Answer:
Predators eat prey. In doing so, predators can affect both prey abundance and their behavior (for example, prey gets scared when predators are around and hide or move away). In this situation, by controlling the densities and / or behavior of their prey, predators indirectly benefit and increase the abundance of their prey. Trophic cascades by definition must change at a minimum of three feeding levels. In fact, this is how it occurs most frequently (predator => herbivore => primary consumer), although evidence of trophic cascades of 4 and 5 levels has been detected in nature, but they are much less commo
When ecosystems are green, predators are often frequent with herbivores under control, while, when they are too overloaded, the loss or elimination of predators is often responsible for high grazing densities and loss of plants. This tri-trophic interaction, where predators benefit from plants by controlling herbivore populations, is known as the trophic cascade. Hairston et al. (1960) proposed for the first time that the world is green because predators control herbivores, and Carpenter and his colleagues further developed the concept of trophic cascade with experimental studies in lakes, demonstrating that fish can control the abundance of zooplankton which, in turn, controls phytoplankton levels
