Wessels earned a BS in wildlife biology from the University of New Hampshire and a MA in ecology at the University of Colorado. Wessels went directly into academia, beginning with a post at the now defunct Windham College, in Putney, Vermont. In 1978 he became an adjunct faculty member at Antioch University New England and was instrumental in developing numerous courses in the yet very young Environmental Studies Department. He became a core faculty member at Antioch in 2000.

In addition to teaching at Antioch, Wessels has traveled on expedition to Iceland with Haraldur Sigurdsson. He chaired the Science department for ten years at The Putney School, a boarding high school in Putney, Vermont. He served as the chair of the Robert and Patricia Switzer Foundation, a foundation that provides grants and fellowship to promote environmental leadership. Since 1995 he has served as an ecological consultant for the Rainforest Alliance SmartWood Program in the Northeastern United States.