5.1: Natural Phenomena and Ecosystems Ch: 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 18 th, 1980  Wiped out the surrounding ecosystem.  Debris flow filled river valleys killing aquatic organisms.  Hot ash burned hundreds of old-growth forest.

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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.

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B. Geological events  Some natural phenomena are the result of geological activity in Earth’s crust. Examples: Volcanic eruptions, tsunami

Volcanic Eruption Negative  Habitat destruction  Vegetation covered by ash  Landslide  Ash in atmosphere Positive  New lakes  New soils