Buckthorn’s Prevalence in MPRB’s Park System
In Minnesota, Common buckthorn is an invasive shrub in Minneapolis parks that causes extensive damage to native plant populations, wildlife, pollinating insects, and adjacent water resources like streams and lakes through increased soil erosion. Common buckthorn is listed by the Minnesota Department of Agriculture as a Restricted Noxious Weed in Minnesota whose propagating parts may not be imported, sold, or transported in the state, except as allowed by permit under section 18.82. Noxious weeds that are designated as restricted and placed on the restricted list may be plants that are widely distributed in Minnesota and for which a requirement of eradication or control would not be feasible on a statewide basis using existing practices.
Within the MPRB system nearly every woodland that isn’t actively managed is impacted by buckthorn. It is ubiquitous both within our system as well as our region of the state. Furthermore, areas where buckthorn has been removed remain under constant pressure for reinvasion due to the prevalence of buckthorn on adjacent property. So long as there are fruiting buckthorn plants in adjacent properties, birds and other wildlife will transport the berries and seeds into the areas we have already restored.
Complete eradication of buckthorn system-wide would be a massive undertaking. Due to the fact that eradication on adjacent land is not within our control, the constant pressure of new buckthorn infestations means that this would not be a one-time expenditure or effort.
An ecosystem focused approach. How and when do we prioritize buckthorn control?
Natural Resources has focused our attention on a full restoration approach of identified management units (Managed Natural Areas). Buckthorn removal is often the first step in this restoration process. Equally important are the follow up actions that take place after its removal such as follow up control of buckthorn resprouts and the removal of other invasive species that become establish once buckthorn is removed. Reestablishment of native species helps to prevent reinvasion by buckthorn and other invasive species and is vital to making long term progress on restoration of individual management units.
Over-emphasis on buckthorn eradication across the whole Minneapolis Park system would cause our Natural Resources workgroup to become overextended and would result in lost restoration progress in our higher-quality Managed Natural Areas. By focusing our attention on specific management units and limiting the spread of buckthorn into those places, we protect the very valuable native plant communities found there and reduce the effort needed to protect them. In restoration biology, it is important to protect intact resources first, halting new invasions, and slowly working outwards into densely invaded areas. There are limited time and resources available and focusing only on buckthorn eradication opens us up to neglecting other high impact actions. By prioritizing our intact native plant communities in Managed Natural Areas, we are able to preserve the highest possible number of acres of natural area in the city with the lowest possible investment of time and money.
There are dozens of invasive species that impact our Natural Areas, many of which have statutory obligations for control that are more intensive than that of buckthorn. Buckthorn will always be one of the primary challenges we have in Natural Area restoration but is only one of the many challenges facing our Natural Areas.
Buckthorn’s removal will always be a primary, and often the initial step, in restoration efforts of Natural Areas, but it’s important to differentiate that the goal is restoration of theses Natural Areas and not just buckthorn eradication for its own sake. Prioritization of a single species above our greater goal of improving the quality of our Managed Natural Areas can lead to worse results overall.
For community members who want to play a role in buckthorn management in their neighborhood, MPRB offers Park Stewardship Agreements. Through stewardship agreements, volunteers can be outfitted with the tools and information they need to care for their local park and reduce invasive species populations. The success of these projects relies heavily on a multi-year approach to minimize the resurgence of sprouting and seeding buckthorn. MPRB staff will guide, advise, and provide assistance to Park Stewards to ensure their buckthorn removal objectives are realized. See our Garden and Natural Area Volunteers page for more information.
Management of natural areas primarily focuses on control of invasive and weedy plants to enhance native plant regeneration. Natural areas are managed with a variety of tools including prescribed burning and mowing.
Phase I (2017-2018) of the project consisted of developing a Geographical Information system (GIS) to map and categorize park natural areas by plant community type. An ecological quality ranking system for Minneapolis urban park system was also developed. The consultants presented a written