When is a trophic cascade a trophic cascade?

Trophic cascades are the time-honored focal point of food-web dynamics. They are the best loved example of indirect effects in undergraduate ecology textbooks and they represent a potentially useful application of theory. Researchers have found them from the Arctic to the tropics. But, can we agree on what they are? Here, we seek to clarify the terminology of trophic cascades and call for a consensus on how to quantify cascading effects in the future.