Internships in the environmental sector provide great training ground for students to explore the broad terrain of this field, from conservation, climate change, and sustainable development, to policy, advocacy, and government. Students usually determine whether interests lie on the scientific underpinnings of environmental issues (i.e. the science behind climate change), or the policy implications of environmental issues (i.e. legislation and advocacy seeking to avert climate change) before choosing an appropriate experience. The internship sites below provide examples of the types of experiences Harvard students typically pursue.
From OCS Presentation: Finding Internships in Energy, Environment, and Sustainability (pdf)