Introduction
Coral reefs, true jewels of marine biodiversity, are in grave danger. For several decades, these ecosystems, which are home to about 25% of marine species, have been disappearing at an alarming rate. According to scientific estimates, nearly 50% of coral reefs have already been lost, and by 2050, 90% could be seriously degraded if nothing is done. Why are these reefs disappearing and what steps can we take to save them? This article examines the main causes of their decline and proposes solutions to reverse this trend.
1. The causes of the disappearance of coral reefs
a) Climate change: Global warming is the number one threat to coral reefs. Rising ocean temperatures are causing coral bleaching . Corals live in symbiosis with microscopic algae called zooxanthellae, which provide them with nutrients and give them their bright colours. When the heat is applied, these algae are expelled, leaving the coral white and starved of food. If temperatures remain high, the corals eventually die. Massive bleaching events have been observed in recent years, particularly on the Great Barrier Reef in Australia, where more than half of the corals bleached in 2016 and 2017.
b) Ocean acidification: Ocean acidification, caused by the absorption of carbon dioxide (CO2) by the seas, reduces the concentration of calcium carbonate, a mineral essential for the formation of coral skeletons. As a result, corals have more difficulty building and maintaining their limestone structures, which weakens their reefs and makes them more vulnerable to storms and erosion.
c) Pollution: Coral reefs are also threatened by various forms of pollution. Chemicals from agriculture, such as pesticides and fertilizers, cause algal blooms that suffocate corals by blocking the light needed for photosynthesis. In addition, plastic pollution, microplastics, and marine debris can harm corals by damaging their tissues and disrupting local ecosystems.
(d) Overfishing and destructive practices: Overfishing disrupts coral reef ecosystems, particularly by reducing populations of herbivorous fish that prevent the proliferation of invasive algae. Destructive practices, such as dynamite and cyanide fishing, irreversibly destroy reefs by wiping out entire ecosystems.
(e) Coastal development and mining Coastal infrastructure development, unsustainable tourism and reef mining for construction materials cause direct damage to coral reefs. Dredging and construction alter ocean currents and increase sedimentation, which smothers corals and reduces their ability to regenerate.
2. What we can do to save coral reefs
a) Combating global warming: Reducing greenhouse gas emissions is essential to limit the rise in ocean temperatures and prevent future bleaching events. This requires reducing our dependence on fossil fuels by developing renewable energy sources, such as solar and wind. The goals set by the Paris Agreement, which aim to limit global warming to below 2°C, are essential for the survival of coral reefs.
b) Protecting reefs through marine protected areas (MPAs): Establishing marine protected areas is one of the most effective solutions to protect coral reefs. These areas limit or prohibit destructive human activities, allowing corals to regenerate. Currently, about 7% of the oceans are protected, but the goal is to reach 30% by 2030. MPAs provide a refuge for corals and the marine species that depend on them, reducing the impacts of fishing and coastal development.
(c) Encourage sustainable fishing and responsible practices: Sustainable fishing practices are essential to protect coral reefs. Measures such as limiting the catch of herbivorous fish, banning destructive methods (such as dynamite fishing), and using environmentally friendly techniques help preserve reef biodiversity. In addition, raising awareness among local communities about the importance of sustainable management of marine resources can strengthen reef protection.
(d) Restoring coral reefs: Coral reef restoration projects, such as coral gardening , have emerged to try to restore damaged reefs. These programs involve growing coral fragments in underwater nurseries before replanting them on degraded reefs. While these initiatives cannot replace prevention of bleaching and degradation, they represent a temporary and local solution to strengthen reefs.
e) Reduce pollution and raise public awareness: Reducing chemical and plastic pollution is crucial for the survival of reefs. Stricter waste management policies, as well as measures to reduce the use of single-use plastics, can reduce sources of marine pollution. In parallel, education and awareness-raising among local communities and tourists are essential to encourage reef-friendly behaviors, such as reducing carbon footprints, disposing of waste properly, and adopting responsible tourism practices.
Conclusion
Coral reefs are in danger, but it is not too late to reverse the trend. By addressing the root causes of their degradation – climate change, pollution, overfishing and coastal development – we can protect these vital ecosystems for marine biodiversity and the millions of people who depend on them. Protecting coral reefs requires collective and coordinated action on a global scale, from reducing carbon emissions to establishing marine protected areas and promoting sustainable practices. Every effort counts to ensure the survival of these underwater wonders for future generations.
Scientific references:
Hoegh-Guldberg, O., et al. (2007). “Coral Reefs Under Rapid Climate Change and Ocean Acidification.” Science , 318(5857), 1737-1742. Available here
Hughes, TP, et al. (2017). “Global warming and recurrent mass bleaching of corals.” Nature , 543(7645), 373-377. Available here
Pandolfi, JM, et al. (2011). “Projecting coral reef futures under global warming and ocean acidification.” Science , 333(6041), 418-422. Available here
