist, they have been accumulating alien plants. In 1860 the average oceanic island had less than 1 introduced plant for every 10 natives. By 1940 the ratio was 1 alien for every 2 natives, and today the ratio is about 1:1. Despite all these new arrivals there have been very few extinctions among the original inhabitants, so the number of plant species on such islands has approximately doubled. Thus, although left to themselves remote islands tend to have rather few species (compared to similar continental areas at the same latitude), so many species have been introduced to Hawaii that it now has as many plants as a similar area of Mexico. Moreover, the evidence suggests that remote islands are by no means ‘full’ of plants, and that there is room for even more alien plants to establish, and thus for total plant diversity to increase: at the current rate the average oceanic island will have 3 aliens for every 2 natives by 2060. Do we have any idea how many different plant species might eventually be able to coexist on an island like Hawaii? No, we don’t. Or, to express that conclusion in a more general form, in a report from US ecologists Dov Sax and Steve Gaines: ‘we have a relatively poor understanding of the processes that ultimately limit how many species can inhabit any given place or area”
― Ken Thompson, Where Do Camels Belong?: Why Invasive Species Aren't All Bad