Implementing policies to control invasive plant species.

Plant imports by the North American horticultural industry risk the accidental introduction of harmful nonnative species. An annual license fee paid by the industry would reduce this risk while raising funds for research, screening imported species, education, and the eradication of past plant invasions. However, implementing such a fee requires information on how long it takes introduced species to become established and on their spread rates and environmental damages. Implementing such a policy would be challenging in terms of the scientific data required to estimate the correct tax. There is also limited support among stakeholders for an annual fee compared with other policy options to stop invasives. The preferred policy is to screen all newly introduced plants and to ban those species with a high likelihood of becoming a potential invasive. Mandatory implementation of this scheme is preferable to voluntary implementation by the horticultural industry.