Research themes

Strategic and tactical decisions for the statewide management of terrestrial invasive species depend on accurate, detailed information about the geographic distribution of those species.

Currently, many agencies and organizations in Minnesota are gathering information about the distribution of terrestrial invasive species to support internal decision-making. There is a growing recognition of the value of sharing information about the distribution of invasive plants and pests more broadly. Some tools already exist for this purpose. For example, EDDMapS (www.eddmaps.org) has been used as a clearinghouse for terrestrial invasive plant data for some state agencies. Such tools are useful for collecting presence points but do not “connect the dots” to show the complete, potential distribution of an invasive plant or pest. Maps that depict where terrestrial invasive species are present and abundant across the state are essential to coordinate regional terrestrial invasive species management plans and to evaluate the effectiveness of the activities conducted under those plans. 

Some terrestrial invasive species may not be reliably detected with typical approaches. Ground-based surveys are time and resource-intensive and are frequently limited to relatively small areas. Aerial surveys for widespread woody species, such as buckthorn, have been attempted but have yielded too many false positives to be useful. New approaches to reliably detect and identify priority species are needed.

Temperature and moisture conditions, land use patterns, and global trade activity in Minnesota have been changing over the past 100 years and are projected to continue to change. Each of these future conditions can directly or indirectly affect the distribution, abundance, and/or impact of terrestrial invasive species that are already present or might arrive in the state. Tools are needed to describe which terrestrial invasive species are likely to become more widespread, abundant, or damaging and which are likely to experience geographic range contractions, become less abundant, or have less impact in the next 30–100 years. These descriptions should be as spatially explicit as possible.

A variety of cultural, physical, mechanical, biological and chemical approaches are being used alone and in combinations to control terrestrial invasive species in Minnesota. Invasive species managers face a two-part challenge when choosing a course of action.

First, managers must contend with difficult questions about what constitutes successful management. For example, while the timely application of appropriate herbicides is likely to kill targeted plants, is the treatment “successful” if seeds are so plentiful that the plant readily re-establishes itself in the following year or if the composition of the plant community does not “improve”? Similarly, at what time- or spatial-scale should management be considered successful, for example, only within the treated area or over the entire range of the plant within the state?

Second, managers frequently have little information about the effectiveness of novel management tactics. For example, the use of large grazing animals (e.g., sheep, goats, and cattle) increasingly is proposed as a strategy for invasive plant management, yet reliable information about the effectiveness of generalist grazers is limited. New control options are needed, and their effectiveness rigorously evaluated, to ensure management goals are being met.

Socio-economic factors and human dimensions play a major role in the likelihood of new species arriving, the effectiveness of management strategies, factors motivating landowners and others to implement management strategies, and the consequences of new invasions. Research is needed to identify and measure the strength (i.e., propagule pressure) of different human-mediated pathways that might bring new species to Minnesota. This research will inform regulatory decisions to help prevent the arrival of new species and direct early-detection surveys to areas where initial introductions are most likely. 

In addition, decision-support tools are needed to determine the relative effectiveness of eradication, containment, or suppression strategies under various conditions, while accounting for uncertainties in our knowledge about an invading species and/or its response to management. 

More information is needed about the effectiveness of various educational, regulatory, economic, or other interventions to promote the implementation of management treatments by landowners. In other words, once effective treatment options are identified, what strategies are most effective to promote their implementation by landowners? Hypothesis-driven research is needed to understand what motivates landowners to invest in treatments individually or through partnerships. 

Finally, the economic impacts from invasive species frequently depend on micro- and macroeconomic forces and often dictate the appropriate level of investment in a management response. Research is needed to better characterize the realized and potential economic impacts of invasive species in Minnesota and to incorporate this information and associated uncertainties into scalable budgeting tools for management decisions.