• Start-up
  • Planning
  • Action
  • Evaluation

The Apostle Islands National Lakeshore is planning for the long-term resilience of coastal wetlands on the islands by integrating climate change into infrastructure considerations, invasive species management, and the protection of rare species.

The coastal wetlands on the Apostle Islands National Lakeshore are managed in part for preservation. The team used the Adaptation Workbook and the Great Lakes coastal ecosystems adaptation menu of strategies and approaches to consider vulnerabilities from climate change, and to explore actions that may help managers cope with changes over time. Extreme hydrological fluctuations, warmer temperatures, and the projected loss of suitable habitat for keystone, specialized, and rare species may greatly disrupt wetland ecosystems and in particular peatlands by the end of the century.

Project Area

Apostle Islands National Lakeshore (image: Nasa Earth Observatory)
The Apostle Islands National Lakeshore is located in the sub-boreal region of Lake Superior where a significant number of plant species are at the southern edge of their range, while others are at the northern edge of their range. Coastal wetlands within the Apostle Islands currently maintain a diverse assemblage of unique species and have high floristic quality as compared to wetlands monitored across the Great Lakes Basin by the Coastal Wetland Monitoring Program. High floristic quality among Apostle Islands wetlands can be attributed to the relatively low abundance of invasive species cover, and fen and bog habitats that can support uniquely adapted species tolerant of relatively low pH and nutrient limitations.

The adjacency and connectivity to Lake Superior has direct effects and influences on Apostle Islands coastal wetland hydrology and nutrient dynamics. Apostle Islands coastal wetlands exhibit three types of connections to Lake Superior: 1) wetlands with semi-permanent sand barriers that exchange water through the barrier; 2) transient barriers that form and break multiple times throughout the year, occurring in response to rising wetland water levels that breach the barrier or when lake waves sufficiently erode the barrier; and 3) open connected wetlands that maintain a surface water connection throughout the year.

For the purposes of this adaptation planning discussion, only coastal wetlands (with or without a Sphagnum peat mat) were considered.

Management Goals

The Apostle Islands National Lakeshore is largely managed passively, therefore long-term management goals and objectives are more accurately stated as desired future conditions for ecosystems.

Desired future conditions:

  • The distribution and number of shore fens and similar wetland types remain stable or increase over time relative to current conditions.
  • Wetland structure, hydrology, geomorphology, and vegetation continue to function within a natural range of variation.
  • Rare, threatened, or endemic species occurrence and distribution at the habitat- and species-level remains stable over time. Communities maintain high floristic quality.

Given the protected status and diversity of coastal wetlands types in the Apostle Islands, these wetlands are well-positioned to serve as reference systems to study changes in wetland structure and function throughout the Great Lakes region.

Climate Change Impacts

For this project, the most important anticipated climate change impacts include:

  • Reduced suitable habitat for coastal peatland and fen species including rare and keystone species. Of the species observed in coastal and poor fen communities, 25% are projected to lose suitable habitat in Wisconsin by 2070 and up to one-half of the species are considered highly vulnerable to widespread changes in their ranges, including many species currently prominent among lakeshore wetlands.
  • Wetland barriers may be compromised by wave splash-over during periods of high lake level, more frequent strong storms, and less protective ice cover, which could damage sedge mats and lead to changes in water temperature, chemistry, and water level in coastal wetlands that may negatively affect the quality of coastal poor fens.
  • Invasion by non-native species, especially in a warming climate and in periods of low Lake Superior water levels.

*A variety of reports were used when assessing climate change vulnerability and risks. References to these resources can be found in this document

Challenges and Opportunities

Climate change will present challenges and opportunities for accomplishing the management objectives of this project, including:

Challenges

Uncertainty in how systems will respond to drastic fluctuations in Lake Superior water levels.
Rapid and sustained changes in water levels could alter physical characteristics of coastal sites and the composition, structure, and function of their wetland plant communities, in some cases losing systems altogether (barrier protected wetlands).
Increased nutrient influxes from more frequent and intense storm runoff combined with warmer temperatures may increase algal blooms, degrading water quality in the near shore and within coastal wetlands.
Invasive species colonization and growth may outpace the capacity needed to control them.
Increased wave heights and turbulence on the lake may reduce the number of seasonal travel opportunities to perform field work if conditions are unsafe to travel by boat.
Some coastal systems may be lost to more frequent and severe storms that intensify erosion and deteriorate sand barriers associated with interdunal swales.
Peatlands are unique and fragile ecosystems; if lost there may not be a restoration option.
If the Lake Superior water level regime diverges from its historic range, poor fen vegetation zones may contract while shore fen zones and emergent marsh may expand or transform away from sphagnum-dominated peatlands altogether.
Warmer conditions may cause heat stress in rare endemic plants.

Opportunities

A longer growing season or warmer shoulder seasons may extend the field season, and increase the time available to continue a species inventory, and invasive plant removal.
Spatial shifts or expansions in wetlands in response to climate change may contribute to a shifting mosaic of wetland communities over time that brings wetland communities to new locations.
Many coastal species, including rare species, have a long history of occurrence on the islands and may be able to cope with increasingly dynamic lake conditions.

Adaptation Actions

Project participants used the Adaptation Workbook and the draft menu of Great Lakes Coastal Adaptation Strategies and Approaches to develop several adaptation actions for this project, including:

Table outlining adaptation approaches and tactics

 

Monitoring

Project participants identified several monitoring items that could help inform future management, including:
Support the continued monitoring of long-term wetland transects and plots (both plant and hydrologic monitoring).
Continue monitoring rare or threatened and endangered plants and exotic species within the park.
Continue monitoring sandscapes and inventories of coastal features (such as aerial photos inventories), to monitor changes through time.
Document signs of visitor impacts including presence/absence of exotic species along common routes, width of trails, sandscape shape, and assessing for changes over time.
Use visitation statistics to assess changes in park use over time.

Learn More

To learn more about this project, contact
Danielle
.

Keywords

Coastal
Wetlands

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