2.5: Natural Disruptions to Ecosystems

Change is a Constant

Our Earth, due to species interference and the life cycles, experiences constant changes. Some are slow and always evolving, some are fast and sporadic, and some are somewhere in the middle. Effects that these processes have can be drastic or negligible to certain ecosystems, and can happen to have short-term or longer-term effects. Manmade, or anthropogenic, disasters may be equal to any natural counterparts. 

These alterations in Earth's happenings can be random (like a lightning strike from one storm), seasonal (the months in which hurricanes occur to form a hurricane season), or by episode (like stages of a volcanic eruption). For example, glaciers and climate change are contributing to sea level rise, which increases flooding in coastal cities or communities. These are manmade disasters that can have great effects on ecosystems. Naturally, disasters such as the cold can cause migrations, such as geese in Canada finding similar conditions further south to escape snow and ice storms during winter.

Resistance and Resilience

Resistance is a measurement of how much an ecosystem changes after a disruption (forest fire, invasive species...).  If there is little change, the ecosystem has a high resistance and is considered to be quite stable. That is to say, this ecosystem would bear the brunt of the disaster without experiencing much internal damage.

Resilience is the measure of how quickly the ecosystem can ‘bounce back’ from the disturbance. It is a measure of how quickly an ecosystem can recover and rebuild its environment.

Intermediate Disturbance Hypothesis

Maximum species diversity is reached when an ecosystem experiences an intermediate level of disturbance. It is because both early and late succession species are able to survive at the same time. An early succession species (grasses, shrubs) is one that is able to exist in an ecosystem first, requiring fewer nutrients and existing with less interspecies competition. A late succession species is the opposite, and has found the ecosystem more recently. So, an ecosystem with a moderate amount of disturbance (detectable, not destructive!) will allow all succession levels to survive the best they can