I am surprised that after several years in this profession, including many hours of solo reflective time and writing about my thoughts and feelings, I had never been asked this question. And so, largely for my own peace of mind, here is a more thoroughly thought out and unsurprised response:
Several years ago, someone told me about an old wise man, who said that only two things make people happy. One is connection with other people, and the other is connection with nature. Since then, my understanding has become that people ARE nature, or at least an essential part of it, but that many of us have lost that connection and understanding.
Outdoor and experiential education is important because it re-connects children to the natural world that they are a part of. In a time when video games, TV and facebook are the icons of kids lives, it becomes increasingly difficult for kids to care about what is going on "away from the power outlets." Not only does being in the outdoors increase their interactions with the real world (water, plants, animals, rocks and sky), but well planned lessons and fun games will increase their understanding of how the natural world works to provide them with what they need to live. The air they breathe, the water they drink, the materials necessary to construct their homes and schools, and the electricity that comes from the outlets are all taken for granted until these processes are understood. Ultimately, if I can help a child to understand how the Earth and the Sun have been working together for billions of years to produce the things necessary for their survival and enjoyment, I feel that I have taken a step toward the even larger goal of encouraging them to be stewards of those resources and processes.
If I can, in addition to this, make the outdoors an exciting and adventurous place to play and learn, then I will have helped to set them on path of appreciating nature for the rest of their lives. Books such as "Last child in the woods" make glaringly obvious the social, psychological and physical benefits of such a lifestyle choice early in life. With a wealth of environments with which to interact, countless questions to be answered, and sensations to stimulate all the senses, the outdoors is a classroom unparalleled by any constructed environment. For the health of future generations, a true, hands-on understanding of how the world works, and a way to connect to the natural world that they are a part of, I choose to spend my time teaching children outdoors.