Often referred to as the “rainforests of the sea”, coral reefs are some of the most fascinating and mysterious ecosystems on Earth. Occupying less than 2% of the ocean floor, they are home to a quarter of all marine species; mollusks, crustaceans, sponges, fish, and worms are only a few of the thousands of creatures that depend on reefs for their survival.
Coral reefs have survived and thrived thousands of years of natural change but now this underwater paradise is being threatened.
The greatest threats to coral reefs and their habitats are:
Destructive fishing practices
Destructive fishing techniques such as cyanide, dynamite (blast fishing), muroami, bottom-trawling and other methods are highly unsustainable for coral reefs. These practices often result in habitat destruction, reduction of reef fish and other important species that contribute to the balance of the coral reef ecosystem.
Healthy ecosystems can produce up to 35 tons of fish per square kilometer each year, therefore, their existence and conservation is very important.
Overfishing occurs when more fish are harvested than the population can reproduce naturally. This process leads to major changes in the ecosystem and the fish reproduction cycle. For example, overfishing of herbivorous fish is harmful for the corals because they graze algae to support coral settlement and growth.
Coral reefs generate billions of dollars for host countries through tourism industry and fisheries. In countries where coral reef conservation is not a concern, tourism pressure is a major threat to the very environment on which the industry depends.
Careless swimmers, divers, and boat anchors often inadvertently destroy coral reefs by pushing or holding them. Also, poorly managed septic waste from resorts leaks out into the ocean, causing damage to the fragile corals.
Currently, 2.5 billion people live within 100 km of the coast, increasing the pressure to coastal ecosystems. Coastal development connected to construction, mining, and the tourism sector can lead to drastic impacts on coral reefs. In coastal areas where space is limited, construction projects are often built on land reclaimed from the sea. Coral reefs are adapted to waters with low nutrient content, and areas where land development disturbs the natural water flow, nutrients can reach the reefs causing even more degradation.
Corals are not able to survive if the water temperature is too high for longer periods of time. Global warming has already resulted in increased levels of coral bleaching.
When water temperature is greater than the tolerance threshold, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to lose their colorful pigmentation. At this stage corals are under immense stress and are subject to mortality.
Events such as bleaching could be the final nail in the coffin for already stressed coral reefs and reef ecosystems.