Walking Tree Travel History

Walking Tree was founded in 2005 by three childhood friends from Denver, Colorado who all came to share the belief in the transformative power of travel after years of working and volunteering abroad. Since our first program in 2006 traveling with 12 students to Costa Rica, we have run programs in over 18 countries worldwide with thousands of students from over 500 high schools in 46 states and nine countries. Despite this growth, our mission of creating authentic programs that inspire our travelers to become global leaders remains at the heart of all of our programming.

Our Team Today

Our team is made up of truly exceptional individuals who are committed to guiding the next generation of global leaders. Our international staff has an intimate understanding of the local environment, language and culture of our host destinations, helping to ensure that our adventures are as smooth, safe, and authentic as possible. Our Program Leaders have traveled extensively and hail from the world’s top colleges and universities. They are extraordinary guides, teachers, mentors and friends. Read more about who we are below!

By the Numbers…


First Aid and CPR certified


Have worked for non-profits


Have worked in higher education


Have worked in K-12 education


Languages Spoken


Countries Visited


Age Started Traveling

Who We Are

Becca Sheffield

Marketing and Program Management

Colorado State University - B.A. Communication Studies and Spanish
Middlebury Institute of International Studies - M.A. International Education Management

After her first study abroad experience in Lima, Peru in college, Becca knew she had found her passion for helping others have meaningful experiences across cultures. After teaching Spanish to learners of all ages and working in the non-profit sector, Becca decided to pursue her Master’s degree in International Education Management from the Middlebury Institute of International Studies at Monterey. Now she is pursuing her dream of helping students have incredible experiences abroad, when she isn’t hiking, salsa dancing, or quoting movie lines.

Gabriel Duncan

Co-Founder of Walking Tree Travel and Business Lead

Colby College - B.A. International Relations and Government

While at Colby, Gabriel spent a semester in Spain at the University of Salamanca studying contemporary Spanish politics and Spanish language. He also lettered for four-years on Colby’s lacrosse team and earned All-American honors. After graduating, Gabriel hit the road. He fished commercially in Alaska, taught in Chile and China, led programs for students in Spain and Costa Rica, and traveled to over 50 countries and all 50 states in the USA. Regardless of where Gabriel is located, he is constantly haunted by his naive faith in and unconditional love for Denver sports teams.

Jordan Sparrow

Country Operations Director

University of Kansas - B.A. Latin American Studies; Global and International Studies, Minor in Brazilian Studies

Jordan is a Midwesterner at heart, born and raised in Kansas City.  He spent his first summer after high school in Guatemala where he began learning Spanish and cultivated a deep interest in everything Latin America.  In college, Jordan spent almost half of his university career studying abroad in both Costa Rica and Brazil.  During that time, he mastered language skills in both Spanish and Portuguese, spent a lot of time at the beach and met the love of his life in Costa Rica. After college, he moved to Costa Rica where he taught Portuguese to Costa Ricans and began his career in student travel.  After almost six years of living in Costa Rica, Jordan, his partner and their two dogs moved to Denver where they currently live.  As with the rest of the SSA team, Jordan has traveled extensively throughout Latin America, the Caribbean and Southeast Asia.  Jordan is passionate about languages, history, social justice and eating great food.

Lacey Merkel

Admissions Director

University of Arizona - B.S. in Spanish and Portuguese, Minor in Business

Lacey is originally from Flagstaff, Arizona but has been spending her summers in Denver since she was a kid. Originally a business major, she decided to spend her sophomore year studying in Viña Del Mar, Chile. This is where she truly found her passion for travel and learning about other cultures. When she returned to Arizona, she changed her focus to learning Spanish and Portuguese and decided to pursue her TEFL certificate. After graduation, Lacey moved to Fortaleza, Brazil and taught English to high school students, pilots and doctors. She then moved to Denver and continued teaching English. In her free time she enjoys live music, snowboarding, traveling and of course eating amazing “hole-in-the-wall” food.

Luke Mueller

Co-Founder of Walking Tree Travel and Business Lead

Emory University - B.A. Sociology and minor in Latin American History

During college, Luke spent a semester living and traveling in rural Mexico. His experience sparked a fascination with Latin America and a commitment to community service that continues to this day. Upon graduating from college, he joined WorldTeach and lived with a local family in a small village in Costa Rica while teaching elementary English. After this experience, he moved to San José, the capital and largest city, and wrote for The Tico Times newspaper. Now settled in Denver, he continues to crave massive helpings of rice and beans. Luke has traveled to 60+ countries on five continents and is fluent in Spanish.

Morrison Mast

Conservation Program Director

College of William and Mary - B.S. Biology and Environmental Science & Policy

Morrison is an obsessive and experienced traveler, having been to 50+ countries in pursuit of the life-changing experiences offered by the wild places of the world. Fluent in Portuguese, Spanish, and broken French, he is an avid wildlife photographer whose favorite subjects are beetles, spiders, and the oft overlooked microcosms they inhabit. Morrison is a percussionist at heart and has performed nationally and internationally with groups ranging in style from symphonic to experimental rock and traditional Turkish music. During his undergraduate years, Morrison conducted research in Brazil and Madagascar with conservation organizations that are actively working with communities to strike a sustainable balance between humans and the ecosystems that support them. Education is surely the most rewarding aspect of his work; Morrison constantly strives to inspire positive change by communicating his overwhelming awe of the natural world to others. Morrison hopes to build a career in biodiversity conservation and is currently in charge of developing and implementing new Conservation Expeditions.

Nicole Kirchner

Educational Partnerships

West Chester University-B.S. Elementary Education, Minor in History. School for International Training (SIT)-M.A. International Education

Nicole grew up in Lancaster, Pennsylvania, also known as Amish country, and has always been accustomed to seeing a culture unlike her own. Ever since her first international experience at 4 years old, she has been intrigued by exploring foreign places. It was a summer abroad course in London, that Nicole looked at the in-country director and thought one-day that will be her. After graduation, she worked for 3 years at an inner-city, public school until she decided a change was needed. Without hesitation, Nicole moved to Cusco, Peru where she obtained her TEFL Certification and taught English for one year at a local intercultural center. Recognizing the value and impact intercultural experiences have, she returned to the US to obtain her Masters Degree in International Education. She then interned with a nonprofit organization in Haiti as their Educational Coordinator and backpacked through Central America to strengthen her second language skill of Spanish. Nicole currently lives in Antigua, Guatemala, along with her adopted dog Timo, where she teaches Middle School Language Arts and is the Service Learning Coordinator for a K-12 private school. One of her most memorable travel experiences was when she worked in the Galapagos Islands, immersed in nature, and spent her summer swimming with the sea lions, sea turtles, and marine iguanas.

Paul Laurie

Co-Founder of Walking Tree Travel and Business Lead

Santa Clara University - B.A. Marketing and International Business

Santa Clara University – B.A. Marketing and International Business

During college, Paul spent a semester abroad studying Spanish and European Commerce in Madrid, Spain. After graduation, he embarked on a three-year journey that took him all over the world. He traveled from Times Square to Tierra del Fuego and from Siberia to Singapore, enjoying distinct cultures, great food and meeting lifelong friends every step of the way. Among other positions, Paul worked as a fashion photographer and on Wall Street before returning to his real passion for student travel. Paul has traveled to 80+countries in pursuit of the best meal under $5 and making additions to his antique globe collection.

Sara Lavell

Costa Rica Country Director

Universidad de Costa Rica – B.Sc. Geography

Proudly born a ''tica'' with a British father and a Panamanian mother, Sara was raised in the Caribbean coast of Costa Rica. Sara started traveling the world at a young age and has visited 4 continents. Passionate about conservation, sustainable development and education Sara spent her college years volunteering in different communities during mid-term vacations and later found herself sharing some of her interests with US students and volunteers traveling all over Central America. Nowadays, Sara is finishing her master’s degree in Planning with an emphasis on Socioeconomic Project Management. When she is not busy you can find her spending time outdoors, reading, laughing with her friends or cooking with her family.

Tommy Tyson

Latin America Operations

University of Denver - B.A. Spanish, Minors in History and Hebrew

Tommy graduated from the University of Denver. His hobbies include camping, basketball, studying history, traveling, and learning languages. He is fluent in Spanish, and also speaks Hebrew as well. He first developed his love of languages and Latin American culture at the age of ten on a mission trip in Mexico. This experience and the subsequent trips to follow inspired him to study Spanish in school, and to pursue more development work in other areas of Latin America as well. During a semester abroad in college in Cusco, Peru, Tommy had the pleasure of working alongside ProWorld Peru in rural communities like Ocurruro, Urubamba and Ollantaytambo. Tommy also has spent time building houses in El Salvador with Habitat for Humanity. He now lives in Cusco, Peru full time!

Yusra Saleh


Earlham College - B.A. Peace & Global Studies 
Indiana University - M.P.A. International Development and Nonprofit Management

Born and raised in Kuwait, Yusra traveled to the United States to pursue a B.A. in Peace and Global Studies at Earlham College with a focus on Conflict Transformation. Since then, she has been involved in several leadership positions (including working for a start- up peace museum) and actively seeks to help individuals challenge and learn from the world around them. Growing up in a household with a Father who was a Pilot and a Mother who was a Flight Attendant, Yusra began traveling as soon as she could walk and enjoys engaging the world through travel and interaction. She is passionate about social justice issues, grassroots movements and individual empowerment. In her free time, Yusra enjoys exploring new cities by bike, drawing and getting lost in libraries and bookstores.