Cacading Trophic Effects

Cascading Trophic Effects in Response to Apex Predator Removal
Introduction
The seemingly simple interaction between predator and prey can create effects that disseminate throughout an entire ecosystem. These interactions, or lack thereof, specifically result in trophic cascades. Cascading trophic effects typically occur from a change in the population density of apex predators. Due to the ever increasing impact of humans on nature, this field of ecological study is gaining more popularity as ecologists desperately try to understand the various influences of apex predators on ecosystem functioning. Numerous studies have displayed diverse effects that apex predators can inflict upon other animal and plant species, in both terrestrial and aquatic
This definition represents the simplest and most studied cascade, which is referred to as being tri-trophic. Due to nature’s complexity and the millions of extant species of plants and animals, cascading trophic effects are capable of running through multiple trophic levels. Depending on the species, or location, effects from apex predators can cascade through four, seven or twenty trophic levels. The occurrences of trophic cascades have been recognized in all of Earth’s major
The cascading effects that follow the removal of an apex predator result in a secondary predator gaining primary control, and often have negative impacts on the ecosystem, hence the term ‘downgrading’. The changes accompanying an ecosystem’s loss of apex predators are often times rapid, and can be difficult to reverse. Although the ecosystem may react swiftly to a loss of apex predators, the long generation times of some species may delay visible ecosystem responses for years or decades (Estes, 2011). Unfortunately, when responses are eventually recognized, it is often too late to reverse the damage. From the definition of trophic cascades, it is clear that the general system of herbivore control is predation; therefore, an absence of apex predators may allow herbivores to expand to the point of vegetation depletion (Hairston, 1960). Furthermore, a substantial decline of apex predators can result in a shift from top-down to bottom-up driven ecosystems, thus allowing some species (herbivores) to achieve high abundances at a cost to other species (autotrophs) (Wallach, 2015). Globally, there have been wide-ranging effects of losing apex predators, most of which have resulted in species homogeneity and the simplification of food-webs (Bestion, 2015; Broderson, 2015; Estes,