Award-winning journalist Amy Martin has spent years tuning into nature’s hidden soundtrack. As the host and creator of Threshold, she explores the intricate ways life communicates beyond human perception. In its latest season, Hark, Amy uncovers how species from birds to dolphins—and even turtles—use sound to share information we’re only beginning to understand. Thanks to breakthroughs in acoustic research, these conversations are finally coming into focus.

Wasfia Nazreen is a Bangladeshi mountaineer and human rights advocate known for blending adventure with activism. She is the first Bangladeshi to climb the Seven Summits and the only Bengali to summit K2, one of the world’s most dangerous peaks. Her expeditions serve as spiritual practice and a platform for women’s rights in Bangladesh, earning her National Geographic’s Adventurer of the Year in 2014.

Eric Larsen is a pioneering polar explorer who completed the first-ever summer expedition to the North Pole, navigating thin, unstable sea ice and miles of open water. In 2010, he became the first person to reach both poles and summit Mount Everest within a single year. With decades of experience crossing the Arctic Ocean and Antarctic ice sheet, Eric has become a trusted resource and guide for aspiring polar adventurers.

Jennifer Britz is a trail runner based in Bar Harbor, Maine. She spends half the year on Acadia National Park’s rugged trails and the other half perfecting her craft on lightweight running snowshoes built for speed. Over the past decade, Britz has dedicated herself to mastering this niche sport, pushing her limits across varied terrain. In 2022, she earned gold at the World Snowshoe Championships in Argentina.

Emily Pennington is an REI gear tester and outdoor expert who knows what makes equipment worth the investment. In this holiday gift guide episode, she shares her top picks for the best outdoor gear gifts—whether it’s backpacking essentials, ski gear for hitting the slopes, or running gear for everyday adventures. Emily breaks down what matters most when choosing quality gear that lasts, so you can give gifts that the adventurers in your life will love.

Tyler Turner has always been a bit of a daredevil. He grew up skiing, snowboarding, and eventually became a skydiving instructor. After a 2015 accident resulted in the amputation of both legs, he rebuilt his life around the sports he loves. Today, he’s a three-time Para Snowboard Cross World Champion, a Paralympic gold medalist, and the first bilateral amputee to fly in a wingsuit.

Barrington Scott is a record-holding scuba diver who has spent the last decade exploring the underwater world through snorkeling, scuba, and freediving. He’s lived in coastal towns around the globe, diving as often as possible and immersing himself in coral reefs, sea caves, and marine life. In 2024, Barrington set a Guinness World Record for scuba diving on all seven continents.

Chad Caruso kicked off his wild idea in Venice Beach, California, with a skateboard and a goal: to cross the country on four wheels. Over 57 days, he pushed through deserts, mountain ranges, and extreme weather, ultimately landing in Virginia Beach, Virginia and setting a Guinness World Record for the fastest coast-to-coast skateboarding journey.

Alex Hutchinson is a science journalist who explores how technology is reshaping the way we experience the outdoors. While apps can guide us to trailheads and campsites, they can also strip away the thrill of the unexpected. In his recent book, The Explorer’s Gene, Alex blends stories of adventure with insights from psychology and neuroscience to show how breaking routine and embracing the unknown can lead to a more meaningful, fun, and productive life.

In October 2024, Tracee Metcalfe became the first American woman to climb all 14 of the world’s tallest mountains, each towering above 8,000 meters. Her journey demanded years of preparation and survival in some of the most unforgiving conditions—from the deadly slopes of Annapurna to the steep walls of K2.

Jacob Lemanski is a long distance cyclist who embarked on a global journey in 2013 with no set destination, just a desire to see how far his legs could take him. Over two and a half years, he pedaled more than 38,000 miles across 42 countries, driven by curiosity, endurance, and a love for exploration.

Nelly Attar has climbed more than 30 notable peaks around the world, including Mount Everest. Her journey to these intense mountaineering expeditions had an unconventional origin: dance. She grew up learning choreography from YouTube and later opened Saudi Arabia’s first dance studio. As she explored movement through fitness, weightlifting, and hiking, she built the foundation for high-altitude endurance. In 2022, Nelly became the first Arab to summit K2.

Ron Griswell is an outdoor educator and founder of HBCU's Outside, a nonprofit dedicated to connecting students at historically Black colleges and universities with nature. After taking a gap year from North Carolina A&T State University to work as an adventure guide, Ron discovered a deeper purpose in the outdoors. Motivated by the lack of outdoor opportunities at his HBCU, he launched a movement to make nature more accessible and inclusive. His work continues to inspire the next generation of outdoor leaders.

Rickey Gates is a professional athlete and endurance runner known for redefining what it means to explore on foot. After racing at an elite level, he ran 3,700 miles across America and later completed every street in San Francisco. Nearly seven years later, Rickey is tackling his latest challenge: identifying and running 50 Classic Trails across North America. His adventures go beyond distance—they are a way for him to explore, connect, and see the world in a whole new light.

Nadah Feteih spent years working as a software engineer before discovering a deep passion for the outdoors. As she ventured into running, trekking, and mountaineering, she often found herself as the only woman wearing a hijab on the trail. That experience led Nadah to found Ma'wa Collective, an adventure company dedicated to creating space for Muslim women in the outdoors.

Dorian Anderson was a neuroscientist and geneticist with a promising academic career when he made a radical shift: in 2014, he left the lab to pursue a year-long, cross-country birding adventure—on a bicycle. Pedaling nearly 18,000 miles across the U.S., his goal was to spot over 600 bird species while deepening his sobriety, and reconnecting with nature.

Jeska Clark is a human performance specialist who studies how people adapt to extreme environments such as high-altitude peaks, sub-zero temperatures, and the intense pressure of deep ocean dives. Her research combines scientific inquiry with personal experience, as she applies insights from her academic work to her own wilderness expeditions. A skilled outdoorswoman, Jeska has completed several ambitious treks and is now preparing to lead the first all Black team to the North Pole.

Marlene and Dan Lin have been living on the road full-time for the past 17 years. Alongside their three children and two cats, they’ve driven across the U.S. multiple times, explored over 30 countries in Europe, and road-tripped from California to Patagonia via the Pan-American Highway. What began as a short-term adventure turned into a lifestyle they never anticipated—nearly two decades of life in a camper van.

Libby DeLana began walking every day at age 50, while juggling her role as co-founder of an ad agency and parenting two teenage boys. What started as a one-month experiment became a 13-year streak of daily walks. Alongside walking, Libby embraced cold plunging as a way to reset her mind and body. These rituals helped her reinvent herself as an author, podcast host, model, and inspiration for others seeking clarity and transformation through movement.

Albert Lin is a renowned explorer, scientist, and storyteller. He is best known for his role as the host of multiple National Geographic programs. Together with his team, he uses advanced technologies such as satellites, drones, ground penetrating radar, and cutting edge LiDAR to uncover ancient civilizations around the world.