4. Coastal Zone Interactions and Threats

How are the different communities in the coastal zone linked?

Land   Mangroves   Sea Beds   Coral Reefs
Prevents erosion Arrow pointing left Trap sediment and detritus (rotting material) Arrow pointing right Trap and stabilizes Sediments (materials) Arrow pointing right Prevent smothering (cover heavily and killing)
Protects towns and villages Arrow pointing left Protect shore from storms Arrow pointing left Protect shore from storms Arrow pointing left Protect land from strong waves
    Provides safe environment for young fish Arrow pointing right Provide safe environment for young fish Arrow pointing right Greater fishing yields (catch)
  Arrow pointing right Stop pollution from the land getting into the sea Arrow pointing right Take up nutrients(food materials) and recycles them Arrow pointing right Clean clear water and normal algae(seaweed) levels
    Provide dead plant material (parts of plants) for food Arrow pointing right Nutrients for seagrass Arrow pointing right Nutrients for communities and inverts (organisms without backbones)
        Provide safe environment for fish at night Arrow pointing right Provide area for schooling fish (fish that go in groups)

Dangers to the Coastal Zone

Threats to the forests:

The biggest threats to forests are human activities, just like mangrove forests and seagrass beds. This includes the removal of forests (deforestation) and bad farming practices. Farming practices that are considered to have harmful effects are: “slash-and-burn” farming (cutting and burning), highland (farming on a hilly area) vs. lowland farming, and also keeping too many farm animals, like goats which eat up all the plants and trees. Good farming practice involves reforestation (planting new plant and trees after cutting them) programs for logging (cutting down trees for logs), lowland farming and the rotation of fields for farming, and also good management for farm animals.

What happens when we do not practice good farming techniques?

  1. The roots of the trees, shrubs, and plants in the forest keep the soil and land stable (the roots hold the soil together). This prevents soil erosion (washing away of soil).
  2. If there is nothing to hold the soil together, masses (big amounts) of soil and other run-off (movement of materials from one area onto another) will easily reach the shore, especially from the rivers and streams or if there is heavy rain. This run-off will drain in to the ocean. Chemicals, fertilizers (used to make the soil rich in food for the plants) and pesticides (for killing pests which harm the plants) may be present in this run-off.
  3. If there is too much livestock in one area, the animals will eat up all the vegetation in that area. Without the vegetation, soil erosion will occur.

Threats to mangroves:

The biggest threat to mangroves is their removal by people. This is usually undertaken so that the land they are on can be developed or built upon, or so fishing boats can reach the shore easily. Once the mangroves are removed, they cannot provide the benefits (good use) to the rest of the environment.

What happens when we remove the mangrove forests?

  1. Pollution (dumping of waste carelessly) and run-offs from the mainland will not be trapped and will not be filtered by the mangrove roots.
  2. Mangroves are home to many marine animals, including fish, jellyfish, mudskippers, seabirds, prawns and baby fish. When these baby fish grow old, they leave the mangroves to live on the reef. Removing the mangrove forest removes their home and protection.
  3. Soil erosion from the seawall (walls built on the seashore) or seashore can occur. This will cause the loss of land from the coastline.

Threats to seagrass beds:

The biggest threat to seagrass beds is the same as mangroves. This is the threat from human beings. The building of houses, hotels, towns, cities, industries, and roads are a danger to seagrass beds. These activities cause a physical change to the seagrass beds.

What happens when we remove the seagrass beds?

  1. Seagrass beds provide shelter for many marine animals, for example, molluscs, fish, sea cucumbers and sea urchins. Removing the seagrass beds removes their shelter.
  2. Seagrass beds provide feeding grounds (a place to eat) for many marine animals. Without these beds, many of these animals would have no safe area to feed.
  3. There will be no plant root system to stabilize the sandy lagoon areas (shallow area of the sea that is sandy and is surrounded by a reef and a beach). Sediments (materials) will be able to reach the reef without being trapped through the seagrasses, which acts as a filter, first. Coastal erosion (movement of the coastline towards the sea or land) along the coast can also occur.

Threats to the reef:

Corals are vulnerable to changes in their environment. These changes can happen naturally. Humans also harm coral reefs—our everyday activities can threaten the reef in a number of ways. Many of the threats that have bad effects on the mangrove forests and seagrass beds will also threaten the health of the coral reefs.


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