Marine biologists never get tired of warning about the dangers human actions pose to one of the most amazing ecosystems on the planet, the coral reefs. The complex associations of marine organisms (plants, fish) need certain conditions to develop (temperature, water composition, light), and as soon as these conditions change, they become vulnerable to diseases, degradation and eventually death.

A study published on Thursday in the online journal Science Express revealed a troubling fact: one third of the world’s reef-building corals face extinction. Together with them, a large number of marine species could also disappear, as coral reefs are home to over 4,000 species of fish, as well as other organisms (sponges, jellyfish, sea cucumbers etc.)

The extinction of coral reefs would trigger devastating effects for marine biology, and if that’s not enough to draw attention on the matter, maybe the fact that it will also trigger serious economic consequences will.

The authors of the study found 32 percent of the 704 species of corals to be at elevated risk of extinction, and the problem extends across the globe. Phenomena such as diseases and bleaching, as well as anthropogenic disturbances are directly responsible for the growing number of coral reefs threatened with extinction.

The largest proportion of corals in high extinction were found in the Caribbean, while the Coral Triangle in the Western Pacific was found to have the highest proportion of species in all categories of elevated extinction risk. This calls for urgent conservation measures, which we humans have the power to enact before it is too late.

Anthropogenic activities are considered to be the largest enemy for coral reefs around the world. The consequences of irrational live fish trade, ocean acidification, sediments, water pollution and other harmful actions are obvious in many coral reefs today.

Most corals face extinction due to bleaching and disease, experts say, which are directly linked to the rise of water temperature at sea-surface, consequence of global warming. When temperatures go above a certain level, water composition changes, or sedimentation increases, the stress causes the corals to lose their coloration and bleach.

Some coral reefs are known to have been able to recover from bleaching, but if global warming continues, coral bleaching is likely to become irreversible, triggering the death of a large number of corals, scientists warn.

Increasing amounts of CO2 in oceanic waters, obviously a consequence of an increasing amount of CO2 in the atmosphere caused by global warming, trigger ocean acidification, which reduce calcification in corals, as well as in other marine organisms.

Coastal activities, as well as poor land management and pollution, lead to sedimentation, a phenomenon that once more change the living conditions of coral reefs, by increasing the amount of nutrients in the water. This triggers another effect, algal blooms, which take over the water and suffocate the corals.

As if these factors weren’t enough, overfishing also contributes to coral reef degradation, as it often target species that are vital to the corals’ existence.

The critical condition of corals reefs all over the world was the subject of the 11th International Coral Reef Symposium, which started off on July 7 in Fort Lauderdale, Florida. “Reefs of the future” was the theme of this year’s symposium, which highlighted the coral reef crisis and the necessity to protect them, by implementing scientific-based strategies at global scale.