All ecosystems on Earth are formed of a delicate balance of species. When an ecosystem is at equilibrium, the relative numbers of organisms within each species remain stable. A food web is a graphical representation of the trophic (food-based) interactions between species. Arrows are drawn between every species and its prey, and the sum of these interconnections forms a complicated tangle of lines. In 1966 Robert Paine, an American ecologist, conceived of the idea that not every interaction in the food web is equally important in maintaining the equilibrium of the ecosystem.

Some species can dramatically increase or decrease in population and have little effect on the gradual return of a static-state ecosystem. This means that if this species propagates or dies off in large numbers, the relative population sizes of other species in the community will be skewed, but the community will eventually return to its...