Trophic Cascades
Trophic cascade: effect of one trophic level flow up or down to more than one adjacent trophic levelExample: a predator (lion) not only affects its prey population (impala) but, by its grazing on the prey, also the prey’s prey (grass)
Top-Down effects: predators control lower trophic level populationsExample: in the presence of herbivores, why is not all plant life consumed? Predators keep herbivore population to a level that the herbivores cannot extinct the plants
Bottom-up effects: resources or lower trophic levels control upper trophic level populationsExample: low nutrient concentrations constrain plant production, which will constrain herbivore production, which will constrain carnivore production
Humans can affect trophic cascades by removing top predators(e.g. removal of wolves ? increase in deer ? forest destruction)