We developed a two-day physics class that uses a nearby forest as a teaching location. Using low-cost material, students design and carry out physics projects outside of the usual controlled environment that is a classroom. In this way, they come to realize that physics can be used to understand the real world. They organize and present their results in an original format, an exhibit they collectively build. This project is an introduction to the role physics can play in exploring environmental issues, incorporating a sensitive and positive aspect which is important in this time of environmental crisis.