Explain what the "Green world hypothesis" is. *

First propounded in 1960 by United States scientists Nelson Hairston, Frederick Smith and Lawrence Slobodkin, the hypothesis states that predators more than plant defences are responsible for limiting herbivore spread which would, in turn, lead to large scale destruction of plant life.

While this is difficult to test in the wild because of the impossibility of removing all predators from a test site, this was proved at a Venezuelan hydroelectric project site where the flooding caused by the dam resulted in several islands being formed. On those where predators were absent, a larger destruction of green cover was detected than on those islands or mainland patches where herbivores and predators co-existed.