What can trigger a trophic cascade?

A trophic cascade is an ecological phenomenon that occurs when changes at the top of the food chain influence multiple lower trophic levels. The removal or addition of top predators is a significant trigger for such cascades because top predators regulate the populations of their prey, which in turn affects other species in the ecosystem.

When a top predator is removed, the population of primary consumers (herbivores) often increases unchecked, leading to overgrazing or overbrowsing of primary producers (plants). This can result in a decline in plant diversity and biomass, destabilizing the ecosystem. Conversely, the introduction of top predators can control herbivore populations, allowing for the recovery of primary producers and leading to increased biodiversity overall.

In contrast, while the loss of primary producers, the introduction of herbivores, and the growth of primary consumer populations can also lead to changes in an ecosystem, these factors do not initiate a trophic cascade as directly or significantly as the alteration of top predators does. The key impact of the predator dynamics resonates throughout the food web, making the removal or addition of top predators a fundamental trigger for a trophic cascade.