1. How Ecosystems Change Ecosystems are constantly changing.
Ecological succession is the gradual process of change and replacement of some or all of the species in a community.
Succession can take decades or thousands of years.

2. Another example of secondary succession
How Ecosystems Change
Another example of secondary succession

3. How Ecosystems Change

4. How Ecosystems Change
Primary succession is the type of succession that occurs on a surface where no ecosystem existed before, such as on rocks on sand dunes. It is very slow because there is no soil. It can take several hundred to several thousand years to produce fertile soil. Lichens are usually the first organisms to colonize bare rock. They break down the rock which eventually turns into soil.
Primary succession on Rangitoto island

6. How Ecosystems Change
Secondary succession, the more common type of succession, occurs on a surface where an ecosystem has previously existed.
Secondary succession occurs in ecosystems that have been disturbed or disrupted by humans or animals, or by natural processes such as storms, floods, earthquakes, and volcanoes.
Secondary succession near Mt. St. Helens

7. Now secondary succession is occurring and plants are coming back.
How Ecosystems Change
When Mount St. Helens erupted in 1980 it decimated almost 45,000 acres of forest and vegetation.
Now secondary succession is occurring and plants are coming back.