Understanding Coastal Erosion and Coral Reef Ecosystems
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Cliffs and Wave-Cut Platforms
- Erosion is greatest when large waves actually break against the foot of a cliff.
- As the notch gets larger, the cliff above will become increasingly unsupported and, in time, will collapse.
- As the process is repeated, the cliff will slowly retreat and usually increase in height.
Caves, Arches, and Stacks
- Where headlands are formed, there is resistant rock, but they are still likely to contain areas of weakness.
- Areas of weakness will be the first to be worn away by the sea.
- First, a cave will form; later, an arch; and at the end, a stack (as the rock above the arch becomes unsupported, it collapses).
Types of Reefs
There are three types of reefs:
- Fringing Reef – Coral platforms grow out to sea attached to the mainland.
- Barrier Reef – Coral grows in a shallower area away from the mainland.
- Atoll – These develop around islands.
Conditions Coral Reefs Need to Grow:
Coral has a solid skeleton of limestone and forms reefs at a rate of 2.5 cm a year. Coral needs three main factors to grow:
- Warm water between 23 and 25 °C is best (tropical zones).
- Plenty of sunlight to aid photosynthesis.
- Clear, shallow saltwater, no deeper than 50 meters, because coral cannot grow in freshwater.
Coral Reefs Under Threat
Coral reefs provide habitats for a marine ecosystem full of color, patterns, and bizarre life forms.
- Some 3,000 species have been recorded on a single reef.
- This provides tourism, which has some positive and negative effects:
- Positive: They create employment and income in some of the world’s poorest regions.
- Negative: They damage coral while swimming beneath the sea.
Already, 25% of reefs have been damaged or lost.
Great Barrier Reef:
- Agriculture: Pollutants used for growing arrive in the sea from the river.
- Tourism: Tourists often stand on or bump into living coral.
- Fishing: Overfishing the reef affects the top layers of the ecosystem.
- Industry: Rivers bring toxic and metal pollutants to the reef from industrial activities.