A proposal made by a group of Australian ecologists in the current issue of Science. This is what they said regarding the bioinvasion risk:
"One of the most serious risks associated with assisted colonization is the potential for creating new pest problems at the target site. Introduced organisms can also carry diseases and parasites or can alter the genetic structure and breeding systems of local populations. However, most major pest problems have been created by continent-to-continent and continent-to-island translocations or by the transfer of organisms between distinct biogeographic regions within continents (e.g., Nile perch to Lake Victoria). Clearly, risks escalate as species are moved across biogeographical boundaries. Introduction of the cane toad, Bufo marinus, from its native range in tropical America to Australia and various tropical parts of the world has been disastrous. This is not the scale of translocation that is being proposed here; we are not recommending placing rhino herds in Arizona or polar bears in Antarctica. We are, however, advocating serious consideration of moving populations from areas where species are seriously threatened by climate change to other parts of the same broad biogeographic region (i.e., broad geographic regions that share similar groups of organisms)."