Conservation and land management decisions often are based primarily on natural science, but could be more successful if human influences were effectively integrated into decision making. This is especially true for efforts to manage invasive plants, whose arrival is usually the product of deliberate human introduction. Risk-assessment models that predict the probability that a nonnative plant will naturalize or invade are useful tools for managing invasive plants. However, decisions based on such models could affect stakeholders differently. Careful assessment of risk-analysis methodologies should consider the importance of stakeholder participation. We surveyed the perceptions of four stakeholder groups (conservation professionals, master gardeners, professional horticulturists, and woodland landowners) in Iowa about invasive plants, general management approaches, and risk-assessment models. We also examined whether or not a stakeholder's nature relatedness plays a role in shaping his or her responses. Stakeholder perceptions varied less than expected across all four groups. Eighty-seven percent of respondents agreed invasive plants are a problem, and 88.4% agreed that we have a responsibility to manage them to protect natural areas. Support for the use of risk-assessment models also was high, with 78.7% of respondents agreeing that their use has potential to prevent plant invasions. Nature relatedness scores for all groups were correlated with respondent perspectives on invasive plants. Respondents believed biologically significant error rates (errors that might introduce a new invasive plant) should not exceed 5 to 10%. Respondents were more tolerant of horticulturally limiting errors (errors that restrict sale/use of a plant that would not have become invasive), reporting rates of 10 to 20% as acceptable. Researchers developing risk-assessment models might wish to aim for error rates within these bounds. General agreement among these stakeholder groups suggests potential support for future risk-management efforts related to invasive plants.
Management Implications: Many conservation professionals and land managers have spent countless hours containing or eradicating invasive plants encroaching on natural areas. Given the costs and effort associated with their control, prohibiting the introduction of new nonnative plants that are likely to become invasive would be very beneficial. Risk-assessment models are statistical tools that can be used to screen new plant introductions for invasiveness, but implementing these models comes with challenges. Because most new plant introductions are deliberately initiated by humans, stakeholders' needs must be taken into consideration if these pre-emptive management efforts are to be successful. We identified and surveyed four stakeholder groups (conservation professionals, master gardeners, professional horticulturists, and woodland landowners) in Iowa, who are important voices in decision-making for invasive plants, about their perspectives on general management approaches, and risk-assessment models. We also examined whether or not nature relatedness (a person's sense of connection to the natural world) plays a role in shaping these perspectives. We found these stakeholder groups had relatively minor differences of opinion. Stakeholders agreed that invasive plants were a problem that we have a responsibility to manage, and were open to the idea of passing state laws or mandates to achieve that goal. This was true even of professional horticulturists and master gardeners, who would potentially incur more costs than benefits from such regulations. Stakeholders also displayed consistently high levels of nature relatedness, and concern these groups have about invasive plants might be influenced by their identification with nature. Overall, our findings suggest that risk analysis to limit introduction of potentially invasive plants is l