Coral Reef Loss

Jesse Barnes

Corals are marine organisms that are commonly found in shallow, clear, tropical waters. These organisms secrete solid carbonate exoskeletons that, over time, build up to develop very large underwater structures called coral reefs. Not merely a product of coral, reefs serve as a habitat for many different marine ecological communities. In fact, coral reefs are home to 25% of marine organisms and are among the most diverse ecosystems on the planet. Because of this, coral reefs are frequently referred to as the “rainforests of the sea”.  Coral reefs are vital to the global economy as well as to the animal kingdom, however.  Indeed they are vital to many different aspects of the world’s economic success. The annual global value of coral reefs is estimated to be $29.8-375 billion United States dollars. Unfortunately, coral reefs are fragile and endangered mostly because of their extreme sensitivity to changes in water temperature. This sensitivity to temperature results in coral reefs being extremely vulnerable to the ever-increasing issue of global climate change.

While variations in water temperatures are the most direct threat to coral reefs, other side-effects of climate change are also affecting them. One dimension of climate change is an increase in atmospheric carbon dioxide, which gets dissolved in ocean water and raises the level of acidity in the oceans. Ocean acidification kills corals and causes the demolition of reefs. Climate change is also to blame for an increasing prevalence of cyclones and hurricanes, which can destroy reefs and their communities. Furthermore, changes in ocean temperature affects populations of keystone species, such as sharks. Population declines of keystone species disrupts delicate ecological systems connected to coral reefs, negatively impacting them. Lastly, humans are directly causing harm to coral reefs through over-fishing, blast fishing, cyanide fishing, general irresponsible resource management, and pollution, among many other negative occurrences.  Research into coral reef loss is a very active and necessary field because of the severity of these biological and economic consequences.

Global climate change causes ocean waters to vary in temperature in problematic ways. When such a temperature change occurs around a coral reef, the reef is usually damaged or bleached (organisms that inhabit the corals die, making the reefs appear white). But, exactly why does that happen? Studies have discovered that it is not just the varying temperatures that demolish reefs, it is the many side-effects of these changes, coupled along with the variations in temperature that cause dramatic damage. The primary example of this is the combination of increased CO2 levels and warm or cold patches in oceans. CO2 levels are rising in the atmosphere and the oceans, causing the oceans to become more acidic. Obviously, high acidity does not bode well for basically any living creature, especially corals and their communities. An 8-week study done by Anthony et al. attempted to learn more about how ocean acidification could affect coral reefs and, specifically, their calcification. In addition to exposing corals to varying levels of CO2, the scientists also manipulated different combinations of cool, warm, and hot temperatures along with CO2 exposure. The results were mostly hypothesized correctly, higher acidification and higher temperatures had negative effects on corals and their abilities to calcify, confirming the notion that climate and atmospheric change put together can cause exponential coral reef loss. (Anthony et al.).

The direct depletion of coral reefs by climate change is apparent, however the long term effects of varying temperatures on the organisms (from an evolutionary point of view) are not easily comprehended or often pondered. Alvarez-Filip et al. takes the studies on coral reef loss in a unique direction. Instead of examining why the coral reefs are diminishing, their article delves into predicting the future of the corals and how those ecosystems may or may not adapt to change and the factors that are causing them to degrade. Specifically, this paper analyzes how organisms that inhabit corals may be naturally selected for or against during climate change, and how consequential species turnover may affect the survival and resilience of the corals. This study calls attention to some possible long-term effects of climate change on the reefs. In this case, it is hypothesized that the species that inhabit coral reefs could be completely replaced through evolution, which could cause infinite possible changes to ocean biology (Alvarez-Filip et al.). For example, Alvarez-Filip concludes:

…the replacement of major reef-building coral species (i.e., losers) by opportunistic forms (i.e., winners) drastically reduce the capacity of the coral assemblages to deposit calcium carbonate at rates higher than the rate of erosion. These changes will therefore compromise the structural complexity of the ecosystem and the long-term stability of reef-associated biodiversity. (Alvarez-Filip et al.)

The effects of climate change and acidification on corals are fairly well-documented and accepted, but a paper by Ruppert et al. comes in on the issue from a different angle, by studying the adverse effects the ocean’s decreasing shark populations and increasing number of cyclones could have on coral reefs. Another aspect of climate change is that it also effects other species greatly, aside from coral reefs. Because coral reefs are such an integral component of ocean ecology, changes in the food web (such as the prevalence or absence of a key predator) can have massive effects on the reefs. One example of this is the fact that, due to climate change and human poaching, shark populations are severely plummeting worldwide. This completely ruins the natural balance of predators and prey, which in turn can disrupt coral reef systems radically.  Climate change has also been proven to cause an increasing frequency of cyclones, hurricanes, and other tropical storms.  Such storms cause significant physical damage to coral reefs.  Both of these examples suggest that global climate change is attacking coral reefs from numerous angles. These issues will only magnify and multiply over time (Ruppert et al.).

So, why is the loss of the world’s coral reefs something to concern ourselves with? If you do not care about the loss of critical species and habitats, then consider the economic impact of a lack of goods produced by coral reefs (mostly fish). Pratchett et al. wrote an article about the effects of coral reef loss on fish populations, fishery economy, and ocean ecosystems. Essentially, this paper considers how less coral reefs will cause a decline in certain fish populations that depend on the reefs. Consequently, certain economies will suffer. Furthermore, a lack of species that depend on reefs will disrupt those already delicate ecosystems of the corals. Because of the many symbiotic relationships in coral reef communities, such declines in organisms around the reefs will cause exponentially further reef loss (Pratchett et al.). In discussion of the economic impacts of coral reef degradation, an article by Riegl et al. analyzes the economic worth of coral reefs. They assert:

It is estimated that costs due to lost economic opportunities from destroyed coral reefs will reach US$350–870 million per year by 2015 of the annual US$3.1–4.6 billion of annual benefits from coral-reef fisheries, dive tourism, and shoreline protection services…These numbers are conservatively low and relate only to direct benefits lost. Bearing in mind that three counties in Florida alone benefit from annual revenues of circa US$4 billion, the direct and indirect financial losses associated with worldwide coral-reef degradation will have undesirable consequences to our global economy.

Taking a different approach, Kennedy et al., by using collected data and estimated projections, reveals the fate of coral reefs should humans continue to overfish and pollute the Earth with superfluous amounts of carbon without taking the necessary steps to help protect this precious resource and habitat. It also delineates certain steps that can be taken to prevent coral reefs from vanishing. For example, the best way to protect reefs is to set a fixed carbon emissions budget for every country in the world, namely those who are primary players such as China and the United States. Furthermore, the unnecessary and reckless destruction of coral reefs for things such as obtaining fish to sell as pets and irresponsible fishing methods to feed gluttonous populations must stop. However, for any plan of action to protect coral reefs to work, global cooperation is key and, sadly, that is extremely unrealistic due to the nature of foreign relations (Kennedy et al.).

Overall, the future of coral reefs look grim should humanity not change its unsustainable habits and make a substantial effort to save the reefs. In theory, the coral reefs are capable of being healed and protected, but it will most likely take the world economy suffering significantly because of the dying reefs before anything will be done about it on a large scale. The general public fails to understand the importance of coral reefs to ocean ecosystems and biodiversity, and will only take notice of economic impacts; therefore, once people realize how integral the reefs are to our planet, it may be too late to reverse the effects of our neglect. Fortunately, the science surrounding this issue is booming with new research and those who care are working diligently to save the Earth’s coral reefs.

Works Cited

 Anthony, K. R., Kline, D. I., Diaz-Pulido, G., Dove, S., & Hoegh-Guldberg, O. (2008). Ocean acidification causes bleaching and productivity loss in coral reef builders. Proceedings of the National Academy of Sciences, 105(45), 17442-17446.

 Alvarez-Filip, L., Carricart-Ganivet, J., Horta-Puga, G., & Iglesias-Prieto, R. (2013). Shifts in coral-assemblage composition do not ensure persistence of reef functionality. Scientific Reports, 3, 3486.

 Kennedy, E., Perry, C., Mumby, P., Halloran, P., Iglesias-Prieto, R., Schonberg, C., et al. (2013). Avoiding coral reef functional collapse requires local and global action. Current Biology, 23(10), 912-918.

 Pratchett, M., Hoey, A., & Wilson, S. (2014). Reef degradation and the loss of critical ecosystem goods and services provided by coral reef fishes. Current Opinion in Environmental Sustainability, 7, 37-43.

 Riegl, B., Bruckner, A., Coles, S., Renaud, P., & Dodge, R. (2009). Coral reefs: threats and conservation in an era of global change. Annals of the New York Academy of Sciences, 1162, 136-186.

 Ruppert, J., Travers, M., Smith, L., Fortin, M., & Meekan, M. (2013). Caught in the middle: combined impacts of shark removal and coral loss on the fish communities of coral reefs. Public Library of Science, 8(9), e74648.