From the text (p.78) ... 'There is another, more important reason why assisted migration must be a management option of last resort. My logic is simple and based not on the biology of the target species, in this case Florida torreya, but on conservation concerns of the recipient ecosystem. Humanity has a long record of tinkering with natural ecosystems. Largely these have been successful from the perspective of the human endeavor -- think agriculture. This tinkering, however, creates a series of ancillary non-target biological winners and losers. It has been argued that the majority of species introduced have had little effect on ecosystem structure, and most introductions do not cause undue ecological damage (Mack et al. 2000). Nevertheless, those few cases where introduced populations rapidly expand and threaten to endanger other species or damage ecosystems and ecosystem functions cost the U.S. billions of dollars each year (U.S. Congress 1993, Pimentel et al. 2000). As a consequence, I believe that conservationists should be very reticent about introducing species to novel environments as a conservation measure. Societal recognition of an appropriate reticence toward species introductions has been slow, but is emerging (Mack et al. 2000). If we are to now advocate species introductions on behalf of conservation, conservationists must have clear guidance as to when this action is warranted and when it is not. It is not an action to be taken lightly.'