We all know that whales are endangered due to hunting and pollution, but do you know how important they are for the ocean and the environment? This video shows how essential a healthy population of whales is to the ocean ecosystem. Creative Commons Attribution license (reuse allowed). Video was not modified. Please visit sustainablehuman.org for credits and more information.

When wolves were reintroduced to Yellowstone National Park in the United States after being absent nearly 70 years, the most remarkable "trophic cascade" occurred. What is a trophic cascade and how exactly do wolves change rivers? George Monbiot explains the process.

The story told in this animation reminds us that we can never predict the exact outcome of things that happen in our lives. Please visit sustainablehuman.org for credits and more information.