Corals, essential to marine life and the balance of the oceans, are now seriously threatened. These organisms, which form coral reefs, are the foundations of some of the richest and most diverse ecosystems on the planet. Unfortunately, corals face many threats, mainly caused by human activity. If their decline continues, the consequences could be disastrous for marine biodiversity, human communities and climate balance. This article explores why corals are in danger and why it is crucial to protect them.
1. Corals: an essential species for the oceans
Corals, although they look like plants or rocks, are actually animals. They belong to the class Anthozoa and grow in colonies composed of thousands of tiny organisms called polyps . These polyps secrete calcium carbonate, which forms the hard, calcareous structure of coral reefs.
Coral reefs cover less than 0.1% of the seafloor, but they are home to about 25% of marine species. They play a key role in the oceans by providing habitats, refuges, breeding grounds and feeding grounds for a huge variety of fish, crustaceans, mollusks and other organisms. Corals, in symbiosis with microscopic algae called zooxanthellae , produce energy through photosynthesis, which helps maintain this vibrant and rich ecosystem.
2. Why are corals in danger?
Corals face several threats, many of which are related to human activities. These threats affect not only the health of corals, but also the balance of marine ecosystems. Here are the main reasons why corals are in danger today:
a. Global warming
Rising ocean temperatures are one of the main causes of stress for corals. When water temperatures get too high, corals expel their zooxanthellae, the microscopic algae that provide them with essential nutrients. This phenomenon is called coral bleaching , because without these algae, corals lose their color and their main source of energy. If the water doesn't cool quickly, corals can't recover and eventually die.
Coral bleaching events are becoming more frequent and severe. For example, Australia’s Great Barrier Reef experienced massive bleaching events in 2016, 2017, and 2020, causing the death of a large portion of this unique ecosystem.
b. Ocean acidification
In addition to warming waters, rising levels of carbon dioxide (CO2) in the atmosphere are directly affecting the oceans. By absorbing CO2, the water becomes more acidic, a phenomenon known as ocean acidification . This increasing acidity reduces the ability of corals to form their calcium carbonate skeletons, making them more fragile and vulnerable to damage.
Acidification also affects other marine organisms that rely on calcium carbonate to form their shells and structures, such as mollusks and some plankton species. The weakening of these species leads to an imbalance in marine food chains.
c. Marine pollution
Ocean pollution, including plastics and chemicals, is seriously harming coral reefs. Plastic waste floating on the ocean surface blocks light and prevents corals from getting the nutrients they need to survive. Chemicals from agricultural activities, such as pesticides and fertilizers, cause harmful algal blooms that smother reefs.
Sediments from coastal construction or soil erosion also disrupt the delicate balance of coral reefs by increasing water turbidity, limiting the light and gas exchange needed for zooxanthellae photosynthesis.
d. Overfishing and destructive fishing
Overfishing harms the balance of coral reefs by reducing fish populations that play a vital role in regulating ecosystems. Herbivorous fish, for example, eat the algae that grow on corals. If these fish disappear, the algae can invade the reefs and smother the corals.
Destructive fishing practices, such as cyanide or blast fishing, also cause considerable damage. These methods, used to catch fish for aquariums or commercial fish, destroy coral structures and kill many marine species.
e. Unsustainable coastal development
Tourism development, construction of coastal infrastructure and rapid urbanisation of areas near coral reefs put additional pressure on these ecosystems. Uncontrolled exploitation of coastal areas leads to the direct destruction of reefs and disrupts surrounding ecosystems. Hotels, ports and marinas, for example, alter ocean currents, increase sediment in the water and contribute to local pollution.
3. The consequences of coral decline
The disappearance of corals would have dramatic consequences for marine ecosystems and for human populations. Here are some of the main consequences:
Biodiversity loss : Coral reefs are among the most diverse ecosystems on the planet. Their destruction would result in a massive loss of marine biodiversity.
Declining food resources : Many human communities depend on reefs for fishing. Coral decline would mean a decline in fisheries resources, threatening the food security of millions of people.
Increased coastal vulnerability : Without coral reefs to act as natural barriers against storms and waves, coastlines would become much more vulnerable to erosion and storms, threatening infrastructure and homes.
Economic Loss : Coral reef tourism generates billions of dollars each year. The destruction of these reefs would seriously affect the economies of many countries that depend on marine and coastal tourism.
4. How to protect corals?
Protecting corals is essential to preserving marine biodiversity and ensuring the future of the oceans. Here are some key initiatives to protect coral reefs:
Reduce CO2 emissions : Climate change is the main threat to corals. Reducing greenhouse gas emissions globally is crucial to slow ocean warming and acidification.
Create marine protected areas (MPAs) : MPAs help limit destructive human activities and protect coral reefs by providing an environment conducive to their regeneration.
Promoting sustainable fisheries : Fisheries management and banning destructive fishing practices are essential to preserving the balance of coral ecosystems.
Raise awareness and educate : It is important to educate local people, tourists and industries about sustainable practices that respect and protect coral reefs.
Conclusion
Corals are the silent guardians of the oceans, but they are now in grave danger. The loss of coral reefs would have significant impacts on marine biodiversity, coastal economies, and global food security. To preserve these precious ecosystems, it is essential to act now by reducing the impacts of climate change, protecting reefs through marine protected areas, and raising awareness of their critical importance. If we do not act quickly, coral reefs, and with them many species, could disappear.
Scientific references
Hoegh-Guldberg, O., et al. (2007). Coral Reefs Under Rapid Climate Change and Ocean Acidification . Science, 318(5857), 1737-1742.
Hughes, TP, et al. (2017). Global warming and recurrent mass bleaching of corals . Nature, 543(7645), 373-377.
Moberg, F., & Folke, C. (1999). Ecological goods and services of coral reef ecosystems . Ecological Economics, 29(2), 215-233.
