Question 6: What are the different factors that influence the Green World Hypothesis? By: Mele Moniz Nicole Huffman

Green World Hypothesis States that terrestrial herbivores consume relatively little plant biomass because they are held in check by a variety of factors, including predators, parasites, and disease. This theory is credited with bringing attention to the role of top-down forces and indirect effects in shaping ecological communities.

Plants Plants have defenses against herbivores such as noxious chemicals and spines. Nutrients, not energy supply, usually limit herbivores. Plants give off a low supply of protein, which animals need.

Abiotic Factors Changes in temperature and moisture will lower the carrying capacity of herbivores so that they're unable to strip an area of its vegetation.

Intraspecific Competition Limits herbivore numbers because they may battle over territory or mates.

Interspecific Interactions Such as predation and disease will kill herbivore densities in check. This is said to be the most important limiting factor. - Predators in a food web suppress the abundance of their prey, thereby releasing the next lower trophic level from predation.

On a Related Note…Trophic cascade Nelson Hairston, Frederick E. Smith, and Lawrence B. Slobodkin are credited with the concept of trophic cascade, despite never using the term. They argued that predators reduced the number of herbivores and therefore allowed plants to flourish, a.k.a. the green world hypothesis. Previously, trophodynamics was used to explain the structure of communities using the bottom-up forces, or resource limitation. Hairston, Smith, and Slobodkin argued that ecological communities acted as food chains with three trophic levels. Other models have expanded and shrunk this model. Hairston, Smith and Slobodkin formulated their argument in terms of terrestrial food chains, the earliest empirical demonstrations of trophic cascades came from marine and, especially, aquatic ecosystems.