Criticism
One of the main criticisms of the mesopredator release hypothesis is that it argues in favor of the top-down control concept and excludes the possible impacts that bottom-up control could have on higher trophic levels. This means that it supports the argument that top predators control the structure and population dynamics of an ecosystem, but it does not take into account that prey species and primary producers also have an effect on the ecosystem’s structure. Another major problem is that the hypothesis is offered as an explanation after large predators have already become rare or extinct in an ecosystem. Consequently, there is no data on the past ecosystem structure and the hypothesis cannot be tested. As a result, information on the past conditions has been inferred from studies of the present conditions. However, contemporary examples of mesopredator release exist, such as the culling of cats on Macquarie Island.
The hypothesis is sometimes also applied to humans as apex predators that produce top-down effects on lower trophic levels. However, it fails to recognize bottom-up effects that anthropogenic land transformations can have on landscapes on which primary producers, prey species, and mesopredators dwell. Possible bottom-up effects on an ecosystem can be from bioclimatic impacts on ecosystem productivity and from anthropogenic habitat alterations. Examples of anthropogenic habitat change include agriculture, grazing land, and urbanization. More importantly, the hypothesis does not take into account that higher trophic levels are affected by primary productivity. It also does not mention that trophic interactions operate at different strengths according to the ecosystem. Therefore, the roles of predation and food/nutrient processes in influencing ecosystem structures remain open to controversy and further testing.
Read more about this topic: Mesopredator Release Hypothesis
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