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High Diversity of Coral Reefs: How Much Time Do We Need

Coral reefs provides food and resources to people around the world / Photo by Daviddarom via Wikimedia Commons

 

Coral reefs, also known as "rainforests of the sea," are one of the most productive and biodiverse ecosystems on earth. Although it only occupies less than one percent of the ocean floor, it is the home of a number of marine species such as reptiles, crustaceans, seaweeds, bacteria, fungi, and over 400 species of fish. Coral reefs are not just beneficial to the marine life, it also provides food and resources for millions of people in different countries. 

According to the Coral Reef Alliance, coral reefs also provide humans with medicines, revenue from fishing and tourism, and even protection from storms. Other marine life forms contribute to the survival of coral reefs. For instance, fishes who specialize in eating different kinds of algae keep the corals from being smothered by their potentially deadly competitors. Some fish species such as the cleaner fish keep them healthy by freeing them from parasites. 

The Status of Coral Reefs

However, just like with other marine life forms, coral reefs are in danger. In a recent statistics by the Reef Resilience Network, about 75% of coral reefs are currently being threatened across the globe. They are experiencing an increased ocean temperature and acidity compared in the last 40 years. If not taken care of, scientists predicted that almost all reefs will be labeled as threatened by 2050 because of global and local stressors.

There are several threats that affect the biodiversity of coral reefs which are mostly man-inflicted. For instance, the demand for food fish and tourism are increasing. As a result, overfishing happens not just with the commercial fish but also in some coral reef species. This can negatively affect their ecological balance and biodiversity.  Some humans use destructive fishing methods such as fishing with cyanide and dynamite. Not only it kills specific fish species, but it also damages the coral reef habitat. In the past 10 years, fishing threats have risen by 80%. 

The demand for tourism is increasing as well. Tourists visit various countries just to have experienced what is like underwater. But with careless swimmers and divers, the coral reefs can be physically damaged. The establishment near the oceans can also produce untreated sewage and wastewater that pollutes the habitat. As a result, the growth of algae will compete with corals for space on the reef.

Moreover, coral reefs can also be affected by coastal development. Construction projects on coastal cities and towns may be built on land reclaimed from the sea. As a result, sensitive habitats including the coral reefs can be disturbed or destroyed by dredging activities. In fact, for the past 30 years, the threatened coral reefs have increased by 30%.

How Are Corals Affected by Climate Change? 

The greatest global threat to coral reef ecosystems is climate change. Due to greenhouse emissions produced by human activities, the Earth's atmosphere and ocean are getting warmer compared to the past decades.

According to the International Coral Reef Initiative, coral bleaching is detrimental to the coral reefs. It occurs when corals are getting upset in the changes in their environment such as light, temperature or nutrients. They expel the symbiotic algae living in their tissues, causing them to turn completely white. Unfortunately, its impact is increasing in frequency and intensity. Significant bleaching events are reported in 1982, 1987, and 1992. About 46% of corals in the western Indian Ocean were affected and died in 1998, the strongest sea surface warming event ever recorded. If coral bleaching will continue for the next years, it will greatly affect the ability of coral reefs to adapt and provide services. 

Additionally, ocean acidification caused by the uptake of carbon dioxide (CO2) from the atmosphere refers to a reduction in the pH of the ocean. This can have negative impacts primarily for oceanic calcifying organisms such as coral reefs.

How Much Time Do We Need?

In a research conducted by Elizabeth Christina Miller, Kenji T. Hayashi, Dongyuan Song, and John J. Wiens entitled "Explaining the ocean's richest biodiversity hotspot and global patterns of fish diversity," the researchers found out that patterns of high diversity seen in different oceans may take millions of years to happen. But it will only take a few years to be wiped out by human activities. 

According to the Science Daily, the richness of fish species and the high diversity people see today evolved simply because they had the time, not because they develop more quickly in tropical marine areas. The study, which is the first to show a direct link between time and species richness, also found out that a region should have a long-term stability to achieve high species diversity, which can take for up to 30 million years.

In proving this, the researchers used distribution data which represents 72% of all marine fishes. They used various statistical methods to determine the reasons for the species richness patterns among global marine regions. "Biogeographic reconstructions help us understand where ancestors were living at various places back in time, based on where species live today and how they are related. It's easy if you only compare two species that live in the same place, but if you have thousands of species and go back further and further in time, more ancestors come into play and things become more difficult."

In conclusion, an ample time is required to accumulate high diversity. But because of human-induced impacts, coral reefs will have a difficult time to recover. 

 

Climate change cause coral bleaching among the coral reefs causing them to turn completely white / Photo by Stop Adani via Flickr

 

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