By now most aquarists realize that the condition of most coral reefs throughout the world is, at best, precarious. What most people probably don't realize is that this condition is nothing new; we are in the midst of a faunal extinction event that is at least roughly equivalent in effect to the Cretaceous/Tertiary asteroid impact that killed off the larger dinosaurs (Ward, 1997, 2000). The smaller dinosaur lineages which we commonly call birds survived the ancient event, as did the mammals that were our distant ancestors, but that is another story. In any event, the present extinction event may not be as selective.

It All Began "Way Back When…"

When events are occurring around us we tend to look for a cause that is recent, and unless we find such a cause, we often dismiss the events as just part of the normal series of events that constitute life. In other words, the events are seen as part of a process that has been continuous and that is part of nature; something that has always been occurring and always will occur. In this instance, unfortunately, while the conclusion that these events have always been occurring is incorrect, the finite beginning occurred in the far distant past. The endpoint won't really occur for a long time, probably centuries, but the changes that are now occurring are hitting us at an increasingly rapid pace. We are seeing dramatic changes occurring within some marine ecosystems, including some coral reefs, from year to year. Even though the final outcome, the extinction of much of the planet's variety of life, is some time in the future, what we are seeing during the process of reaching that outcome is the alteration of virtually all marine and terrestrial communities, and particularly the destruction of the most complicated ones, the tropical rainforests and the coral reefs. Even though the outcome of the process is probably a few centuries away, the impending changes resulting in "transitional states" will be serious, substantial and will quite literally "change the world."

As the reader might expect, the vast majority of the causes of these changes are the cumulative actions of humanity. We are all familiar with the current concern about global warming, and the possibility that such changes can cause disasters for both man and other organisms. In the particular case of reef aquarium hobbyists, one disaster of import may be the impending changes in coral reefs caused by elevation of the temperature of the global oceans. The problems of global warming are serious, indeed; however, they pale ecologically with other changes that have been occurring for 10,000 or more years, but which are now both increasing in severity and becoming noticed. Unfortunately, even though we might recognize these changes, there is probably little we can do about them.

Why Can't I See These Changes?

The question naturally arises, "If these events are so severe and deleterious, how come we haven't noticed them?" To answer that question and to propose some things hobbyists can do, I will use as a series of examples, the same problem as it is manifested in several non-coral reef communities, and then I will relate the problem to reefs and discuss some options we, as hobbyists, might have.

Extinction of the Terrestrial Megafauna

What is happening today in the oceans is the logical continuation of a series of events causing a geologically recent extinction that first began in the ancient human past. Some of the best evidence for the beginning of this extinction event comes from the northern part of North America. We can conclusively date the first wave of a wholesale faunal extinction and follow its course rather nicely. It began with the arrival of man on the North American continent about 13,000 years ago. As an aside, to those students of ancient American history, I am indeed familiar with the evidence that humans may have been present in North or South America well before this time. However, if people did populate the continent at that time, they left few traces and had remarkably little effect. The same is not so for the folks who arrived from across the Bering Land bridge about 13,000 years ago. These were people who have been given the name "Clovis Point People," or "Clovis People" after the distinctive shape of their spear and projectile points first discovered near the town of Clovis, New Mexico. The Clovis tribes spread widely throughout North America over a period of a couple thousand years after arriving on the continent.

A Personal Connection with the Past

I live in the little town of Wilsall, Montana, about 90 miles due north of the center of Yellowstone National Park's northern boundary. Wilsall, like most small towns in the middle of what may be graciously called "nowhere," has no enduring claim to fame. In 1967, however, about 600 or so meters from where I sit as I type this, the oldest human burial in North America was unearthed by two men repairing an irrigation ditch. In a small cave on a north-facing hillside, they found, along with remains of a small child, over 100 projectile points and stone tools. This find, now known as the "Anzick burial site, (1, 2, 3)" after the owners of the land where it was found, has since been dated variously from 11,500 to 13,000 years ago. Now most authorities seem to accept an age of about 12,500 years for the burial.

At that time, this part of Montana was several hundred miles to the southeast of the continental ice sheet's remains, and its climate would probably best be described as "harsh." As elsewhere on the continent, the fauna was dominated by a whole array of huge animals, collectively known as megafauna. In this area the dominant mammals, or at least the ones most likely to give you pause as you walked around a bend near a river, were probably either Columbia or Woolly Mammoths; remains of both species have been found in the region. Standing over 4 meters (13.2 feet) high, these elephants were common in the area. It is still not all that unusual to find mammoth remains in the area, by the way. I have found fragments of a couple of molars, and people regularly bring similar remains to the local university for identification.

The Clovis people hunted these mammoths and other large animals using long spears tipped with finely made stone tools. Clovis spear points have been unearthed in mammoth skeletons elsewhere in the United States, and their largest spear points would be significantly oversized for most other animals. To be sure, a lot of other large animals were present at the time, such as two other species of elephants; the long-horned bison, Bison latifrons; regular bison and other herbivores including several species of sloths, horses and camels, but these hunters seemed to specialize on the mammoths. There were also large predators, such as several large cats, including at least two species of saber-toothed cats larger than modern lions; however, cats indistinguishable from modern lions also lived in the region. Along with the large cats came large dogs; in fact, the largest of all dogs, the Dire Wolf (Canis dirus) was very common throughout North America. This puppy averaged over 175 pounds in weight and had very large jaws with huge attachment areas for large muscles giving its bite tremendous "crunching" power. It obviously was well adapted to gnawing on elephant bones… and the sight of a pack of these behemoths gathering in the shadows around a campfire would have been enough to give any hunter of the time either a sleepless night, or a really exciting, albeit relatively short, portion of his night thereof.

As the Clovis people populated North America and then spread into South America, virtually all of the large mammals vanished. They became locally extinct at the leading edge of the human population. Over 60 species of animals with a body size exceeding 50 kg (110 pounds) were extirpated from these continents. In fact, by the time the Clovis culture disappeared about 7,500 years ago, the only large mammals left in their area of the lower 48 United States were two species of deer, bison, elk, moose, two species of bear, gray wolves, mountain lions and jaguars.

The vanishing of the mammalian megafauna has been known for a long time, but it has been in only the last 25 years that its true cause, human hunting (1, 2, 3), has been known. It was thought at one time that these animals vanished due to changes in the climate, but it seems clear that this is not the case. As a matter of fact, virtually the same mammalian array, without humans added to the mix, survived unscathed through the previous warm interglacial period, which occurred about 125,000 years ago. The cause of this extinction event appears to have been the skillful hunting of the first humans on these continents (Hallam and Wignall, 1997).

Similar events occurred in other areas whenever modern humans invaded an area not previously occupied by some protohumans, such as Homo erectus. Presumably the animals in these ancestral human areas first learned, and then evolved, an instinctive fear of man, the hunter. As has also occurred in the Americas, Australia and isolated islands such as Madagascar and Japan, without any ancient human ancestors, the native animals never had the chance to learn fear of man-like animals before modern man's arrival on the scene. After his arrival, most never had a chance to learn it either; they were exterminated.

After the wave of hunters exterminated the large animals, the hunters had to either alter their culture or become extinct. Given that humans are probably the most adaptable animals, such alterations came rapidly and the culture of the Clovis people vanished into the ancestral pool of the Native Americans. By the time European explorers reached North America, most of the people living there were agrarian, living in more-or-less fixed villages and practicing some sort of agriculture. Several crop species had been domesticated in eastern North America, Mesoamerica and the Andean highlands, and trade in, and information about, some of these crops had been disseminated widely. However, the continent as a whole was, in a sense, ecologically "deficient" (Diamond, 2005).

As I noted earlier, I live in Montana and "… environmentally, Montana is perhaps the least damaged of the lower 48 states…" (Diamond, 2005). But even here, those habitats that look pristine have been significantly altered by events that occurred a very long time ago. Many of the ecological niches found in terrestrial environments in other parts of the world were "vacant" in the Western Hemisphere, which likely allows for the rapid establishment of introduced species that seems to be a common occurrence. Although the large animals have been gone for thousands of years, the amount of time since their demise has been insufficient to allow the evolution of any animal to fill those vacancies. More to the point, however, it isn't just the large animals that are absent. Also missing are all of the ecological relationships of which they were a part, and any organisms dependent upon them. We have no real idea what the ecological communities that normally would have been found in North America would be like, as we have no analogues of such communities in the world today. Exactly the same situation applies to coral reefs. Today's reefs have been so perturbed for so long by the actions of humans, either directly or indirectly, that any semblance of normality is long since gone.

The Extinction of Pacific Island Faunas

There is no evidence that waves of terrestrial megafaunal extinctions seen in North America, Australia, New Zealand, Japan and Madagascar continued immediately into the adjacent marine environments. However, continue they did. It just took some time to develop the appropriate seafaring technology before they could occur. Such exploitation of the marine fauna began in the Indo-Pacific with development of the means for island colonization, and in the Caribbean with the arrival of Europeans.

The best data on the effect of humans on Indo-Pacific coral reefs come from archaeological and anthropological information. The basic pattern is one of maximal utilization of resources to the ultimate, and often total, depletion of those resources. Some examples (taken from Diamond, 2005) are in order. These examples are all from relatively small islands, and were chosen by Jared Diamond in his book to show human effects on the island's resource base; however, they just as nicely show the effects on the nearby marine environment. All of these islands are in the south central and southeast Pacific Ocean and represent the "fringes" of expansion by the world's best seafarers, the Polynesians.

The first example is Mangareva Island, which was initially settled around 800 AD. It is a dot of land in the middle of a lot of water, having only about 10 square miles of area. The maximum human population on the island was "a few thousand" people. The humans deforested the island and its adjacent reef areas appear to have been secondarily effected. The human population overran its resource base, and the population collapsed. A small population, a few hundred people, was still living there when Europeans "discovered" the island in 1797. A second example, settled about the same time was Henderson Island. It has a land area of about 14 square miles, but almost no fresh water. Its maximum human population at any one time appears to have been "a few hundred." Examination of middens (ancient garbage heaps) indicates that the inhabitants, "…disposed of tens of millions of fish and birds over the centuries.(Diamond, 2005)" The human population collapsed and was gone by the time Europeans chanced upon the island in 1606. The island has no permanent population today. The consumption of tens of millions of fish and birds, even spread over several centuries, certainly had a significant effect on nearby marine communities. The third example, Pitcairn Island, is probably best known as the refuge of the mutineers from the HMS Bounty. It was also settled around 800 AD, but is much smaller, having only about 2.5 square miles of land area. After settlement, its inhabitants rendered five of the nine native land bird species and six species of sea birds locally extinct. Late in the colonization period, edible shellfish disappeared from the middens, indicating either that the shellfish were locally extinct or that the people had lost the ability to harvest them. The island's human population collapsed and was gone by 1790.

The final example is Easter Island, which was settled around 1200 AD. This island is of greater size, 66 square miles. The estimates are that the population ranged from 3,000 to 30,000 individuals and probably fluctuated significantly from time to time. Of the original native plant species only 48 remain. The island was totally covered in dense forest at the time of Polynesian colonization. It was totally deforested, and among the 21 extinct tree species was one of the world's largest palm trees. In this case, the deforestation occurred not because the people had a need for the trees for building or food, but used them to move the immense stone heads (moai) that have made the island famous, from carving sites at Ranu Raraku to various sites along the coastline. They also used the wood for ritual funeral pyres, unlike any seen elsewhere in Polynesia (Diamond, 2005). Reconstructions show that, at the time of discovery and colonization, Easter Island probably had been the richest seabird breeding site in all of Polynesia and possibly all of the Pacific. Of 25 species of seabirds that nested there, 15 are now locally extinct and 9 remain in small remnant populations on offshore islets. Only one species still breeds on Easter Island proper. Of the six land bird species, all were driven to extinction. The removal of that many birds from ecosystems of the southeastern Pacific had not only a local, but quite likely a regional, impact. Today there are no native land birds. The human population collapsed; falling from over 20,000 to around 3,000 by 1722 when the island was first visited by Europeans. The exact dates for the sequence of the deforestation were found by coring lake samples in the caldera of the volcanoes and noting when deposits of tree pollen ceased to occur in the cores.

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Figure 1. Easter Island Changes. Left: A couple of the offshore islets where small remnant bird populations still breed. Right: Rano Raraku caldera showing the scrub brush remaining in what once was a completely forested region. Images courtesy of, and copyright by, Eric Borneman.

It Was Worse in the Caribbean…

Compared to the Indo-Pacific, humanity's effects on the Caribbean reef systems have been more recent but, if anything, far more intensive and disastrous. These include the ecological, or actual, extinction of all of the large herbivores; mostly sea turtles and manatees, but also including Queen conchs. Carnivores, such as the Caribbean monk seal and large sharks, also have been driven to either extinction or ecological insignificance. These losses have occurred over the last 500 years, with major losses occurring since 1950 to the point that all large carnivores, including the large pelagic fishes, as well as the herbivores are, if not biologically, ecologically extinct (Baum and Myers, 2004). Here biological extinction means the total absence of the species, while ecological extinction means the reduction in populations to the level where the species is ecologically insignificant.

Specifically referring to the Caribbean, Jeremy Jackson (1997), a noted coral reef ecologist, stated:

"Studying grazing and predation on reefs today is like trying to understand the ecology of the Serengeti by studying the termites and the locusts while ignoring the elephants and the wildebeeste."

He goes on to make the point that the changes in reefs have been relatively slow compared to human life spans, occurring over generational times and, as a consequence, have largely gone unnoticed.

The Slippery Slope of Sliding Baselines

Individuals in each human generation perceive the world that they observed as children to be "pristine" or normal. As Jackson again (1997) put it:

"The problem is that everyone, scientists included, believes that the way things were when they first saw them is natural. However, modern reef ecology only began in the Caribbean, for example, in the late 1950s when enormous changes in coral reef ecosystems had already occurred. The same problem now extends on an even greater scale to the SCUBA diving public, with a whole new generation of sport divers who have never seen a "healthy" reef, even by the standards of the 1960s. Thus there is no public perception of the magnitude of our loss. Another insidious consequence of this "shifting baseline syndrome" is a growing ecomanagement culture that accepts the status quo, and fiddles with it under the mantle of experimental design and statistical rigor, without any clear frame of reference of what it is they are trying to manage or conserve. These are the coral reef equivalents of European "hedgerow ecologists" arguing about the maintenance of diversity in the remnant tangle between fields where once there was only forest."

Keystone Species

Many of the changes to coral reefs that we are now seeing have nothing to do with direct human perturbation of the basic reef community, but rather the effects are due to the alteration of numbers or complete removal of "keystone" species. Keystone species are species whose actions determine the structure of an ecological community or ecosystem. First described from the rocky intertidal zone of the Pacific Northwest, the concept has been since shown to have wide latitude (Paine, 1966, 1974; Paine and Levin, 1981). The rocky intertidal zone of Washington's outer coast is comprised of a series of zones. Significantly simplified, a zone of barnacles is found in the highest intertidal zone of this region. Below this is a zone of mussels, then a zone of different barnacles, and then a zone of rugged brown algae of several species, collectively called kelp. Paine found that this characteristic zonation pattern was dependent upon the predation of a sea star, Pisaster ochraceus, which foraged in the intertidal zones for its food, either mussels or barnacles. If the sea star was removed, the whole layered system of segregated zones disappeared, to be replaced by a mat of kelp growing from the highest intertidal zone down deeply into the subtidal. What Paine found was that a very complex community was totally dependent on the actions of one of the community's hitherto presumed minor members. It is apparent that what is happening to coral reefs (and many other marine communities) all over the world today is the removal of one or more keystone species with the resultant collapse of the community structure.

In one of the more interesting ironies, it now appears that at least the offshore areas adjacent to beaches that Paine worked on were themselves altered by the removal of keystone predators, possibly about a century before he started his work in the 1960s. The predator that was removed was the sea otter, and its removal by the Russian fur traders and their enslaved Aleuts changed the marine environment all up and down the west coast of North America in what has to be yet another of the many examples of this type of perturbation. The Russians started settling along the southern coast of Alaska in the early eighteenth century and by the middle of the nineteenth century were harvesting animals and exploring as far south as central California. The primary object of their attention was the sea otter, whose fur was in high demand. In the course of their exploitation of this small mammal, the Russians effectively exterminated it.

Sea otters were absent from most of North America's Pacific coast when American colonization of the coast began in earnest in the mid-nineteenth century. By about 1920, when the first studies of the coastal communities that could be styled as being modern ecological science began, otters were pretty much forgotten. There were a few relict populations of the animals in the Aleutians and in the waters off Hopkins Marine Station in Pacific Grove, California. Along the coast, there were huge subtidal populations of several species of abalone, mostly in central Californian waters, and small localized kelp beds along the majority of the coast, although there were some larger beds in both Alaska and southern California.

By the middle of the twentieth century, the coastal intertidal communities had been studied a bit, and were largely thought to be more-or-less "pristine" (Ricketts and Calvin, 1939). The subtidal zone had effectively not been examined at all. The offshore populations of several species of abalone had been harvested for several decades, and fishermen considered them an inexhaustible resource. Initially, they were collected by hard hat divers, but by the 1960s they were harvested using SCUBA.

Around 1965, some changes started to occur that would have some rather interesting consequences. Subtidal scientific investigations of the marine environment got their start, mostly in the waters of northern Puget Sound, but also around several marine labs in central California. As a result of these studies, some of the Californian abalone were collected and were thought to be about 150 years old. These older abalone appeared to be largely senescent animals; they produced few gametes and were largely non-reproductive. Young abalone were effectively absent from the populations.

Additionally, all along the coast were found huge beds or aggregations of red and green sea urchins (Strongylocentrotus franciscanus and S. droebachiensis, respectively). As an example, in 1972 I found one "herd" of green urchins that was several hundred meters long, dozens of meters wide and at least one meter thick. It must have contained millions of animals, and as it moved across the bottom, the urchins ate everything they encountered. In the wake of this aggregation was bare, polished rock. Recently, it has been determined that in addition to the abalone being 150 years old in 1970, many of the red sea urchins were of a comparable age (Ebert and Southon, 2003).

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Figure 2. Strongylocentrotus franciscanus (left) and S. droebachiensis (right), the red and green sea urchins eaten by sea otters. The red urchins are about ten inches (25 cm) across the spines; the green one, about three inches (7.5 cm).


With the beginning of environmental awareness in the late 1960s, sea otters were protected by law. Sea otters have one very important attribute that facilitated their protection; they are photogenic and cute as the dickens. With their protection in place, southern sea otter populations rebounded and additional populations were started by transplanting animals throughout their old range. By the mid-1970s, sea otters were experiencing a resurgence in their southern populations and were spreading throughout their old range. This resulted in several quite predictable but relatively unforeseen consequences. First, given that sea otters are voracious predators, their predation on predation on sea urchins lead to an expansion of kelp beds, or more correctly, kelp forests, in the southern part of their range. Concomitantly, the industry that harvested kelp for its economically important byproducts increased dramatically. Second, the sea otters devastated the remnants of the old abalone populations. Many of these populations had already been severely reduced by abalone fishermen, and the additional predation by the sea otters, that were much more efficient than the fishermen at harvesting the abalone, put significant economic pressure on the fishermen. As a result, abalone fishermen started shooting the sea otters.

The sea otters, however, had some powerful friends in the kelp harvesters. There were reports of kelp harvesters shooting at abalone fishermen to deter them from shooting at the sea otters. As a result of this free-for-all and the resultant "wonderful" publicity, coupled with a realization that marine mammal populations all along the coasts of the United States were being devastated by fishermen and development, the Marine Mammal Protection Act was passed. This resulted, at least on paper and in near shore areas, in the federal protection of marine mammal populations. This has lead to an increase in some marine mammal populations, mostly in the southern near shore regions. Offshore populations, however, have continued to plummet.

This protection of this particular keystone species, however, appears to be a classic case of "too little, too late." Many of the California abalone populations are going extinct. This is due to predation by sea otters and fishermen coupled with poor reproduction and larval recruitment. In addition, new diseases of the abalone are being found which are wiping out the remnant populations that have been overfished (Haaker, et al, 1992). Where the otters are found, kelp beds are reappearing, often where none had been reported in "historical" times. These beds drastically change the fish populations and fisheries of those areas. These may be termed changes back to "normal" conditions, but simply put, we don't know what the "normal" conditions ever were.

All along the Pacific coast, the ecosystem of about 20 years prior to any given writer's efforts is generally regarded by that author as being "pristine" or "normal." For an interesting view of this phenomenon, I urge the readers to check out the classic book on the intertidal ecology of the California coast, Between Pacific Tides, first written by Ed Ricketts and Jack Calvin, and first published in 1939. It has been periodically revised, roughly every 10 to 15 years, by editors of varying competence and the changing vision of what is considered to be "pristine" is very illuminating.

HOWEVER, We Have NO Idea What Constitutes "Pristine" In Any Ecosystem Along The Pacific Coast.

As elsewhere, Pacific coastal aboriginal fisheries were awesomely efficient. As an example, I have done a lot of my research at the Bamfield Marine Sciences Centre, which is located in the town of Bamfield, located on the south side of Barkley Sound, Vancouver Island, British Columbia, Canada. Today, I estimate the whole population of the Barkley Sound region to be around 3,000 people. Some historians and archaeologists, however, estimate that its population 300 years ago may have ranged from about 5,000 to more than 10,000 people. The native populations in this area had an economy based on whaling and fishing the rich salmon and marine mammal fisheries surrounding Vancouver Island. Remains of the native "whaling" stations can be found, and it is evident that they harvested immense quantities of these and other marine mammals. Not all of these animals were keystone predators, but some of them surely were. In effect, the nearshore communities have been severely and significantly altered as long as man has been on them.

Finally, Coral Reefs

As in the nearshore environments and ecological communities of the temperate regions, such as the Pacific Northwest of the United States, nearshore marine communities in tropical regions have been severely "compromised." In fact, it is no exaggeration to state that most reefs worldwide are severely degraded and are on the verge of total collapse as functional ecosystems (Pandolfi, et al., 2003; Bellwood, et al. 2004). As an aside, I urge readers to examine the two short articles cited in the previous sentence; they are succinct, loaded with data on the terrible state of coral reefs in the world today and provide a good summary of the how reefs were degraded. The removal of keystone species, primarily major predators such as larger fish, turtles, crocodiles and mammals, has critically and permanently altered the systems, as has the addition of excessive nutrients and terrestrially derived runoff. Odd as it may seem to aquarists, in most coral reef areas we have no way of even knowing what the original communities were; even the earliest ecological studies of these environments began well after numerous changes had occurred. And, of course, there is no way of going back, as it appears that many of the critical animals are either ecologically or actually extinct.

Dead as a Dodo

When most people think of extinction, I suspect the Dodo is the animal that springs to mind. The Dodo was a large, flightless pigeon and was a rather silly looking bird. It looks ungainly and ill-suited to survive anywhere. Its extinction seems a reasonable fate, I think, to most people. Additionally, it went extinct on some remote island in a God-forsaken part of the world, and that means extinction is not really a problem for us here in the good old U. S. of A, right?


"When an individual is seen gliding through the woods and close to the observer, it passes like a thought, and on trying to see it again, the eye searches in vain; the bird is gone." John J. Audubon, on the Passenger Pigeon.

All Americans and Canadians might well consider the Passenger Pigeon. The Passenger Pigeon was native to eastern North America, in roughly an area bounded by the Mississippi drainage to the west, Hudson's Bay to the north and the Atlantic seaboard in the east. Yet I would wager real money that most readers from that large area have never heard of it or thought about it, even those who are bird watchers. And yet - merely 150 years ago - the passenger pigeon was likely the most numerous bird species on the planet. It lived in the deciduous forests that once carpeted North America east of the Great Plains. Individual flocks, sometimes estimated at over a mile wide and up to 300 miles long, had so many birds in them that they darkened the sky for periods ranging from hours to days. Estimates of the size of some of the subpopulations in the 19th century ranged upwards of four billion individuals. The species' total population may have reached in excess of five billion individuals and possibly comprised as much as forty-percent of the total number of birds in North America. Habitat alterations and commercial hunting changed all that.

This may be the only species whose exact time of extinction is known. The last Passenger Pigeon, named Martha, died alone at the Cincinnati Zoo at about 1:00 pm on September 1, 1914.

They are Dead but Don't Know It

In addition to the total extirpation of a species, it may be said that there are other kinds of "extinction." These conditional states are rather like way stations along the railroad line to total disappearance. The species still exists, but is significantly rarer than it once was. Such populations are often misleading as they give some hope that all is not lost; unfortunately, such hopes are generally misplaced. Occasionally, however, there is some real chance of recovery.

The first of these conditions is "economic" or "commercial extinction." This occurs when the populations get so low that it becomes economically unfeasible to harvest the animals. Often there are residual populations of a few individuals, or even large undiscovered and unexploited populations. Of course, once the unexploited populations become well-known, they are typically exterminated. Within the reef hobby, it is likely that the populations of the elegance coral, Catalaphyllia, are reaching this point in their primary collection areas. Populations of economically extinct animals may persist for a long time and sometimes may recover if conditions change.

The next step down this short staircase to the final slippery slope may be termed "ecological extinction." In these cases the populations have been reduced to such low levels that their contributions to the interactions within their community's ecological framework have become insignificant. When this occurs with keystone species, the ecological unit, either the whole ecosystem or its major subdivision, the community, will often change. The species may persist, but its role in the remnant system is generally insignificant. Often, the species then just fades away. In some cases, economic, ecological and biological extinction are related. For example, consider the Bluefin Tuna. The value of this fish, in excess of tens of thousands of dollars per fish, can retain such an economic incentive to fish that ecological extinction simply leads to total extinction and economic extinction never occurs.

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Figure 3. Although its present populations number in the thousands, the Green Turtle is still considered to be "Ecologically Extinct."

A good case in point for this would be the green turtle within the Caribbean coral reef ecosystems. Records from the 1600s document turtles as being almost unbelievably abundant in the Caribbean; estimates of their population were as high as 660,000,000 (Jackson, 1997). Present estimates of their population would be in the range of a few thousand. Green sea turtles are major herbivores on sea grasses and algae. Their demise and effective removal from the ecosystem must have had a major effect. However, that removal took place largely prior to 1900, and we have no real idea of what the reefs were like at that time.

Another recent Caribbean example of ecological extinction is the long-spined sea urchin, Diadema antillarum. These animals were very abundant in the Caribbean prior to 1983 when a disease ripped through their populations like wildfire. Small remnant populations of this urchin are now found in the area, but it has largely been removed from the reefs. This was an unprecedented population loss, as it had previously been abundant for at least several hundred years (Jackson, 1997). It has been described as the greatest epizootic that has ever occurred. The ecological extinction of Diadema has largely shifted the ecological balance of Caribbean reefs from ones dominated by corals to ones dominated by algae. And it is likely that the changes we have seen over the last 20 years are only the beginning.

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Figure 4. This image, taken in 1981, gives an idea of the abundance of Diadema antillarum in the Caribbean prior to the disease that ravaged their populations in 1983. Diadema are ecologically extinct throughout the Caribbean today.

The question, however, is not, "What will be the effects of the reduction in Diadema?" Rather, the question should be, "Why were Diadema so abundant in the first place?" Similar urchins are found on all coral reefs, but nowhere are they as widespread in abundance as they were in the Caribbean. Diadema may be, but are not always, exceptionally destructive:

"In high densities they can undercut and dislodge massive corals. If unchecked, urchins have the capacity to destroy reefs, as documented in the Galapagos Islands and elsewhere in the East Pacific where the reef structure has been eroded at rates of up to 10 kg/m2/yr (Bellwood, et al. 2004)."

In noting some of the changes that have occurred in the Caribbean, Bellwood et al., 2004 further note:

"Caribbean researchers and managers may never have seen a decent stand of Caribbean Acropora coral, a manatee or a large shark, nor can they remember the destruction wrought in the 1970s by a million sea urchins per kilometre of coastline." (emphasis added)

Putting together some of the facts about Diadema allows some speculation about their "overabundance." Given that green sea turtles are direct competitors with Diadema and given that each turtle can eat, per unit of time, about as much as 500 urchins (Jackson, 1997), it is possible that the populations of the two herbivores were "balanced" by their relative reproductive rates. Urchins reproduce very rapidly; they produce lots of gametes per year, and they have the capability of flooding the environment with their gametes. On the other hand, turtles reproduce very slowly. It takes the females as much as 40 to 60 years to reach sexual maturity (Jackson, 1997). I think it is likely that a long-term balance in their populations was originally maintained by the slightly different resource utilizations and differential reproductive rates found in the two species. If this were the case, even a slight reduction in turtle populations should result in a boost in the population of urchins and the reef population would change.

Even if the reef's original condition was one where Diadema was not abundant, the present changes in Caribbean reefs are not a "return" to "natural pre-human conditions." There have been too many other changes, including widespread overfishing of herbivorous fishes that might have helped stave off the coral-to-algal phase shift that occurred following the loss of Diadema. What we are now seeing are conditions that are probably transitional to some other "stable condition." Generally, changes of this nature are not considered beneficial, but perhaps it might not be as detrimental as it seems. Time alone will tell.

The Cause for these Effects

Most of the changes that I have discussed are, to date, independent of global warming. They are due primarily to direct and indirect human impact on specific ecosystems and have increased within the last century due to human population growth. That growth is not slowing down. Humans now utilize, either directly or indirectly, about 35% of the net primary planetary productivity (Imhoff, et al., 2004).


It means that 35% of all the solar energy that reaches the Earth, and would be useable by organisms through photosynthesis, is now used by man. As recently as a century ago, that number was probably less than 1%. This means that all of the other organisms on the planet have to subsist on only about two thirds of the energy that they had as recently as a century ago. Without that energy, many of species will die or, actually, have already perished. Furthermore, human usage of resources will continue to increase and will do so rapidly. Presently, the average North American uses about three times as much of the planet's net primary productivity as does the average Asian. However, as the standard of living increases in some previously "under-developed" countries, such as India and China, their populations' per capita use of the Earth's resources will increase dramatically.

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Figure 5. Human population from 5000BC until the present. The tiny notch in the curve at about 1400AD is the result of the Black Death in Europe and Asia. Note that the approximately 50 million deaths that occurred in World War II did not even slow the rate of increase. Present estimates are that the human population is increasing at the rate of around 200,000 people per day.

As the human use of the biosphere increases, less food and less useable habitat remain for all other life. As a result of this, a conservative estimate is that 70 to 200 species become extinct each day (Benton, 2003)! Most of these species have not been scientifically described. Additionally, most extinctions occur in areas with the highest diversity of life such as tropical rain forests and coral reefs.

Contributions of the Reef Aquarium Hobby to the Decline

Aquarists like to think that our hobby has little effect on nature, but this is not the case. Unfortunately, there is enough sloppy, non-existent or fallacious record keeping to give credence to the illusion that our hobby is not very destructive. It is difficult to get reliable data, but whenever such data are found, they paint a picture of consistent overexploitation. I think it may truthfully be said that, "We just love the reef to death."

One of the better and more recently documented examples of such tough love is the Banggai cardinalfish, Pterapogon kauderni. Its limited range and relatively small population have allowed reliable estimation of the effects on it of the aquarium fishery (Bernardi and Vagelli, 2004; Lunn and Moreau, 2004). The fish were studied intensively during 2000 and 2001. In 2001, AS A MINIMUM, roughly 118,000 fish per month, or an annual total of 1,416,000 fish, were being collected for the aquarium trade from these limited populations. The authors concluded that this harvest rate had already significantly reduced populations throughout the region and the remaining fish were smaller than they had been previously (Lunn and Moreau, 2004). Similar, but less detailed studies about the hobbyist fish trade, in general, abound; see, for example: Edwards and Shepherd, 1992; Vallejo, 1997; and Wood, 2001. These reports generally reach the same conclusions: that collection for the aquarium hobby is significantly affecting wild populations. Unfortunately for the populations concerned, the economic value of the trade means that harvesting will not be curtailed or effectively controlled. The wild populations will continue to be exploited and there is only one long-term result of such exploitation.

A Partial Solution

As ethical, responsible and concerned individuals, and as hobbyists, we need to take individual action to preserve and maintain reef animals. Notice, however, that I wrote "reef animals," not "reefs." Even "enlightened" or wealthy nations can't, or won't, take any actions to meaningfully protect either whole reefs or even partial reef environments. It is patently ridiculous to expect individuals to do what the affected nations cannot; even many individuals working together will lack sufficient pooled resources to make truly necessary changes. Additionally, regulations of fisheries or exploitation controls simply do not work, and they never have. There never has been a successfully managed long-term sustainable fishery. The usual pattern is that the rules and regulations are put into place after the fishery collapses, and the goals are both unrealistic and unmaintainable.

The dismal outcomes of regulatory plans are largely due to what has been termed, "The Tragedy of the Commons." The resources that are being exploited, in this case the animals sold in the aquarium hobby, do not belong to any one individual while they are in the natural reef. They are considered to belong to "all" the individuals in the given country or area that "owns" the reef. Local ownership of resources, such as exists in some areas, may be an exception, but problems exist with it as well. But, as has been shown time and again, what belongs to everybody, belongs to nobody and is cared for by no one. When regulations are put in place to conserve such a resource by controlling its harvest or utilization, it is always to the individual's advantage to cheat and try to get more of the resource. "After all, if I don't catch/collect it, somebody else will, and why should I let them have it?"

While it is unrealistic to expect hobbyists to try to "save reefs," they may be able to save specific species of reef organisms. I suggest the only way that hobbyists will be assured of maintaining their supplies of either the less easily collected or uncommon animals will be to grow their own. What I am suggesting here is not the mass equivalent of the "frag farms" so common in the hobby, but rather a series of distinct and concerted efforts to spawn, raise and hybridize various fishes and invertebrates. These will have to be hobbyist-initiated aquaculture activities because many of the species we find interesting are simply not attractive to larger commercial interests. Primarily, this is because there can be no fast return on investments. In effect, these are long-term projects, perhaps "labors of love" would not be too strong a phrase, and they will require specific and long-term dedication of resources and efforts.

Although these may be "driven" by the efforts of one individual, I suspect that in many cases the work will be too involved and too time consuming for one person. Such projects could become the goals of marine aquarium clubs and societies. Spawning and raising these animals are not conceptually difficult topics to tackle; however, depending upon the species, they may be logistically very difficult. This is just the sort of thing that clubs with dedicated memberships can do very well. A few examples of the types of work that could be spread out through a club's membership might include such tasks as searching through library references for information, obtaining materials from interlibrary loan, constructing racks for experimental tanks and constructing the breeding facilities themselves. Projects that involve the breeding and subsequent raising of some of the "more difficult" reef species will have to be efforts that involve dedicated tanks and systems; they really cannot be done as secondary efforts in home aquaria.

Necessary Conditions

The resources necessary for success in such an effort are many, and start with the basics. Probably the first necessary resource is the access to a large library. Most of the basic information necessary for breeding and raising many reef animals is available in print, but not online. Other basic resources include access to clean and pure seawater. Larvae do not, as a rule, grow well in dirty water, and they generally do not do well in artificial seawater. Remember, small embryos and larvae may consist of only a few cells, and they simply lack the resources necessary to detoxify the metals commonly found in excess in artificial seawaters. Even if a good artificial saltwater mixture is found, it is difficult to ensure that these mixtures will remain the same over time. Additionally, there have been problems with extraneous materials found in the saltwater. In one study, Moeller, et al, 2001, found that the artificial seawater mixture that they used, Instant Ocean™, was contaminated with di(2-ethylhexyl)phthalate (= DEHP), a plasticizer apparently found introduced to the salt by contact with the packaging materials used. DEHP material is an ichthyotoxin (= fish poison) and endocrine disrupter. Moeller and his coworkers concluded, "Because of the variability of the DEHP concentration found in Instant Ocean™, the culturing process we used was reverted from culturing with Instant Ocean to culturing with filtered Gulf Stream water obtained off the coast of North Carolina." I suggest that if the reader does proceed with these sorts of projects, it is probably a good idea to attempt to use water from an offshore source. If such water is not available, at the very least, it would be prudent to utilize a salt that is formulated for use in larval bioassays. Some salts are certified by the EPA for bioassay use and these would be a logical choice to use rather than salts that are not certified.

At all costs, as well, one must avoid contamination of the cultures with metals, either directly by contact, or by the addition of metal salts and additives. The deleterious effects of metals on both developing embryos and larvae cannot be overstated. Short-term exposures of four hours or less, at concentrations of 10 pbb, often cause problems. Generally, longer exposures to lower concentrations also cause problems. Additionally, exposure to small amounts of metals prior to spawning will often result in problems with the production of gametes and fertilization. It is also necessary to start this type of breeding experiment with freshly collected wild-caught animals. Additionally, animals that have been maintained in an aquarium with even very low levels of heavy metals may be sterilized. The relative lack of spawning events documented in marine aquaria to date may well be a result of sterilization resulting from metals exposure. A great many studies detail the deleterious effects of metals upon larvae and adult animals; see these references for more information and to get started: Heyward, 1988; Harland, and Brown, 1989; Goh, 1991; Rumbold and Shedaker, 1997; Reichelt-Brushett, and Harrison, 1999; Alutoin, et al. 2001; and Negri and Heyward, 2001.

For breeding experiments to succeed, one also needs larger animals. Sexual maturity in most animals is correlated with large size, particularly in corals. Finally, one needs to be able to feed the animals well. Unless an animal has an excess of nutrients, it will not be able to form the gametes. For animals to reproduce, they must be in the best of health. Once the animals have been obtained, and have grown to a mature size, the aquarist must provide the animals with appropriate spawning cues. Finally, it IS necessary to have both males and females for success to occur. In animals with no external sexual characteristics, such as sea anemones, it may be necessary to maintain large numbers of potential parents until the animals spawn and unambiguously inform the aquarist of their gender. Animals may be triggered into growing gametes and spawning by the use of numerous cues, primary among them are normal and seasonal changes in temperature along with corresponding changes in day length, and water movement. Many animals seem cued to spawn with lunar cycles, but spawning events do not appear to be cued directly to moonlight. Moonlight is an unreliable cue at best; however, it is correlated with the periodic and predictable changes in tidal cycles. Think what happens if a week long storm period hits and the sky is cloudy for a critical period; the cues due to changes in the light intensity are lost, but the currents related to tidal rhythms remain unchanged. Additionally, spawning is often not triggered by one cue alone, but by the combination of several cues.

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Figure 6. A pair of spawning sea cucumbers, Cucumaria miniata. Left: male; Right: female. When animal genders are not discernible from external examination, it is necessary to have enough animals spawning to ensure that there is at least one of each gender present.

Once the animals have spawned, fertilization is easy to accomplish. After that, the first major hurdle is raising the young though any planktonic stage. This will be easier if you have picked a species that has been shown to have larvae that don't feed. Such larvae often are in the plankton for very short periods; sometimes the planktonic period is as short as a couple of days. If your animal of choice has a feeding larval stage, there may be many problems involving the choice of potential foods. These are discussed in detail in numerous references such as Strathmann, 1987. The feeding larval period may be as long as a year for some Caribbean reef animals. Once the larvae have reached an appropriate size and appear to be ready to settle from the plankton, they reach a condition called "competency" which can be determined by consulting the literature on similar species. Additionally, they must be provided with appropriate substrata for settlement. If they have an appropriate substrate, the larvae will first settle from the plankton to the substrate and then metamorphose into a juvenile. Once the animals have reached this stage, all you have to do is grow them to a sellable or trading size.

As should be evident, there are a whole series of hurdles to surmount when culturing animals to an adult from a juvenile by using sexual reproduction. They are not easy, but neither are they insurmountable. The print literature will often give some good clues about how to go about the process, and there are always various researchers who will often be more than happy to assist a serious amateur or club attempting to acquire some research of this nature. In other words, this work can be done, and should be done. Only by doing such work can we free ourselves of the dependency upon, and the concomitant destruction of, the natural reefs.

If you have any questions about this article, please visit my author forum on Reef Central.

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Faunal Extinctions and Coral Reefs; What Can Hobbyists Do? by Ronald L. Shimek, Ph.D. -