We cannot escape risk, because we cannot stop change. So what was a safe bet before becomes a risky bet, because the variables keep shifting.

Keeping species in their current habitats could lead to their extinction if they're unable to adjust to the local effects of climate change. Expanding contiguous wild habitat may make it easier for animals and plants to incrementally migrate in response to changing conditions, so let's do all we can on that front. But there will be man-made and natural barriers to migration and in those cases we'll have to directly intervene and move vulnerable species to new habitats.

These new inhabitants will become "invasive species". So be it. We will have to manage the risk.

Reference:

Ove Hoegh-Guldberg, Lesley Hughes, Sue McIntyre, David Lindenmayer, Camille Parmesan, Hugh Possingham & Chris Thomas. Moving with the times: assisted colonization and rapid climate change. Science, July 18, 2008