Human Threats to Coral Reefs

The earth is experiencing Global Warming with higher Ocean temperatures and brought serious problems in the last few decades that seemed unfixable like stressed Coral in the Great Barrier Reef. What are the Human threats to Coral Reefs?

  • Higher H2O Temp. from Global Warming leads to Coral bleaching
  • Higher CO2 gas is absorbed by Ocean causing Acidification.
  • Coastal development
  • H2O activity close to the Reefs
  • Unsustainable fishing creates a lack of food sources
  • invasive species in Reefs
  • Industrial Pollution
  • Stress from recreational damage

For the last 20 years, mass bleaching has been affecting the Great Barrier Reef among others throughout the world. Just when things looked bleak, news of solutions came onto the Horizon.


Where is Coral Bleaching Happening


Warmer water temperatures can result in coral bleaching. When water is too warm, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white. This is called Coral Bleaching. When a coral bleaches, it is not dead.

Corals can survive a bleaching event, but they are under more stress and that takes long periods of time to recover affecting the rest of the ecosystem and could sometime lead to death.

In 2005, the U.S. lost half of its Coral Reefs in the Caribbean in one year due to a massive bleaching event. The warm waters centered around the northern Antilles near the Virgin Islands and Puerto Rico expanded southward.

A comparison of satellite data from the previous 20 years confirmed that thermal stress from the 2005 event was greater than the previous 20 years combined. Not all bleaching events are due to warm water.

In January 2010, cold water temperatures in the Florida Keys caused a coral bleaching event that resulted in some coral death. Water temperatures dropped 12.06 degrees Fahrenheit lower than the typical temperatures observed at this time of year. Researchers will evaluate if this cold-stress event will make corals more susceptible to disease in the same way that warmer waters impact corals.

 Without the zooxanthellae to support their metabolic processes, corals begin to starve. Should the water temperatures return to normal coral can survive the bleaching event. Where bleaching is not too severe, the zooxanthellae can repopulate from the small numbers remaining in the coral’s tissue, returning the coral to normal color over a period of weeks to months.

Some Coral types like the branching type of Coral can only survive for 10 days or without zooxanthellae.  Other massive-size ones can last for weeks at a time.  Even Corals that survive are likely to experience reduced growth rates, decreased reproductive capacity, and increased susceptibility to diseases.

Corals can also acquire a greater tolerance to bleaching stresses if they are constantly exposed to higher temperatures or greater irradiance. Corals on reef flats, for example, will often be able to tolerate much higher water temperatures than colonies of the same species inhabiting reef slopes.

The tradeoff is they grow more slowly. So there is hope for the future that Corals will eventually be able to grow despite ocean water fluctuating temperatures that are caused by warmer ocean temperatures in the future.



Why Are Coral Reefs So Important


At least 500 million people rely on Coral Reefs for food, around the world for coastal protection, and livelihoods. Coral Bleaching not only has a negative impact on the coral itself but the fish that thrive there and on human communities that depend on them to function for livelihoods and well-being. 

Bleached Reefs don’t grow and are susceptible to disease. There is a chain reaction to the problem. Fish that depend on coral communities to live in or feed on lose their home.

Degraded Reefs lose their production of certain species of fish that the coastline community might depend on and the security it provides to shorelines. A healthy ecosystem of coral can provide other products like valuable sources of pharmaceutical compounds used in medicines. Scientist says that millions of people have had their life altered by the loss of a healthy Coral environment.

  • Coral Reefs are a Food Source. At least 500 million people rely on coral reefs for food, coastal protection, and livelihoods. In developing countries, coral reefs contribute about one-quarter of the total fish catch, providing food to an estimated one billion people in Asia alone.
  • Coral reefs form natural barriers that protect shorelines. Protecting from the eroding forces of the sea, thereby protecting coastal dwellings and beaches. More than 150,000 km of shoreline in 100 countries and territories receive some protection from reefs.
  • Coral reefs are the medicine chests of the 21st century. With more than half of all new cancer drug research focusing on marine organisms.
  • Coral reefs have been used in the treatment of cancer, HIV, cardiovascular diseases, ulcers, and other ailments.

In the past few decades, Coral reefs have been threatened worldwide jeopardizing their survival and almost degrading them completely. Most people don’t understand the importance that Coral Reefs have on the coastline around the world.


Their existence plays a key role in human and fish interaction for thousands of years. They are a massive wealth of structure and source for our Earth nurturing and protecting fish and organisms that call it home.

  • Coral reefs are among the oldest ecosystems on Earth.
  • Coral reefs support a phenomenal diversity of species and provide irreplaceable sources of food and shelter to many fish species, including juvenile fish. Tropical rainforests play a similar role on land.
  • Coral reefs exceed rainforests in their diversity.
  • Although coral reefs cover less than 1% of the Earth’s surface, they are home to 25% of all marine fish species
  • Coral reefs support approximately 4000 species of fish and 800 types of corals.
  • Corals are an integral part of the reef; they are the foundational species that provide reef structure.
  • Corals are especially vulnerable to human activities and to climate-related threats.
  • Corals have shown remarkable resilience through major climate events and sea-level changes, giving hope for their continued survival.
  • Most coral reef-dependent countries and territories are small island states, located mainly in the Pacific and the Caribbean.


Human impact on the Great Barrier Reef


Almost 95% of Great Barrier Reefs are currently threatened worldwide, especially in Southeast Asia. Indonesia has the largest area of threatened reefs. More than 75% of the Coral Reefs in The Atlantic are Threatened. Over 65% of the coral reefs in the Indian Ocean and the Middle East are under stress by local threats. In the Pacific Ocean, it’s at 50%.

Besides warming temperatures that create Mass Coral Bleaching, there are other man-made contributors to the problems that affect Coral Reefs Like:

Ocean Acidification The concentrations of CO2 have increased dramatically in the last 100 years through changing in-land mass and burning fossil fuels. The ocean plays an important role in absorbing a huge part of that gas that normally would be let go into the atmosphere. This comes with some cost of creating the problem of Ocean Acidification.

Unsustainable fishing has been identified as the most pervasive of all local threats to coral reefs. Over 55% of the world’s reefs are threatened by overfishing and/or destructive fishing. Some regions, such as Southeast Asia, are particularly threatened, where nearly 95% of reefs are affected. In fact, many of the world’s most remote coral reefs are heavily fished.

Pollution from human activities occurring far inland can have serious impacts on coral reefs. Deforestation and clearing of farmlands result in sediment erosion that flows into rivers and eventually coastal waters. The application of excessive amounts of fertilizer and pesticides spread on crops can wash off or leach out of soils into waterways and coastal ecosystems. It all ends up in the ocean.

Coastal Development-More than 2.5 billion people (40% of the world’s population) lives within 100 km of the coast, adding increased pressure to coastal ecosystems. Coastal development linked to human settlements, industry, aquaculture, and infrastructure can cause severe impacts on nearshore ecosystems, particularly coral reefs. Coastal development impacts may be direct as in landfilling, dredging, coral, and sand mining for construction, or indirect like the increased runoff of sediment and pollutants.

Tourism and Recreational Impacts Recreational activities can harm coral reefs through the Breakage of coral colonies and tissue damage from direct contact such as walking, touching, kicking, standing, or gear contact. Breakage or overturning of coral colonies and tissue damage from boat anchors. Changes in marine life behavior from feeding or harassment by humans Water pollution. Invasive species,
trash and debris deposited in the marine environment all add up and have a negative effect.

Invasive Species-Marine ecosystems contain many species of plants, animals, and microorganisms that have evolved in isolation, separated by natural barriers. Human transportation activities such as shipping and air travel have allowed these species to move beyond their natural ranges into new areas Marine invasive species include:

  • Algae
  • Invertebrates
  • Fishes


These species end up in the Coral Reef and disrupt millions of years of the earth’s evolution that brought this place a natural existence.

Coral Reef Restoration Methods


There is a trial underway to try and restore the damaged Coral on the Great Barrier Reef using electricity. A Conservation Group from Australia call Reef Ecologic led by Research Scientist  Nathan Cook and his team is attempting to regrow coral fragments using electricity on steel frames.

The frames are placed on damaged parts of the reef and stimulated with electricity to accelerate the coral’s growth.

Electrified metal frames have previously been used to encourage coral growth on reefs in South-East Asia, the Caribbean, and the Indian Ocean.

They have been shown to attract mineral deposits that help corals grow 3 to 4 times faster than normal.

Some Coral is growing back but it will take time. It will take a decade for the fastest type of coral to recover and see the fruits of the experiment. Cook and his research team hope that Electric frames will help speed up coral growth so that in the future the technique will help survive future Bleaching events brought on by Global Warming and Rising Temperatures which will go on for years to come.


The Procedure For Growing Coral

Divers attach small chunks of living coral to the wires on the steel frames. Then after that, a steel cable is clipped on from up above the water level that is attached to a raft and power source. Soon tiny Hydrogen bubbles start to rise from the steel frame. The raft has a power source of solar cells. It triggers a chemical reaction with seawater that coats the steel with a form of limestone that corals can’t resist.

Eventually, this metal structure will disappear beneath a multicolored forest of new Coral. A bed of new Coral which is the start of the process fixes itself and creates the Reef. Global Warming creates unimaginable problems that we will face in the future. Some see and some unseen with some coming to a solution and with others only the hope that someday we find one.



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JimGalloway Author/Editor


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