EarthLabs > Corals > Lab 5: Trouble in Paradise: Factors that Impact Coral Health > 5B: Human Activities That Threaten Coral Reefs

Trouble in Paradise: Factors that Impact Coral Health

Part B: Human Activities That Threaten Coral Reefs

The practice of blast fishing is destructive not only to targeted species, but also to reef structure and the entire ecosystem. This image shows damaged coral and fish left as waste after a blast in Indonesia. Image courtesy of NOAA and Berkley White, ©2004.

The Reefs at Risk map layers in ReefGIS allow you to separate the effects different human activities have on coral reefs. By evaluating the contributions various human activities have on the estimated overall threats to Caribbean coral reefs, you will be able to better identify the major causes of reef degradation and understand the links between human activities and reef conditions.

  1. Examine the other Caribbean (2004) map layers to determine the extent to which Caribbean corals are affected by each of the following:
    ReefGIS Threat Layers
    Image provided by ReefBase.
    1. From within the "Layers" tab, click on the white circle next to "Watershed" in the "Reefs" column. Then click the "Refresh Map" button.

    2. Examine the map and take notes to document your observations.

    3. Next, examine the Watershed "Threats" map by clicking on the appropriate white circle and refreshing the map. Again, take notes to document your observations.

    4. Repeat the above steps for the Marine Pollution, Overfishing, and Coastal Development maps.

    Stop and Think

    1: How do the threats posed by watersheds, marine pollution, overfishing, and coastal development compare to one another? Which factor appears to have the largest impact on coral reef health in the Caribbean? Explain.

  2. Read the Coral Reef Alliance articles to find out more about the effects of watersheds, exploitive fishing, and coastal development on coral reefs. Then answer the associated Checking In questions.

    Checking In

    Answer the following questions to check your understanding of what you read.


    • How does watershed pollution harm coral reefs?
    • What are some ways to protect corals from watershed pollution?

    Exploitive Fishing:

    • What are the two main types of exploitive fishing?
    • Name four negative impacts of exploitive fishing.

    Coastal Development:

    • How is coastal development harmful to coral reefs?
    • How does the degradation of coral reefs from coastal development impact a country or region's economy?
    • What is ICZM and how can it help alleviate some of the negative impacts coastal development has on coral reefs?

    Stop and Think

    2: Can you think of any other activities or phenomena that might be harmful to coral reefs? Explain.