8.7 Disruptions to Ecosystems

Natural and human disruptions

Ecosystems can be disrupted by natural events (fires, floods, storms) and by human activity (pollution, habitat destruction, overharvesting, climate change). A disruption at one trophic level can ripple through the whole community — a trophic cascade.

Invasive species and recovery

An invasive species is a non-native organism that spreads and harms an ecosystem, often outcompeting natives. After a disturbance, an ecosystem can gradually recover through ecological succession — the orderly, step-by-step return of a community. Losing a keystone species can cause large, cascading changes.

Key terms

Ecosystem disruption

Natural (fire, flood) or human (pollution, climate change) events that alter an ecosystem.

Invasive species

A non-native species that spreads and harms an ecosystem, often outcompeting natives.

Trophic cascade

A disruption at one trophic level that ripples through the food web.

Ecological succession

The gradual, step-by-step recovery of a community after a disturbance.

Human impact / climate change

Habitat loss, pollution, and greenhouse gases from humans disrupt ecosystems worldwide.

Try an AP-style question

An invasive species often spreads rapidly in a new environment. What is the most likely reason?

1. It always has a higher mutation rate than native species
2. It cannot reproduce in its native habitat
3. Native species help it spread on purpose
4. It has no natural predators, parasites, or competitors there