These issues are unlikely to be solved with simple -- or complex! -- solutions. Here in California, the recent cases of Sudden Oak Death Syndrome and the light brown apple moth demonstrate a wide range of post facto futilities. The first case is likely to be catastrophic, the effects of the latter remain to be seen. Certainly treating the entire US as a single ecosystem is nonsensical. And I find the "clean stock" requirement advocated by the Nature Conservancy to be particularly menacing, recalling not only the troubles of the Dutch and Oregon Bulb Farms mentioned by Iain, but our own scorched earth agro-industrial landscapes: http://sfgate.com/cgi-bin/article.cgi/… Food for thought, whatever your ideological convictions about government: when I went to look up that last article, the top story on the SF Chronicle website is about how the US Immigration and Customs department is locking up and deporting US citizens. Max Withers Oakland CA