The 1974 Noxious Weed Act provides authority to control 75 species of weeds which come into the US on ships, planes, in water and dry ballast, and in agricultural commodities. However, there is a major problem with the listing system for noxious weeds it takes too long to get dangerous invaders listed for exclusion. Witchweed is a root parasite on corn and sorghum from Africa. It is also spread by raccoon, deer, and infested sod. If such invasions continue, the Earth will become simpler and poorer biologically instead of six bioregions, there will be one.
Biological pollution is the single most underestimated threat to sustainability.
We generally wait until things get out of hand before we do anything about them. Prevention is always better and cheaper than a cure. We need to use caution in the movement to free trade. If we become a true global village, the final chapter of biological invasion may come to pass. People who want to bring in nonnative species for profit should have to prove that the species has never been a problem as a weed or invader elsewhere.