Disequilibrium Essay ⋆ Environment Essay Examples ⋆ EssayEmpire

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Disequilibrium , as used in ecology, is a term used to describe systems that do not tend toward a stable, homeostatic balance. Whereas an ecological system in equilibrium tends toward stability both in terms of species composition and cycling of abiotic nutrients and energy, a system in disequilibrium exhibits no stable end point, has species composition in flux, and exchanges nutrients, energy, and organisms with surrounding systems.

Disequilibrium systems can be either dynamic or static. With dynamic disequilibrium, disturbances to environments occur too frequently for a stable equilibrium to be reached, and species turnover, the rate at which become locally extinct from a given location and are replaced by new species, is driven by the interaction between frequency of disturbances relative to the mortality and reproductive rates of constituent species. Disequilibrium in ecology thus relies on autecological explanations by examining the response of individual species to various environmental stimuli. In contrast, equilibrium approaches focus on the formation of stable assemblages, and tends to be concerned about the responses of entire communities to environmental stimuli (synecology).

Static disequilibrium occurs when species composition in a given area remains stable over short to medium time-scales (hence it is static), but changes when viewed over long time-scales. Disturbance is more prominently featured within disequilibrium ecologies as well. Within equilibrium ecology, disturbance is a viewed as an aberration that interrupts the natural development of stable ecosystems. Disequilibrium ecology views disturbance as a vital and natural component of proper ecosystem functioning, depending on the frequency and spatial scale of disturbances.

Disequilibrium Approach

The intermediate disturbance hypothesis is an example of a disequilibrium approach to ecology. Following disturbance, rapidly reproducing and dispersing pioneer species (r-species) with short life spans tend to dominate the area of disturbance, and then gradually give way to slower growing, long-lived species characteristic of later successional stages (k-species). The intermediate disturbance hypothesis states that where disturbance is too frequent, species composition becomes skewed toward the pioneer species; whereas if disturbance becomes too infrequent, species composition becomes skewed toward late-successional species. This hypothesis states that the greatest biodiversity occurs with intermediate rates of disturbance, such that viable populations of both r-species and k-species will be maintained. This contrasts with equilibrium approaches, which assert that greatest biodiversity occurs strictly within the stable assemblage of species that develop when disturbance is minimized.

The subject of disequilibrium, especially in contrast to equilibrium, is critical to the philosophy and practice of conservation. Equilibrium approaches to ecology have played a crucial role in the establishment of nature reserves, with a generalized strategy of setting aside large portions of habitat and minimizing disturbance and human involvement. Disequilibrium approaches have been regarded with some suspicion by some conservationists, out of concern that an allowance for disturbance within nature would be used to justify extractive activities and further loss of habitat, despite growing acceptance of disequilibrium ecology’s explanatory power. Other ecologists point out that equilibrium approaches can be detrimental to conservation, in that the Balance of Nature ontology suggests that nature will maintain itself, and obscures the necessary role that people must play in actively maintaining biodiversity, especially in the context of global climate change.

Disequilibrium ecology intersects concerns over environmental conservation and social justice as well. Conservation areas designed under equilibrium perspectives emphasize the importance of increased area to promote higher biodiversity, and tend to grow in size as buffers and connective corridors are acquired. With this expansion, land use conflicts often arise. Additionally, the establishment and maintenance of parks in the developing countries often conflicted with the presence of human populations, often indigenous groups or migrants.

Minimizing Disturbance

Equilibrium design advocates minimization of disturbance and the exclusion of people from conservation areas, and have resulted in local groups being removed from the landscape. Disequilibrium approaches accept some level of disturbance as being necessary and natural to the maintenance of biodiversity and proper functioning of ecosystems. Some level of human use of landscapes can therefore be tolerated by environments, such as fuel gathering or the collection of nontimber forest products. Some reserves in the developing world have been designed to include people living within the its boundaries. The term conservation with development is applied to this application of disequilibrium ecology, allowing a balance of human use with biodiversity conservation.

Bibliography:

Glen M. MacDonald, Biogeography: Space, Time and Life (John Wiley & Sons, 2003);
Michael Soule and Gary Lease, eds., Reinventing Nature? Responses to Postmodern Deconstruction ( Island Press, 1995);
Robert J. Whittaker, Island Biogeography: Ecology, Evolution, and Conservation (Oxford University Press, 1998);
Karl Zimmerer, “The Reworking of Conservation Geographies,” Annals of the Association of American Geographers (v. 90, 2000);
Karl S. Zimmerer and Kenneth Young, eds., Nature’s Geography: New Lessons for Conservation in Developing Countries (The University of Wisconsin Press, 1998).