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,
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
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
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,
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
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
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,
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,
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 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
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
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"
As I noted earlier, I live in Montana and "
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
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
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
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
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
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).
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).
AND THESE CONDITIONS WERE CONSIDERED TO BE "NORMAL!"
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
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
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.
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
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."
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
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
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
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.
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.
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
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).
THIS IS AN ALMOST UNBELIEVABLE SITUATION!
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.
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
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
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
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
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.
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
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.
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
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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