KALAMAZOO, MI — On a cold, dark, and blustery evening, as fat, wet snowflakes fel outside, approximately 20 people braved the weather to come to listen to
Dr. Tiffany Schriever, freshwater ecologist and Associate Professor in the Department of Biological Sciences and School of Environment, Geography, and Sustainability at Western Michigan University, discuss her research on interdunal wetlands at People’s Church.
Sponsored by the Southwestern Chapter of the Michigan Botanical Society, Schriever's talk focused on the wetlands nestled between Michigan’s sky-high dunes and thick forests.
Before starting, she asked the audience to close their eyes and imagine their favorite Michigan beach — prompting people to “feel that warm sand on the soles of your feet… the breeze off the lake hit your face, blow your hair-, hearing kids play around in the sand and waves crashing against the beach.” After the warm thoughts inspired by this visualization exercise, Schriever began her discussion.
What are interdunal wetlands?
Interdunal wetlands are part of the “largest freshwater dune system in the world,” stretching along the coastline of Lake Michigan, Lake Huron, and parts of Lake Superior. They form “between beach ridges and behind the dunes, within dune depressions,” connected via groundwater to the nearest Great Lake. Examples are found at Ludington State Park, Saugatuck Harbor Natural Area, and Warren Dunes State Park, among others.
Schriever added that these wetland systems are “globally imperiled… due to their rarity and their very limited distribution,” suffering from both “natural fragmentation,” and anthropogenic fragmentation caused by development. Research into these systems is limited, focusing mainly on vegetation or geology rather than animal communities.
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A photo of an interdunal wetlandSchriever’s research is groundbreaking, as she and her student team, have begun exploring the animal life of these wetlands. One student’s thesis cataloged dragonflies and damselflies at Saugatuck Harbor Natural Area, “because there was no known list of species in these wetlands.” They found that “40% of all the known dragonflies and damselflies in the state were found just in this one wetland complex” and added “five new county records of dragonflies and damselflies.”
This diversity in such an isolated area led Schriever to consider broader diversity across Lake Michigan’s interdunal wetlands. The vast coastline, which spans over 4.5 degrees of latitude, causes significant variations in temperature and precipitation. Typically, diversity increases the closer you get to the equator, a pattern Schriever and her team sought to explore in the interdunal wetlands, using “the latitudinal gradient of Lake Michigan to test whether diversity is higher in Southern Michigan or Northern Michigan.”
On the dunes, the further away from the shoreline, the more vegetation appears. Because there is less shade covering interdunal wetlands, there’s more solar radiation, meaning there are fewer available resources for organisms than for those in more shaded wetlands. This results in variations in species composition.
Research reveals species turnover
Schriever and her students collected and analyzed macroinvertebrates along the Lake Michigan coastline, examining species diversity at places like Ludington State Park. She notes, “We can use different environmental data and correlate that to diversity metrics,” while beta diversity, or the “measure of compositional change from one wetland to another,” is most important.
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Dr. Tiffany Schriever, a freshwater ecologist and WMU Associate Professor, in wetlands in AustraliaBeta diversity highlights how wetland communities differ in species and abundance, such as when one community is a subset of another or when a species is replaced with a different one. Schriever’s research reveals significant species turnover. For example, “between Indiana Dunes and Sleeping Bear Dunes, you see 77% change in the species composition that are in those wetlands.” It also indicates “very big changes in the species that are in these wetlands — at short distances as well as really big distances.”
Interdunal wetlands have more “micro predators like the phantom Midge (and) micro caddisflies,” but fewer mosquitos than forested wetlands. The research also cataloged the amphibian and reptile diversity, which “was also not recorded very well from interdunal wetlands.” Schriever and her team “documented the breeding of Fowler's Toad, which is a Michigan species of special concern.”
Wetlands within a park or preserve boundaries are protected. If an interdunal wetland is within 1000 meters of a Great Lake, it is protected under the
Geomare-Anderson Wetlands Protection Act, 1979, Part 303. However, some are much farther than 1000 meters and remain unprotected for various reasons.
Development poses the greatest threat
When asked what’s the greatest, immediate threat, Schriever cited development, “because you take away the dunes… and then you all of a sudden [you] change the hydrology to make a new wetland, or to keep that wetland there.” If a dune is destroyed, it's not just sand that’s removed; the entire “landscape which enables the formation and persistence of wetlands and the animals and plants of that dune system” changes.
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Tiffany Schriever, a freshwater ecologist and WMU Associate Professor., spoke recently at People's ChurchSchriever concluded the talk by asking the audience to “be able to step away just from the lake for a little bit and look beyond you and look back in the dunes and see the massive diversity that we have out there because it's not going to be there forever.”
For more information on Schriever’s research, please visit her research
webpage.