We have been discussing the powerful and essential ecological link between apex predators, their prey, and the foods prey eat. Based on the revolutionary ideas of Hairston, Smith, and Slobodkin, who in 1960 ingeniously proposed that the world is green because predators limit their plant-eating prey, trophic cascades science has since then explored the consequences of predator removal from ecosystems worldwide.
In all ecosystems, researchers have found a strong link between predator removal, plant community simplification, and reduced energy flow. Lacking apex predators, ecosystems become capable of supporting fewer species, because the trees and shrubs that create habitat for these species have been over-browsed. With top predators in them, they contain richer and more diverse habitat, and thus can support a greater number of species such as songbirds and butterflies. Apex predators are thus thought to exert top-down effects on ecosystems.
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Dr. Cristina Eisenberg is the lead scientist at Earthwatch Institute, a Smithsonian Research Associate, and a Boone and Crockett Club professional member. She is the author of The Wolf's Tooth and The Carnivore Way.