Earlier this month I blogged about how beautiful wild orchids are under threat from indiscriminate plant collecting to satisfy the itch of orchid-fanciers to own the rarest and most delicate species in their gardens.
However, plant collecting does not always have a sad ending. The Victorian plant collectors who harvested rhododendrons and orchids in obscene quantity from the Himalayan uplands also ventured to other countries. In Japan, they came after the country ended its isolation from the West in 1854, and collected many species which found their way into British gardens and parks. Now, these same species are endangered in their native habitat, but relatively common in cultivation.
Preserving an endangered species outside its native environment is called ex-situ conservation. It's not ideal: they're largely removed from their natural interactions, the context is lost, and reintroducing them could be problematic, especially for animals with complex behaviors. Furthermore, only a few individuals can typically be preserved, so much of the genetic diversity is inevitably lost. However, with careful curation, like with the captive breeding programmes carried out in zoos, it is possible to minimize loss of genetic diversity in the existing captive gene pools and avoid inbreeding.
The article I linked to ends on a pessimistic note: all countries are having to deal with extinction of their native flora and fauna, to a greater or lesser extent. Ex-situ conservation can only help to a small extent, though anything is better than nothing at all.
In our anthropogenic age (what some people are calling the Anthropocene), with species being shuffled all over the globe and having their ways of life permanently changed, maybe it won't make sense to talk about native or non-native any more, except as a sort of historical documentation of what we have lost.
I'm not saying that tracts of the remaining "wild" nature are not worth preserving: the rain forests, taiga, and coral reefs are valuable for being as close to "native" as we can get. What I'm thinking of are the extreme cases of domesticated landscapes–much of old Europe, East Asia, and Mesopotamia–where any hope of reviving a pre-human species palette is impossible. Barring any great human cataclysm, the rest of the world will inevitably become more and more like these places over time.