5.1: Natural Phenomena and

EcosystemsCh: 5 Changing the Balance in Ecosystems

Typhoon Haiyan homeless

Recall from Ch: 2 that natural ecosystems maintain a dynamic equilibrium. Biotic and abiotic factors change over time.

Natural events are part of our biosphere’s dynamic quality Eg: Volcanic eruptions, earthquakes,

tsunamis have both negative and positive

consequences.

What happens after a natural phenomena?

Healthy ecosystems will respond by adapting. The time taken to adapt may vary.

Natural succession may create a similar ecosystem as was previous, but not necessarily.

Case Study #1: Mount St. Helens

Erupted May 18th, 1980

Wiped out the surrounding ecosystem.

Debris flow filled river valleys killing aquatic organisms.

Hot ash burned hundreds of old-growth forest.

http://www.youtube.com/watch?v=-H_HZVY1tT4

A. Weather related phenomena

Eg: Floods, droughts, tornados, hurricanes, blizzards, infestations.

The warming of atmospheric air and ocean temperature are contributing to the severity of weather related phenomenon.

Case Study #2: Pine Beetle

Pine Beetle has infected acres of trees across British Columbia.

Live inside the bark and digest sapwood.

Beetle cuts off trees nutrients and obstructs water movement.

How does weather play a role?

In previous years the pine beetle population has been kept in check as many larvae were killed off during cold, winter months.

Now BC climate has become milder.

http://www.youtube.com/watch?v=yo69NtUMXBY

B. Geological events Some natural phenomena are the result

of geological activity in Earth’s crust.Examples: Volcanic eruptions,

tsunami

Volcanic EruptionNegative

Habitat destruction Vegetation covered

by ash Landslide Ash in atmosphere

Positive New lakes New soils