Coral reefs: why are they so important?

Coral reefs, which are among the oldest ecosystems on Earth, appeared nearly 500 million years ago. They survived numerous periods of mass extinctions, including the Ice Age 440 million years ago and the Permian-Triassic boundary extinction 250 million years ago. After largely disappearing in the middle Eocene, reefs rebounded 26 million years ago, forming structures such as the Great Barrier Reef, discovered by James Cook in 1770. Currently, coral reefs are facing serious threats, such as blanching, pollution and heavy tourism. To raise awareness of these threats and promote conservation efforts, the Coral Restoration Foundation has established World Coral Reef Day, celebrated annually on June 1 since 2018.

Coral reefs – key ecosystems of our planet

Coral reefs, often called rainforests of the seas, are one of the most important ecosystems on the planet. They account for less than 0.1 percent. The surface of the ocean floor, but support about 25 percent. All marine species, including fish, mollusks, crustaceans and marine plants. This biodiversity ensures the stability of marine ecosystems, making them more resilient to environmental change.

Coral reefs protect coastlines by acting as natural barriers that dissipate wave energy and protect against erosion and storms. They are also important for local economies, attracting tourists and supporting fishing, which is a source of food and income for millions of people. These ecosystems are also of great importance to science and medicine. Chemicals produced by reef organisms are being studied to treat diseases such as cancer and bacterial infections.

Why are coral reefs in danger?

One of the most serious threats to coral reefs is global warming, which leads to an increase in ocean temperatures. We are currently experiencing the fourth global coral bleaching, which began in early 2023. As a result More than three-fifths – 62.9 percent. – coral reefs The world has been severely affected. Bleaching has affected coral reefs in all major ocean basins, including the Great Barrier Reef, the Caribbean, the Red Sea, as well as parts of the Indian and Pacific Oceans.

Human activity is a key factor responsible for rising ocean temperatures. Since 1971, the oceans have absorbed more than 90 percent of the excess heat generated by greenhouse gases, which has significantly raised the temperature of sea water. This unusual increase in water temperature is an unprecedented stress factor for corals, leading them to expel the symbiotic algae that live in their tissues. Such a process causes them to whiten. If heat stress persists for a long time, it can lead to corals dying. Consequently, prolonged exposure to elevated temperatures poses a serious threat to the survival of coral reefs.

Ocean acidification

Ocean acidification is another serious consequence of rising carbon dioxide concentrations in the atmosphere. The oceans absorb about 30 percent. _CO2 emitted by humans, leading to a chemical process that creates carbonic acid. This process results in a lowering of the pH of marine waters, which is equivalent to their acidification. Since the beginning of the industrial revolution, i.e., over the past 200 years, the pH of the oceans has decreased by about 0.1 pH units, corresponding to a 26 percent increase in acidity.

Acidification of sea water has a negative impact on corals, hindering their process of forming calcareous skeletons, which are essential for their structure and survival. Reduced concentrations of carbonate ions, which are necessary for the construction of these skeletons, make corals more susceptible to both mechanical and biological damage. In addition, the acidified environment adversely affects the reproductive processes and growth of coral larvae, posing a serious threat to marine biodiversity.

Pollution and habitat destruction

Chemicals such as pesticides, heavy metals and other organic compounds can have toxic effects on corals and other marine organisms. The presence of microplastic in the oceans poses another threat, as corals can ingest it, leading to their weakening. In addition, plastic waste not only damages corals physically, but can also serve as vectors that carry pathogens and toxins that cause disease.

Excessive fishing poses another serious threat to coral reefs. Destructive fishing techniques, such as the use of dynamite or bottom trawlers, can directly destroy coral reef structures. The elimination of key fish species that control algal populations can lead to excessive growth of algae that compete with corals for space and light.

Tourism and coastal infrastructure development are also negatively affecting these fragile ecosystems. Intense tourist traffic, especially at popular dive sites, can lead to physical damage to reefs, and sewage and waste from hotels and other tourist facilities can contribute to eutrophication of waters, promoting the growth of harmful algae. In addition, the construction of coastal infrastructure, such as ports, roads and housing facilities, often leads to water pollution and degradation of natural coral habitat.

What will happen when coral reefs disappear?

The threat to coral reefs has disastrous consequences for both marine ecosystems and us. Here are some of the key implications of their eventual disappearance:

• Loss of biodiversity – coral reefs provide habitat for about 25 percent of the world’s coral reefs. All marine species. Their disappearance could cause the mass extinction of many species of fish, invertebrates and other marine organisms;
• Disruption of food chains – As a key link in marine food chains, coral reefs play a fundamental role in maintaining the balance of ocean ecosystems. Their absence could lead to global ecological disruption;
• Coastal protection – coral reefs act as natural protective barriers, shielding coastlines from erosion and the force of storm waves and tsunamis. Their degradation would expose many coastal areas to the destructive forces of nature;
• Economy and tourism – Coral reefs are vital to many local economies, especially in the tourism and fishing sectors. Their disappearance could lead to significant economic losses, affecting the lives of millions of people;
• Fish stocks – In many communities, especially in developing countries, coral reefs are a key food source. Their disappearance would reduce access to fish stocks, exacerbating food security issues;
• Climate change – coral reefs contribute to carbon sequestration, which is crucial in regulating carbon dioxide in the atmosphere. Their disappearance could weaken the ability of the oceans to absorb this gas, thus accelerating climate change.

In the face of these threats, protecting coral reefs is not only an environmental issue, but also a fundamental issue of protecting economic and social well-being around the world.

Photo. main: LI FEI/Unsplash