2.5 Natural Disruptions to Ecosystems

Disturbances shape ecosystems

Natural disturbances are events that disrupt ecosystems, changing resource availability and community structure. Examples include wildfires, volcanic eruptions, floods, hurricanes, droughts, and disease outbreaks. These events can be periodic or unpredictable, and ecosystems often show resilience by recovering over time through succession.

Succession after disturbance

Primary succession occurs on lifeless substrate (e.g., after a volcanic eruption or glacial retreat), starting with pioneer species like lichens. Secondary succession occurs where soil remains after disturbance (e.g., after a wildfire or hurricane), so recovery is faster. Both processes gradually rebuild biodiversity and complexity toward a more stable community.

Ecosystem resilience and change

Resilience is an ecosystem's ability to recover after disturbance, while inertia (resistance) reflects its ability to resist change altogether. Some disturbances, like periodic wildfires, are actually necessary for ecosystem health, releasing nutrients and clearing dead material. Severe or frequent disturbances, however, may push an ecosystem past a tipping point into a new state.

Key terms

Natural disturbance

An event like a wildfire, flood, hurricane, or volcanic eruption that disrupts an ecosystem's structure and resources.

Primary succession

Ecological development on bare substrate with no existing soil, beginning with pioneer species.

Secondary succession

Ecological recovery in an area where soil remains after disturbance, allowing faster regrowth than primary succession.

Resilience

An ecosystem's ability to recover and return to its original state after a disturbance.

Inertia (ecological)

An ecosystem's ability to resist change or disturbance in the first place.

Try an AP-style question

A hurricane destroys coastal habitat. How is this disruption best classified?

1. Constant
2. Episodic
3. Artificial
4. Periodic