Changes in Ecosystems

Succession is the gradual development of an ecological community or its replacement by another.

Ecosystems may change gradually, as months and years

pass, or quite suddenly if a storm hits or a volcano erupts.

Natural eutrophication is one example of a gradual change that transforms a body of water, such as a lake or a pond, into a meadow.

It occurs when a body of water receives enough nutrients to support large amounts of plant or algal growth.

Human actions sometimes result in artificial eutrophication, such as when fertilizer washes into a lake from farms or lawns.

Sudden changes to ecosystems can occur due to natural events, such as severe storms, fires, and volcanic eruptions.

The eruption of Mount St. Helens buried the surrounding area in ash and debris, yet the ecosystem recovered quickly.

Fires also clear out understory vegetation that blocks light and adds nitrogen rich ash to the soil.

Pioneer species, which are the first organisms to arrive, help break down rock and form soil. 

Producers, such as lichens, are the first pioneer species to arrive.

After the pioneer species come

a succession of plants, including

mosses, ferns, grasses and herbs.

Secondary succession occurs where soil still exists.

Examples include the succession that occurs after a natural disturbance or disaster, or even on an abandoned farm.

Secondary succession occurs much faster than primary succession.

Over time, succession creates a climax community.

A climax community does not last forever. It will be replaced by a community of different species following another natural disturbance.