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ECOSYSTEMS & WILDLIFE

Marine Oases in Collapse: Coral Reefs Can’t Stand the Heat

By Luisanna Carrillo-Rubio, July 2008

 

A press release issued on September, 12th, 2007, by the International Union for Conservation of Nature (IUCN) announced that corals had made their debut. Unfortunately, this constitutes the most undesirable situation for any living creature on Earth: being a debutante on the “Red List” of endangered and threatened species. The communiqué stated:

coralpicture1Corals have been assessed and added to the IUCN Red List for the very first time. Ten Galápagos species have entered the list, with two in the Critically Endangered category and one in the Vulnerable category. Wellington’s Solitary Coral (Rhizopkksammia wellingtoni) has been listed as Critically Endangered (Possibly Extinct). The main threats to these species are the effects of El Niño and climate change.

Whether in Indonesia or the Caribbean, the Galápagos Islands or Australia, coral reefs are known as the “tropical forests of the sea” due to the rich biodiversity they support and nourish. These oases of life in the world’s vast oceans are made up of very small invertebrate animals called polyps (or Cnidarians) “which create cup-like limestone skeletons around themselves using calcium from seawater” , and are classified as either hard or soft corals. Polyps are simple organisms with a mouth surrounded by little tentacles and a stomach (as can be seen on FIGURES 2A and 2B). Corals reproduce asexually by making copies of themselves through what’s called budding, to eventually create millions of identical copies forming as a result colonies (or reefs). Coral reefs “are therefore created by millions of tiny polyps forming large carbonate structures, and are the basis of a framework and home for hundreds of thousands, if not millions, of other species. Coral reefs are the largest living structure on the planet, and the only living structure to be visible from space.”

 

anatomyofpolyp_coralFIGURE 2A, Anatomy of a polyp, from the National Oceanic and Atmospheric Administration


anatomyofpolyp_coral2FIGURE 2B: close up of carnivorous coral polyps which use their tentacles out to search for food

 

An Ill-fate Awaiting the World’s Coral Reefs
The Intergovernmental Panel on Climate Change (IPCC) has already warned that coral bleaching events are going to become increasingly common among coral reefs, including the Great Barrier Reef (the world’s largest coral reef system located in the Coral Sea, off the coast of Queensland in northeast Australia), as the oceans continue to become warmer and more acidic. Bleaching occurs when the corals expel the colorful, symbiotic algae they need to eat, survive, grow, and reproduce, and all that remains is a white skeleton-like structure (see a bleached coral on FIGURE 3).

 

bleachedcoral

FIGURE 3: bleached and destroyed coral, from: http://upload.wikimedia.org/wikipedia/commons/8/83/Coral-reef-bioerosion.jpg

Coral reefs may recover from bleaching events, however if temperature and human stresses continue, their ability to recuperate is lost. Supporting this warning, the International Coral Reef Action Network (ICRAN) (http://www.icran.org/ ) admonishes that “We have already lost 27% of the world’s coral reefs. [And] If present rates of destruction are allowed to continue, 60% of the world’s coral reefs will be destroyed over the next 30 years” (http://www.icran.org/pdf/cesardegradationreport.pdf ). Today, coral reefs can be found in 109 countries and significant degradation has already occurred in 93 of these. The Nature Conservancy estimates that “Seventy percent of coral reefs may be gone in less than 40 years if the present rate of destruction continues.”

 

marinecoralAccording to the National Parks Conservation Association, coral reefs cover less than 1% of the Earth’s surface, yet they are “home to more than 25 percent of all marine life, [and] are among the oldest and most fragile ecosystems in the world.”. Their fragility lies not only in their vulnerability to human-made pressures and temperature changes, but also in the amount of time it takes for them to grow. They can take thousands of years to form, growing “at a rate as slow as 5 millimeters, and not faster than 20 centimeters, per year.” Coral reefs evolved some 200-300 million years ago, and are now facing the many threats that human activity has wrought to their existence. Most reefs today are between 5,000 and 10,000 years old and, unfortunately, “roughly one-quarter of coral reefs worldwide are already considered damaged beyond repair, with another two-thirds under serious threat,” according to World Wildlife Fund (WWF).
In the words of WWF experts, “Coral reefs have survived tens of thousands of years of natural change, but many of them may not be able to survive the havoc wrought by humankind.” The threats to coral reefs include destructive fishing practices like “cyanide fishing, blast or dynamite fishing, […] muro-ami or banging on the reef with sticks,” and the titan of all ocean destroyers: bottom-trawling (see FIGURES 5 and 6).
Cyanide fishing consists of spraying sodium cyanide on coral reefs to stunt some fish for easy capture for the aquarium trade, or for the consumption of live fish in restaurants, mostly in Hong Kong, Singapore, and mainland China. In Hong Kong, for instance, 20,000 tonnes of live reef fish is eaten annually in restaurants. The fish captured using cyanide will die soon after as a result from severe liver damage, and corals and algae die when exposed to the cyanide. In fact, WWF estimates that for every live fish caught with sodium cyanide, “a square meter of their coral reef home is killed.” While “Properly managed coral reefs can yield an average of 15 tonnes of fish and other seafood per square kilometre each year,” this is a wealth soon to be lost, as “more than 80% of the world’s shallow reefs are severely over-fished” and “58% of the world’s coral reefs are potentially threatened by human activity.”

comparisoncoralpicture

FIGURE 5 (top) 6 (bottom): bottom trawlers at work before (5) and after (6)

Over-fishing threatens coral reef communities because it disrupts the ecological balance and biodiversity, as does careless tourism (i. e., touching the reefs; dropping anchors on reefs; careless diving and snorkeling; cruise ships and tourist resorts built right by the reefs that empty their sewage into the waters surrounding coral reefs, as well as the selling of corals removed from reefs).
Pollution—in the form of industrial waste, sewage, chemicals, oil spills, or fertilizers—is also poisoning entire reefs to death. These pollutants are either dumped on the reefs’ ocean waters directly or carried from inland by rivers.
Last, but not least, climate change. Global warming is eliminating all chances of preservation and recovery of coral reefs, which cannot withstand high temperatures. Global warming “may be the final nail in the coffin for already stressed coral reefs and reef ecosystems,” concludes the WWF.

A study published by National Geographic in May, 2006, entitled “Global Warming Has Devastating Effect on Coral Reefs, Study Shows” documents that “eight years after warming seas caused the worst coral die-off on record, coral reefs in the Indian Ocean are still unable to recover,” according to marine biologists. In some areas, “reefs have been reduced to rubble, a collapse that has deprived fish of food and shelter.” As a result, fish diversity has tumbled by half in some world regions. The warming of the oceans is wreaking havoc in other ways that will continue to impair beyond recognition all marine ecosystems. For instance, a dramatic rise in jellyfish numbers in the Mediterranean Basin demonstrates the impacts that over-fishing and climate change can have on the world’s oceans. Jellyfish are now occupying the place of many other marine species, according to Ricardo Aguilar, research director for Oceana. Whereas two centuries of data indicate that the population of jellyfish swells every 12 years and remains stable between four and six years, at present the Mediterranean is entering its eighth year of massive numbers of jellyfish, which have taken the place of other fish, having no more predators , “such as tuna, sharks, and turtles” to keep their numbers at bay. In the aforementioned study, author Nicholas Graham—a tropical marine biologist at England’s University of Newcastle Upon Tyne—explains that “small but prolonged rises in sea temperature force coral colonies to expel their symbiotic, food-producing algae, a process known as bleaching […]. While the dying reefs, which turn ghostly white, can recover from such events, many do not” (see a bleached coral on FIGURE 3). He gives the following example: “In 1998 an El Niño weather pattern sparked the worst coral-bleaching event ever observed.” As a result, “over 16 percent of the world’s reefs […] were lost in that one year.” Recent research published in the Proceedings of the National Academy of Sciences “predicts that isolated reef ecosystems […] will suffer the most from global warming-caused bleaching events.” In the words of Dr. Nancy Knowlton, a marine biologist at the Scripps Institution of Oceanography in La Jolla, California, “By and large, reefs have collapsed catastrophically just in the three decades that I’ve been studying them.” Sadly, the bleaching of so many of these delicate oases will continue to be more and more prevalent since, as Dr. Knowlton notes, “corals live precariously close to their thermal limits,” and any temperature increase entails the risk of bleaching and eventually death.

A May, 2007, study of the famous Great Barrier Reef (Australia) found what researchers believe is compelling proof of the link between coral disease and warmer ocean temperatures (http://dsc.discovery.com/news/2007/05/08/coraldeath_pla.html). The research took six years and analyzed “48 reefs strung 930 miles along the Great Barrier Reef—a World Heritage site that stretches over 133, 000 square miles—the world’s largest living organism off Australia’s east coast” which is clearly visible from space. In the past, the link between ocean warming and mass disease and death, bleaching or “white syndrome” among corals had remained a hypothesis for many. Recent studies such as this one, however, demonstrate “a highly significant relationship between the two.”

 

maplocationcoral

FIGURE 7: Location of Coral Reefs on Earth

Leading researcher John Bruno (North Carolina University) states: “We’ve long suspected climate change is driving disease outbreaks. Our results suggest that warmer temperatures are increasing the severity of disease in the ocean.” The Great Barrier Reef is now at risk of “becoming ‘functionally extinct because of climate change’ that’s causing global ocean temperatures to rise. The Great Barrier Reef is not the only reef facing an increased risk of death or bleaching. In fact, “from 1876-1979 only three bleaching events were recorded, whereas 60 are on record from 1980 until 1993 […]; [and] in 2002 more than 400 events were recorded.”

Unfortunately for coral reefs and marine ecosystems worldwide the oceans are warming up more quickly than anticipated. According to a study recently published in the British journal Nature, “the world’s oceans have warmed 50 percent faster over the last 40 years than previously thought due to climate change.” It must also be noted that as sea level continues to rise as a result of global warming, coral reefs on shallow waters will struggle to survive due to the increase of ocean water above them. Most unsettling are the results of the most recent study involving Conservation International and the International Union for Conservation of Nature (IUCN) released on July 10th, 2008 (). After the scientific team examined 485 coral reef species, the conclusion was that a third of reef-building corals worldwide are now “threatened with extinction due to climate change and water pollution.” This constitutes the “first global assessment on the marine creature by 39 scientists,” and its results “are very disconcerting,” according to Kent Carpenter, lead author of the study. Roger McManus, from Conservation International, added that reef building coral species in particular are “most vulnerable to the effects of climate change.”

 

Why Are Coral Reefs So Important?

A report prepared for the Pew Center on Global Climate Change entitled Potential Contributions of Climate Change to Stresses on Coral Reef Ecosystems, stated: “One recent estimate valued the annual net economic benefits of the world’s coral reefs at $30 billion [dollars]” (http://www.pewclimate.org/docUploads/Coral_Reefs.pdf), with Southeast Asia’s coral reef fisheries alone yielding up to $2.4 billion dollars annually. In addition, “counting only the economic value of fisheries, tourism, and shoreline protection, the costs of destroying 1 km of coral reef ranges between US$137,000-1,200,000 over a 25-year period,” according to the World Resources Institute.

Southeast Asia is undoubtedly the world’s epicenter of marine biodiversity (see map on FIGURE 5), containing 34% of the world’s total area of coral reefs, 100,000 km2. Indonesia’s reefs have an economic value of US $1.6 billion annually; the Philippine reefs’ value is estimated to be annually US $1.1 billion, and combined they “hold 77% of Southeast Asia’s coral reefs and nearly 80% of threatened reefs.” As for the contributions to human populations, it is nearly impossible to attach a price tag to all the services that coral reefs provide. Firstly, fisheries depend on coral reefs, as these provide nursery space for about a quarter of the fish in the ocean. It has been calculated that one billion people depend on coral reefs for food or income from fishing. If reefs are managed in a sustainable manner, they can yield up to 15 tonnes of fish and other seafood per square kilometer per year.

Secondly, tourism yields a significant income for many countries with coral reefs. In Florida, for example, tourists visiting the Florida Keys alone generate at least $3 billion dollars a year, according to the Key West chamber of commerce. If managed sustainably, coral reef tourism could provide a significant income to poorer coastal communities. Coral reefs also play an important role in the protection of the coasts, as they are natural barriers that break the power of the waves during typhoons, tsunamis, hurricanes, and other tropical storms. Reefs also aid significantly in the prevention of coastal erosion and flooding. Lastly, coral species are unparalleled in their contributions to science and medicine, and are “already […] being used in treatments for diseases like cancer and HIV.” WWF scientists underline that “just as with tropical forests, we may continue to find the answers to medical problems in the coral reefs - so long as we can keep them healthy” and, above all, alive. All such figures and estimates alone should be compelling enough to understand the incalculable value of coral reefs. A planet with no corals would be an infinitely poorer one. As a matter of fact, upon witnessing the beauty and glory of pristine reefs and all the marine life they support, one cannot help but to feel that such ecosystems should not be senselessly destroyed. The choice is ours: what kind of a world do we want for ourselves and future generations? Oceans that are bursting with life, color, and beauty?

 

luxuriousoceancoral

Or should we continue at our present course, until all our oceans look like this?

cleachedcoral2

 

Like always, the choice and power are ours.

 

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