A Trophic Cascade

A trophic cascade can be defined as "An ecological phenomenon triggered by the addition or removal of top predators  and involving reciprocal changes in the relative populations of predator and prey through a food-chain, which often results in dramatic changes in ecosystem structure and nutrient cycling." - Encyclopedia Briticanna 

Here Sustainable Human explores to Trophic Cascade that occurred after wolves were re-introduced back into Yellowstone National Park.

They also explore the impact of Whales on the oceans.