Nicollet Island

Nicollet Island, before prairie restoration

This location on Nicollet Island may not look like much, yet. Soon this area will be converted to a diverse mix of beautiful native prairie plants, providing much-needed resources for local pollinators and aesthetic beauty for island residents and visitors.

FMR is embarking on restoration of the natural areas on Nicollet Island. Restoration will encompass roughly 5.8 acres of land on the northeast side of the island and a band of an additional 1.3 acres of land on the island’s west side. The island itself is a 48-acre landmass located in the Mississippi River in Minneapolis. The acres in question are all owned by the Minneapolis Park and Recreation Board.

While natural vegetation has recovered since the height of industrial development in the late 1800s, other threats to these natural areas remain. The open spaces within the project area have experienced continual woody encroachment in recent decades, both by native and non-native shrubs and trees. Runoff from increased impervious surfaces has caused gully formation at points along the slope. Existing conditions show evidence of much disturbance to the site, including earth moving, trails, yard waste, encroachment, and a proliferation and dominance of non-native vegetation.

Driven by a lack of natural ecosystems in the urban matrix, and by degradation from invasive species and other land use practices, FMR is pursuing restoration of native plant communities on the upland areas of the site. This plan focuses on restoration of forest and prairie communities, which are targeted by the MN DNR as being among the most in need of restoration in this ecological subsection (Anoka Sand Plain).

Site History

Prior to European settlement, the island was a mix of habitat types and pre-settlement vegetation was identified as ‘oak openings and barrens’ or oak savanna. However, firsthand records of vegetation on the island include dense oak-maple forests and open grassland areas. While this is different from the predominant surrounding vegetation, the island’s position in the Mississippi River would have shielded it from the historical fire regime, allowing areas of denser forest to develop. Much of the natural area on the island has since been lost to development, and today the island itself and the areas directly around the island now make up portions of downtown and Northeast Minneapolis, highlighting the historical conversion of natural areas for the rapidly expanding Minneapolis metro area.

Current Conditions and Assessment

A natural resource inventory and assessment was conducted by staff from Friends of the Mississippi River in the summer and fall of 2017, and a natural resources management plan (NRMP) was written and adopted in early 2018. The property consists of three primary areas: altered deciduous woodlands, a degraded grassland, and turfgrass. The forested areas are dominated by box elder, hackberry, and green ash. American elm, cottonwood, and Siberian elm are prevalent as well. Buckthorn dominates much of the shrub layer, though few uninvaded pockets remain. White mulberry, a non-native tree, is becoming dominant in some patches. Garlic mustard, burdock, motherwort, and other herbaceous invaders are patchy but present. Groundcover in the forested areas ranges from thin to fairly dense, with species like white snakeroot, Enchanter’s nightshade, Virginia stickseed. The shortgrass unit is severely degraded; smooth brome and Kentucky bluegrass dominate, while few native grasses or forbs are present. Patches of reed canary grass, birdsfoot trefoil and spotted knapweed are present throughout. Woody species are also invading this area, which will transition to a non-native dominated woodland if left unchecked.

The property has many areas that have been clearly impacted by human uses, including the ‘not-a-lot’ area most recently used as a parking lot. Use of the property by island residents has also degraded the landscape, with the remaining forest areas serving as a historical source of firewood for residents and now an area to dump yard waste. However, restoration of the grassland area just north of the high school (not included in the project area) occurred in the early 2000s. Unfortunately, without maintenance, this area has become degraded and overgrown with native and non-native trees. The rest of the property is highly degraded, both in terms of species composition and in the presence of non-native, invasive species. A lack of much-needed fire has allowed woody species – both native and non-native – to become overabundant and has allowed herbaceous invaders to proliferate.

Invasive plant species are the largest threat to the health of the natural areas on the island. Woody invaders in particular have degraded the plant communities in the units. Other non-native herbaceous species are present in both the forests and grasslands. Another potential management issue is erosion in the forested areas. Natural overland flow has increased due to nearby development and impervious surfaces, and combined with a lack of deep-rooted vegetation, has led to areas of serious erosion. While this will be somewhat mitigated by the addition of native vegetation, it should be given extra consideration if time and budget allows. Finally, future issues should be considered as well. For example, the large contingent of ash trees on the property is at risk from the emerald ash borer. Understanding these risks and their likelihoods can help in the design and preparation of future management strategies.

Restoration

Based on the natural resource inventory and assessment, the lack of past management activities, the property’s connection with nearby natural areas, as well as general goals by the Minnesota Department of Natural Resources for this landscape, the NRMP recommends removing invasive species and restoring native forest and prairie plant communities on the site.

Restoration is divided into three phases. The first phase focuses on removal of non-native woody shrubs and trees from all units, concentrating first on the forested units. Diversity should be added to forested areas as invaders are removed through both seeding and planting in all vegetative strata. Inclusion of climate-adapted tree species will be a priority for revegetation. As time and budget allows, overabundant native woody species should be thinned in the forested units, including but not limited to green ash and sumac. Removal should be conducted in the fall and winter, and may be done through a combination of cutting and treating and brush mowing in certain less sensitive areas. Follow-up treatment in subsequent years will focus on treating re-sprouts and newly emerged seedlings.

The second phase focuses on the restoration of prairie habitat on the grassland and not-a-lot units. This will consist of removing native and non-native shrubs and trees that are encroaching on the units, preparing the units for seeding through a combination of herbaceous vegetation removal, soil tilling, and prescribed fire, and broadcast seeding with a diverse mix of native prairie species. Follow-up maintenance will include spot spraying and hand pulling problem invasive species, regular mows, and eventual prescribed burns on the not-a-lot unit. The shortgrass unit on the north tip of the island will eventually be transitioned to a maple-dominated forest reminiscent of historical communities, and will include a mix of climate adapted tree species.

The third phase focuses on erosion control in the forested units. Seeding and planting the woodland units with appropriate native shrubs and understory plants will help to stymie erosion and add structural diversity to the site. Other recommended erosion control methods include installation of natural erosion bars, installation of grass strips and erosion mats, and soil work to prevent and remediate gully formation.

Partnership and funding

Funding for the natural resources management planning was obtained through a planning grant from the Mississippi Watershed Management Organization (MWMO). Initial restoration will begin in fall 2018 and is funded by the National Fish and Wildlife Foundation and an MWMO action grant. Partners for the project include the MPRB, MWMO, Friends of the Riverfront, and the Nicollet Island East Bank Neighborhood Association.

Get involved

To receive notice of future Nicollet Island and Above the Falls area restoration events, contact FMR Volunteer Coordinator Amy Kilgore at akilgore@fmr.org. Or, visit our Events Calendar for our most up-to-date listing of upcoming events. To receive a twice-a-month e-newsletter including all FMR activities and news, sign up for Mississippi Messages.