The Ridges Sanctuary

Preservation, Education, and Research

Nature Notes: The Impact of Ice

by: Anna Foster


For Door County, the new year signals a return to ice in Green Bay and the cold days of January and February (and March, although we don’t want to admit it to ourselves just yet). The frozen landscape that the ice creates brings ice fishing, skating, cross country skiing, and snowmobiling to the forefront of outdoor activities. However, to the people who live here, the ice also indicates what the next summer season will bring.

Ice cover on the great lakes has varied greatly over the past 50 years. In 2021, the maximum ice cover was 33.3%, occurring during a polar front in mid-February. Variations in ice coverage can have both positive and negative consequences for residents of the great lakes and the ecosystems in which they live. For example, a polar vortex occurring in 2014 caused less water to evaporate over the winter and more significant snowmelt, which consequently led to water levels rising. In the summer of 2020, Lake Michigan's shoreline reached a record  high water level at 582 feet, 3 feet higher than its yearly average of 579 feet.

Maximum Ice Cover Percentage by Year for Lake Michigan Source: NOAA Great Lakes Environmental Resource Laboratory

When the maximum ice coverage is low during the winter, more lake water evaporation occurs, decreasing the water level. Many factors contribute to changing  ice cover and lake levels, and science suggests that these variations have become more severe over time. While the range of water levels remains the same in the hundred years over which they’ve been recorded, the cycling of water between high and low levels has become much more rapid over time. Scientists believe this trend of extremes will continue, although it seems that one thing is certain: Lake Michigan’s water levels are unpredictable.

How does ice affect The Ridges?

The swales of The Ridges are fed by groundwater and precipitation. While colder temperatures cause the swales to freeze for longer periods of time, Lake Michigan’s freeze percentage is not directly related to the swales. Perhaps the most impact that freezing water has is at the shoreline of The Ridges; the place where the landscape forms.

Ice is a key agent of erosion. The most obvious example of this is the effect that glaciers have had on Wisconsin's landscape. Glaciers have the power to transport materials, as well as carve the landscape beneath them. The freezing of Lake Michigan’s surface also erodes the landscape, albeit at a smaller scale.

As water levels in Lake Michigan increased to record breaking numbers in 2020, newly formed ridges along the shoreline washed away. Along with the ridges themselves, newly growing plant species were also lost. The dynamic nature of the ridges and swales is vulnerable to severe weather events and high and low lake levels.

Ridges that have taken a hundred years to form can be washed away in a single summer of storms. These events serve as a reminder that this fragile landscape is ever-changing. With Lake Michigan’s water cycles becoming more severe in recent years, it’s hard to say what new ridges and swales will look like, and how water levels will impact the boreal forest ecosystem.

Animal Adaptations on the Ice

A frozen swale at The Ridges Sanctuary

The inland swales of The Ridges freeze over in the winter, usually once the temperature drops below freezing for two or more consecutive days. Frozen swales force the sanctuary animals to adapt their behavior to survive in the cold weather.

Some hibernating animals, like turtles, remain underground or under the ice. The Painted turtle can survive in hypoxic (low oxygen) environments for months at a time. They survive by lowering their body temperature and metabolic activity. To survive in the hypoxic environment of an ice-covered swale, turtles process a chemical called glycogen. This allows them to survive but creates lactic acid as a byproduct. Painted turtles change their body chemistry to counteract the lactic acid and survive until they can absorb oxygen again.

The Wood frog doesn’t burrow in ponds like some other frog species. Instead, they chose to bury themselves in leaf litter and allow their bodies to freeze. They do this by producing a chemical similar to antifreeze in their cells, then push water out of their cells to survive. While the water freezes, their cells do not expand and burst, and they are able to thaw and hop away to vernal pools in the spring.

Muskrats, one of which we frequently see off our swale overlook by the entrance to Hidden Brook Boardwalk, will stay in their dens and venture underneath the ice until the surface of the swale thaws. In contrast, the river otter family that lives near our Hidden Brook Bridge frequently comes out of their den and explores the snowy ridges.

Animal Tracks on a frozen swale at The Ridges Sanctuary

Frozen swales also provide highways of travel for mammals of the sanctuary. Fresh snowfall is the perfect canvas for animal tracks. We frequently see snowshoe hare, deer, coyote, and otter tracks scampering across the ice in the sanctuary.

The best way to view wildlife on the frozen swales is via the snowshoe trail that leaves from our Cook-Fuller Nature Center. After a lovely hike along Sandy Swale, you can explore the quiet, rustic trails of the sanctuary. Snowshoes are available for rent from our nature center for $5 Wednesday through Sunday. To get an in-depth experience, join one of our winter guided hikes on Fridays at 1:30pm and Saturdays at 10:30am and 1:30pm this winter.



Great Lakes Integrated Sciences and Assessments. “Lake Levels.” GLISA: A NOAA RISA Team. NOAA, University of Michigan, Michigan State University, n.d.

Kelly, Mary Louise.  “Water Levels In The Great Lakes Approach A Record High.” NPR, June 16, 2020, sec. National.

US Department of Commerce, NOAA. “Ice Cover.” Accessed January 3, 2022.

“Water Level Data.” Accessed January 3, 2022.

Five Questions with Anna Foster, Environmental Interpreter

"I know I'm doing my job well when kids get into parents' cars and say 'Guess what we did today!"

We recently caught up with Anna Foster about her role as Environmental Interpreter and the "many hats" she wears at The Ridges!

How did you come to work at The Ridges?

I have been coming to Door County my whole life. My grandparents lived up in Ellison Bay, and I would spend the summers staying with them, riding my horses, and working at local businesses. The summer after my freshman year of college, I volunteered at The Ridges, working with the summer educators on summer camps. I was really interested in environmental education and was excited to gain experience in the field. In the spring of my sophomore year, I connected with staff there and learned about their summer internship opportunities. I was lucky enough to intern with The Ridges for two years. I was able to lead summer camps, work at the front desk, lead guided hikes, and work on interpretive signage.

After graduating from Lewis & Clark College with a BA in Environmental Studies, I came back to The Ridges as a year-round environmental interpreter. It’s been great to work with our interns for the past three years, helping them with their experience and realizing how much I’ve learned and grown since I was an intern. This summer marks my sixth year of summer camp there and the start of my third year as a staff member.

What do you do in your role as an Environmental Interpreter?

I wear many hats in my role. My main focus is to create educational opportunities - whether through events or signage – to connect people to our sanctuary. Educational programming is another part of my position. I help with our Dragonfly Nature Play program, run summer camps, work with middle school students at Gibraltar, and lead guided hikes. There’s never a dull moment!

What do you find to be most challenging about your job?

The most challenging part of my position is that everything is always changing. As with any small nonprofit, you have to expect the unexpected and step up when there’s no one else to do the job. A lot of the time, my workday consists entirely of things that are not in my Job Description. This can be especially difficult because our growing visitor base. We are always improvising and trying to create the best possible experience for every visitor. I think everyone at The Ridges does the work of at least two people, but we love what we do and can see the positive effect it has on our community!

What do you find to be the most rewarding?

Seeing someone’s face light up when they see a monarch butterfly hatch, watch pelicans fly overhead, learn the difference between a Red and a White pine, or notice a rare flower on the side of the trail. It’s rewarding to see the connections with The Ridges, or more broadly, nature. I see this most often in the children I work with. Many kids who participate in our summer camps or even our school year programming are uncomfortable outside when they first arrive. It’s inspiring to see them smiling while holding a garter snake or remembering what kind of tree they are sitting under. I know I’m doing my job well when kids get into their parents’ cars and say, “Guess what we did today!” I’m so glad I get to be the person who introduces them to all the cool things in nature, just as adults did with me when I was their age.

Another part of my job which is both important and exciting for me is trying to incorporate communities who are often underserved and excluded from environmental organizations, whether that be in the stories we tell or the opportunities we provide. For example, one aspect of The Ridges trail system that we have been trying to improve in the last few years is accessibility. Our newest boardwalk, finished in 2016, is ADA certified accessible for wheelchairs, walkers, and strollers. We have also tried testing tactile exhibit stations along our boardwalk that provide an experience for those who cannot read a traditional interpretive sign. We continue to seek out learning opportunities to make our organization a safe and accessible environment for everyone.

Do you have any advice to someone considering your career?

Working in the environmental nonprofit industry is difficult and requires sacrifice of personal time and energy. However, it’s an incredible opportunity to know that your work is making a positive difference, however small that may be. For example, I may lead a two-hour guided hike on any given morning. How big of a difference does that really make? If I can get someone in that hike group to appreciate why The Ridges is unique and worth protecting, that visitor might become a donor who will contribute to land acquisitions which will protect land for future generations. The more educational opportunities we can provide for the public, the better we are able to acquire, protect, and preserve land.

To anyone who wants to enter the environmental nonprofit industry, I would recommend starting at a small organization like The Ridges. I’ve been able to wear many different hats during my time here and learn skills that I never would have learned working for a large-scale, nationwide organization. Not only is it exciting to learn new things, but it’s great work experience for any future career opportunities. Not to mention, you’ll meet some of the most amazing ecologists, naturalists, experts, volunteers, and partners who work very hard to create positive changes in your community.


Meet Katie and Andy

In May 2021, The Ridges Sanctuary Board of Directors announced the appointment of our new senior leadership team, Andy Gill, Executive Director and Katie Krouse, Director of Operations. In this Q&A, Andy and Katie share thoughts about their roles and what they look forward to at the Ridges:


Tell us a bit about your backgrounds and how you came to the Ridges:

K: Nature has always been my safe place. A place where I could guarantee comfort and easily find a frog or bumble bee that would listen to my silly ideas. As I grew up, I dreamed about what I would be when I was older. At one point it was a veterinarian, at another point it was an evolutionary biologist, or a biological engineer or a geologic oceanographer. At every point in life, nature was at the core of my interests.

I was lucky enough to join the Ridges family in April of 2015. Due to a few serendipitous connections, I connected with the executive director (Steve) and land manager (Brian) of The Ridges Sanctuary. I didn’t know anything about Door County, or the oldest Land Trust in the state but was instantly hooked and offered a job on the spot. Little did they know I’d be sticking around a bit longer than expected.

My position has grown throughout the last 6.5 years. Running camp, leading hikes, working the front desk, heading out orchid trekking with Tony, and more has led to where I am today. These incredible opportunities to work in most areas of the organization have allowed me to confidently move into my new position of Director of Operations.

A: I grew up just west of Milwaukee. After graduating from the University of Wisconsin-Madison, I spent four years working in the Wisconsin Legislature where I staffed a State Representative from the Baraboo area. Following that valuable experience, I moved to Austin, TX where I took on the role of Executive Director with Pease Park Conservancy.

My wife Katie and I were married in Door County during the fall of 2017 and moved to the county in early 2018. I spent about three years helping Katie open her restaurant, Heirloom Café and Provisions, in Baileys Harbor. During that time, I also became President of the Baileys Harbor Community Association and Secretary of Horseshoe Bay Farms, Inc. Since moving to Door County, I have always had an admiration for Baileys Harbor and central to that was my appreciation for The Ridges.

My parents always encouraged my sisters and I to be outside, whether that was at home, visiting my grandparents, or at their cabin in the Northwoods. Through those experiences, I grew an appreciation for the leaders who exercised great foresight by protecting our most vulnerable natural resources. I knew The Ridges was going to be a special place for my family and I.

How do you work together as a team?

K: Together Andy and I have the opportunity to grow the organization in areas we hadn’t had the capacity to do otherwise. Together we can provide support to the rest of the incredible Ridges staff and ensure that our mission is the foundation of all our activities. While Andy has the opportunity to focus on long term growth, I have the opportunity to focus on our day-to-day activities that lay the foundation for long term growth.

A: Katie is an incredible asset to The Ridges. Not only is she an expert naturalist, but she knows how to tell the stories behind everything that makes The Ridges special. We make a strong team because Katie really delivers on maximizing the visitor experience. I know that our programs and events are going to be of the highest quality so I can focus on other parts of the organization and our mission. I think what makes us an effective team is that we are both good communicators who appreciate honest feedback and can receive feedback constructively. We both want each other to be successful because if that’s the case then The Ridges is better off.

What challenges do you face?

K: On of the biggest challenges I will face is constantly comparing the present and future to the past. It will be important to recognize that The Ridges has evolved and comes out of the pandemic as a strong and empowered organization. People’s priorities have evolved, and we are seeing more individuals that wouldn’t normally hike trails, visiting the Sanctuary. We have the opportunity to educate more individuals now more than ever on the importance of preservation and stewardship.

A: The biggest challenge I see is how we meet the demand for our programs while remaining true the leaders that established this magical place. The history and culture around The Ridges will always be at the forefront, but the reality is Door County is changing – so how do we carry on the legacy of The Ridges while also overcoming the modern-day (and future) challenges?

What are you most excited about for the coming year?

K: I am most excited to take what we have learned over the last year and a half and deliver our mission through incredible programs. Through education and programs designed for individuals from age ‘walking’ to 100, we have the greatest opportunity to expand our experience to deliver our mission. One example is our Festival of Nature. In 2020, we rescheduled then cancelled the Festival, which pushed us to redesign the experience in 2021. Because of what we learned, we can enter 2022 with an even more robust and expanded Festival of Nature experience.

A: I am excited to see where we can take this organization. There is still so much potential to further our mission of education, outreach, and research as demand and support continue to grow. While it’s critical that we continue to preserve land where possible, I am increasingly motivated by where we can take our education, outreach, and research efforts. In my short time at The Ridges, I have seen how we play an important role in inspiring the next generation of conservationists.

What else should we know about you?

K: Being a part of The Ridges is truly a very special part of my life. I wake up excited to go to work and go home at the end of the day proud of the work we accomplished and ready to do it all over again the next morning. The hardest part about getting myself moving and to work is having to leave my furry friends at home. But never fear, my furry friends make sure we spend almost every waking minute outside. Hiking, visiting the dog park, or simply sitting on the front porch with my fifth cup of coffee for the day and a good book are where you will find me when I’m not at the office.

A: Right now, my life is consumed by being an expecting dad. My wife Katie and I are expecting our first child in October and are thrilled to begin that next adventure together. We like to spend time travelling and creating new experiences. In Door County, we keep it simple – lots of bike riding, time on the water, walking our dog Jerri Garcia Gill, and spending time with friends.

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