If you are joining a 2-week expedition or a 1-week project, then yes, you do. We make it compulsory that each team member holds a suitable travel insurance policy, which covers them fully for the activities detailed in the briefing, and provides cover for emergency medical repatriation. You should pay special attention to the fact that your policy covers you for adventurous activities and/or light manual work. See www.biosphere-expeditions.org/affiliates for some insurance companies that we recommend.