Download How Ecosystems Change

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