The fragility of ecosystems: a review.
Abstract
The identification of species, communities, or ecosystems that are likely to be strongly damaged by human activities (i.e. that are fragile) forms an essential part of nature conservation management. The meaning of ecosystem fragility, which is defined as the inverse of ecosystem stability, is reviewed. Fragility may be regarded as an inherent property of an ecosystem, i.e. an ecosystem has a certain fragility whether or not it is ever exposed to any disturbances. This fragility is impossible to quantify, leaving it as a mere metaphysical term. The only observable fragility is that displayed as a result of disturbances, natural as well as human-caused, operating in the ecosystem. Therefore, relating ecosystems to the disturbances that work there can provide useful assessments, an approach closely related to environmental impact assessment. Basically, fragility and stability of an ecosystem relate to degree of change in species abundance and composition, following disturbance. High rates of species turnover or population fluctuations characterize fragile ecosystems, and vice versa. The diversity of ecological processes related to these changes makes ecosystem fragility a central evaluation criterion in conservation management. Fragility is also closely related to many frequently used criteria in evaluation and assessment for conservation. Application of the concept of ecosystem fragility in nature conservation, how to systematize its assessment, and how to locate especially fragile areas, are discussed.