“If a Tree Falls” depicts the rise and fall of the Earth Liberation front through the transformation and radicalization of one of its members. Part coming-of-age tale, part cops-and-robbers thriller, the film interweaves a chronicle of Daniel McGowan on house arrest as he faces life in prison, with a dramatic recounting of the events that led to his involvement with the group, and asks hard questions about environmentalism, activism, and the way we define terrorism.