Severn is an activist and writer who has been speaking out about social justice and environmental issues since she was small. At age 9, she started the Environmental Children's Organization (ECO) with a group of friends committed to learning and teaching others about environmental issues. In 1992, with ECO, Severn attended the Rio Earth Summit, where, at the age of twelve, she delivered a powerful speech that garnered worldwide attention. For this she received the UN Environment Program's Global 500 Award in Beijing the following year.