Often labelled as “rainforests of the sea” coral reefs are highly productive marine ecosystems. The reefs are made of colonies of reef-building corals held together by calcium carbonate. Coral reefs serve as the home of a great diversity of flora and fauna and are important spawning grounds for many fish species. Although such reefs cover only about 0.1% of the ocean floor, one-quarter of all the world’s marine fish species thrive there. Coral reefs are highly beneficial to humans in many ways. They are a rich source of fish. The beauty of the coral reefs attracts tourists in great numbers. These reefs also protect the coasts against flooding. It is estimated that around 500 million people globally depend on the coral reefs for their livelihood. Coral reefs also indicate the health of the global ecosystem. Unfortunately, despite their significance to humans and other life forms on earth, human activities are damaging coral reefs across the world. Below is a list of the threats to coral reefs due to human activities:
1. Climate Change
Corals live in a symbiotic relationship with algae and both benefit from each other. Algae lend color to the coral and are essential to the long-term survival of the coral. However, when water temperatures increase, corals expel the symbiotic algae. The phenomenon is referred to as coral bleaching. It is a response of the corals to stressful environments. Bleached corals eventually die. Coral bleaching is now more common than ever. Global warming induced climate change has increased the temperature of the waters of the oceans. This spike in temperatures has triggered massive coral bleaching events.
2. Irresponsible Tourism
Tourism thrives around coral reefs as tourists love to explore the colorful ecosystem of the reef. Snorkeling, diving, boating, and fishing are thus some of the popular recreational activities enjoyed at such locations. However, when tourism becomes careless and the tourists and tour operators do not pay attention to the health of the coral reefs, the situation turns ugly. Touching the reefs, stirring up the sediment in the seabed, or collecting corals are some of the activities that damage the coral reefs or disturb the species inhabiting such reefs. Many tourist resorts are built directly on coral reefs and sewage from such resorts are emptied into the surrounding water which again damages the coral reefs in the long run. Thus, if tourism is not handled with responsibility, it can destroy the coral reefs.
3. Irresponsible Fishing Practices
When fishing is unregulated and unsustainable, it can inflict great damages to marine ecosystems including the coral reefs. Fishing practices like blast fishing, cyanide fishing, bottom trawling, etc., can physically damage coral reefs or eliminate the species inhabiting such reefs. Another highly destructive practice is muro-ami which is banging on the reef with sticks to catch the fish as it comes out of hiding. Overfishing can also harm the ecological balance of the coral reef. Any disturbances in the food chain established in the reef by overfishing of one or more of its species can lead to ecological misbalance.
4. Coral Mining
Humans have found applications for nearly every object of nature including corals. Live corals are often harvested from the reefs and utilized for several purposes. Corals are sold as souvenirs to tourists. Corals are used to make bricks, fill roads or manufacture cement. These activities deplete coral reefs off their building blocks and lead to reef degradation.
Pollutants released from various sources poison coral reefs across the world. The pollutants can be as varied as industrial waste to sewage and agricultural runoffs, etc. These pollutants are either directly dumped into the oceans or enter the ocean as rivers carrying the pollutants drain into the ocean. Oil spills can also be highly detrimental to the health of coral reefs. The pollutants can affect the coral reefs in numerous ways. For example, pollutants like sewage and agricultural runoffs can increase the nitrogen level of the ocean’s waters. This can lead to an overgrowth of algae that will limit the sunlight reaching the coral reef. The result can be disastrous for all other life forms inhabiting the coral reef.
6. Increased Sedimentation
Similar to pollutants, an increased volume of sediments can also block sunlight reaching the coral reefs. The sediments can be added by various activities of like mining, farming, logging, etc. Such activities can take place on or near the coast or inland. In the latter case, rivers wash away the sediments and add them to the sea as the rivers drain into the sea.