28.12: Ecological Disturbance
An ecological disturbance is a temporary disruption in the environment resulting from abiotic, biotic, or anthropogenic factors, causing a pronounced change in an ecosystem. The impact of an ecological disturbance, which can depend on its intensity, frequency, and spatial distribution, plays a significant role in shaping the species diversity within the ecosystem.
Ecological disturbances can be caused by an event as small as the trampling of underbrush to an incident as wide-ranging as a forest fire or flood. Natural events like volcanoes and hurricanes, biological interferences like grazing and pest outbreaks, and human activities like deforestation can contribute to generating ecological disturbances.
Key biological processes like mortality, reproduction, movement, and social behavior within the populations in an ecosystem can be affected by disturbances. Severe disturbances resulting in high mortality can reduce population size, leading to a loss in genetic diversity, if the recovery time of the population and immigration rates are following the incident. Disturbances also affect genetic differentiation within a population by influencing genetic drift and migration.
Ecological disturbances cause variations in the strength and direction of natural selection, leading to unpredictable evolution patterns. The selection process following a disturbance can thus alter the phylogenetic composition of communities.
Intermediate disturbance hypothesis states that ecological disturbance results in maximum species diversity when the disturbance is neither too rare nor too frequent. Highest diversity occurs at levels of moderate disturbances, characterized by intermediate levels of intensity and frequency.