Hydroelectric schemes usually generate a barrage of criticism from conservationists. But the flooding of a Venezuelan valley 20 years ago has provided ecologists with the ideal outdoor laboratory to answer one of ecologys oldest and thorniest questions: why is the world green?
Reporting their results in the March issue of the British Ecological Societys Journal of Ecology, a team lead by Professor John Terborgh of Duke University says that the role of predators is the key to keeping the world green, because they keep the numbers of plant-eating herbivores under control. Their results support the so-called “green world hypothesis” first proposed in 1960 by Hairston, Smith and Slobodkin and seem to lay to rest the competing theory that plants protect themselves from being eaten through the physical and chemical defences they have developed.
Despite being nearly 50 years old, the green world hypothesis has been almost impossible to test until now. According to Terborgh: “Since the landmark paper by Hairston et al, ecologists have been debating whether herbivores are limited by plant defences or by predators. The matter is trivially simple in principle, but in practice the challenge of experimentally creating predator-free environments in which herbivores can increase without constraint has proven almost insurmountable.”
Becky Allen | alfa
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