Real Audio Recording   

presented by Melanie Stiassny

My talk this afternoon is very much a work in progress. In fact, my coauthor, Ian Harrison, is probably at this moment beavering away through the taxonomic literature, trying to decipher fish synonymies and establish valid species, and who saw the last one of its kind when and where. And it takes as its starting point, really, this article that you see here. It's an abstract from a manuscript by my colleagues, Ross MacPhee and Clare Flemming, in the Mammalogy Department.

And this work has been abstracted in the April edition of Natural History. And in that work, Clare and Ross really attempted to answer the seemingly straightforward question: How many mammal species have gone extinct within the past 500 years? Now, of course, although that's really quite an easy question to pose, as they've shown us, this isn't a simple question to answer. And, like so many other such questions, the best answer is probably: "We don't know," or, "It depends." And in this case it depends, and it depends on how well-known the group is, and how well it's really understood in a systematic and taxonomic sense. But it also depends on how stringent a series of criteria must be met before a species can be said to be extinct.

And in this paper, and the work that Ross and Clare have been doing, they've taken a very rigorous position. And that position can be characterized, really, as a species is extant until it is proven extinct. And that is a very rigorous thing to try and deal with. It's a highly demanding position. But, even using that position, Ross and Clare were able to document -- with greater or lesser degrees of certainty -- the extinction of some 90 species of mammals. They were also able to show us, and to demonstrate, how difficult a thing it is to do, to really establish an extinction, and they found it difficult, even when dealing with a group that they characterize, and we all know, as a group consisting of fewer than 5,000 living species, and for which just about all species that have existed since the Holocene are really currently known. In other words, Clare and Ross are dealing with a very well-known group of mammals, and a very well-known group of organisms, and a very well-loved group of organisms, which is mammals.

Now, such is not the case for poor Ian and myself. We have to deal with a very different order of problem. I could say "kettle of fish," but that would be a bit much. We're dealing with a far less well-known group of organisms -- and, by comparison, a group of organisms that are extremely poorly studied, and that's freshwater fish.

Now, for a group such as this, the freshwater fishes of the world, particularly when you're looking in the tropical areas, where the great concentration of diversity of freshwater fishes is found. Under these sorts of conditions, we're really going to be taking a position more not extant until proven extinct, but maybe a position extinct until proven extant, is really a more realistic way of viewing them. And, in fact, what we're going to be talking about is fishes -- if you like, you can think of them as the MIA's of the vertebrate world. These fishes are missing in action. I'm not putting in a claim for total extinction, but missing in action -- and I'm going to be talking a little bit more about that.

So it really is the case, no question, that fish species are vanishing from freshwater worldwide, and they're doing that at a frightening rate. Now, whether I can actually document for you, in every case, that these species have actually vanished or not is a moot point; they're certainly vanishing. So even if I take that sort of rather less rigorous position -- so extinct until proven extant -- I can't actually come up with a list for you, a list of the number of species of freshwater fish that have been lost from the planet.

Now if I could, of course, it wouldn't make a very good talk anyway, but I cannot do it. And, really, in some ways, what my talk today is going to be is a sort of explaining the reasons why I can't do that -- why I can't present you with a list. And talk about making a virtue of necessity, I guess I'm doing it.

First of all, before I get onto that, I'm going to interrupt myself, and to remind those of you here who haven't been sort of lambasted by me in the past on talks of this nature about the dimension of the problem and the order of the threat that the freshwaters of our planet are actually facing at the moment.

Now, the first thing that I would say is that water, freshwater, is an extremely rare commodity. And this graphic -- and I'm going to really rush through this stuff, because I really do have a lot to say -- this graphic is really pointing out one thing, and it has to do with human consumption of freshwater. And looking at this lower bar here, within the past -- between 1940 and 1990 -- while world human population doubled, human water consumption quadrupled. And there's no question that we are now, as a species, utilizing -- we're right up there at the upper limit of utilizing this resource of freshwater. It's a very rare commodity. And, in fact, we, as humans, are entering into an intensifying competition between our use of freshwater and the use of freshwater for all of the organisms that live in it. And I'm going to talk about that in a minute, briefly, also.

The other point about these freshwater habitats that I'm going to be talking about is really summarized by saying there is very, very little of it. This planet should be called Planet Water -- we all know that. We're in the Hall of Ocean Life -- 97.5% of the earth's water is marine. It's seawater. It's only 2.5% of the earth's water is actually freshwater -- but of that 2.5%, very, very, very little of it's actually available as freshwater habitat for organisms to live in and for us, as a species, to utilize. This graphic shows you the partitioning of the rest of it: 69% is ice; etc., etc. It's just .3% of that 2.5% of the world's water that is actually freshwater -- and freshwater in the form of lakes, rivers and wetlands -- so the functional freshwater in our planet. That's a tiny fraction of the world's water -- it's less than a hundredth of a percent of the world's water. So there's very, very, very little of this very, very precious commodity.

The other thing to be said about that freshwater habitat is that it is the ultimate island. We've been talking about islands in a lot of the talks here today -- the loss of species on islands. Well, freshwater is the functional analog -- it's the island par excellence; it's an island of water surrounded by land, instead of an island of land surrounded by water. And this very insular nature of freshwater ecosystems I think is really highlighted by this graphic, which is taken from the World Conservation Monitoring Centers' data on, actually, mollusk extinctions.

If you look at mollusk extinctions worldwide -- and this, I think, is since 1600, I'm not exactly sure -- but, anyway, you'll see that 80% of mollusk extinctions are on islands, and they're of terrestrial forms. So that terrestrial mollusks living on islands, 20% -- and here they all are, just stacked right up in central and eastern United States -- 20% of mollusk extinctions are continental, but they are in freshwater; those are freshwater mollusks that we've lost there. All the rest are terrestrial, on islands. So I think this graphic really sort of illustrates the real parallel between freshwater systems on continents and island ecosystems generally.

So now I'm going to talk a little bit about fishes, how many they are. And I'm going to use fishes -- because, basically, fishes are the ambassadors for freshwater. It's already been alluded to that we know so little about invertebrate distributions and numbers, by comparison. Fishes are really what we've got -- they're the sort of miners' canaries of these freshwater systems.

Now, the first thing I should say, I guess, is that there an awful lot of fishes on the planet. And we know a little about some of them, but we know virtually nothing about most of them. In fact, we hardly have that much of an idea how many fish there on the planet. And if you look at this graphic -- which sort of plots between from '76 to '94 the actual increase in numbers of species of fish that have been recorded on our planet -- this sort of evens out to about 300 species of fish are discovered each year; 300 a year. Now, that's quite an amazing rate, and that's a rate that's stayed more or less constant for about 17 years, during the time that this has been charted in this way.

What that sort of stability of increase seems to imply -- and I think there's a consensus about this -- is that the limit to the discovery of new fish species is not how many there are out there. It's: How many people are actually qualified to go out and actually identify these new entities? And it's actually been said, suggested in a wonderful paper whose title is "Have Fish Had Their Chips? The Dilemma of Threatened Fishes" -- which I think has to be one of the nicest titles I've read for a while -- that one of the main factors, and this is obviously hyperbole, but one of the factors threatening fishes worldwide is actually the threat to systematic ichthyology. That is to say, the threat to the expertise that can really give us the very basic data that we need before we can institute any programs of conservation, or even know how many of these animals are extinct.

One thing that you should perhaps notice about this graphic is actually how many of these species of fishes are freshwater fishes. In fact, it's almost 50% of all living fishes are freshwater fishes. Now, given that fishes -- you add all the other vertebrates up together, all of the mammals, all of the birds, all of the reptiles, amphibians, etc. -- add them all together, you have about the same number as you have fishes. Actually, a bit less. Now, half of all fishes are freshwater, so that works out that a quarter of all vertebrate biodiversity -- i.e., freshwater fishes -- living in less than one-hundredth of a percent of the earth's water means a tremendous concentration of biodiversity in these very, very vulnerable habitats.

Okay -- just going on, then, a little bit, to what we think we know, or what we don't know. In fact, the rate of discovery of new species, as I tried to point out, is pretty amazing, and that's particularly true in the tropics. And if I just take these three examples, very, very quickly, it gives you a sort of taste of the unknowns, as it were.

A study in the Cross River, which was a reasonably well-collected river in Cameroon, a study in 1992 -- this is a study based on the reexamination of museum material throughout the world, so material in museum collections -- revisional study, as well as going out into the field, in the Cross River, and making more collections. That increased the total of fish known from the Cross River by 73%, from the tally before that study. Similarly, a work in Sumatra -- it has increased totals of fishes from Sumatra from 272 up to about 400. In Western Borneo, Kalimantan, Roberts has increased the total from 150 to 290 species. There are still incredible unknowns with respect to the freshwater biotope.

Let's look a little -- very quickly, very briefly -- at what it is we think we do know. Well, we have publications like this. This is CLOFFOA -- the Checklist of the Freshwater Fishes of Africa -- a tremendously important document. It's really just a listing of the species, with information on synonymy distribution, etc. Now, according to CLOFFOA -- which is a wonderful starting point, if you want to sort of delve into the freshwater fauna of Africa -- according to CLOFFOA, there is probably considerably more than, but at the moment 2,780 African freshwater fishes listed in there. But, for the great majority of them, all that we know about those fishes is really that name, and a specimen sequestered somewhere in a museum. We know very, very little about the distribution or the biology, or anything of those organisms.

Just to take an example -- the bagrid catfishes of Africa -- a very, very important group economically and ecologically. Of the bagrid catfishes, 17 genera, 80% of those are known only from the type material -- material that the original description was made on. So there really is, in a sense, some of the things that we think we know, we actually really don't know that much at all. Yet despite all of this ignorance -- I mean, the other side of the coin is that it's already painfully evident that the losses in these very fragile freshwater habitats are already profound. And while the statistics on extinction are yet to be forthcoming, the figures on endangerment and attrition of these faunas are really staggering -- and I'm just going to quickly run through some of them.

North America -- North America is actually very interesting. I said most of the fish biodiversity is concentrated in the tropics, and that's true. North America is actually much richer than it should be, for all sorts of historical reasons, given its location on the globe. In North America, some 30 to 35% of all North American native fishes are considered to be at risk -- that's some 364 species currently at risk, and that's quite clearly an underestimate. In Europe, with its long history of population industrialization, the situation's even worse. And continent-wide -- well, estimates diverge quite considerably, but estimates between 40 to 80% of all native European fishes are in urgent need of some form of protection.

The situation in the tropics -- again, we know much less about it, but we also know things are pretty bad there. Peninsula Malaysia -- only 45% of the freshwater fish species that have historically been recorded in peninsula Malaysia have ever been found again -- so only 45%; 55% gone. Singapore -- more than 30% of the species found in the 1930s have never been recovered since that time. In Mexico, in 1960 or the mid-1960s, only about 36 species of Mexican fishes were in any sort of danger or were extinct; by the mid-1970s -- i.e., 10 years later -- that figure had risen to 123. The acceleration of these numbers and these problems are very, very clear, and I could go on and on and on about them.

It's been suggested that these highly diverse aquatic ecosystems are among the planet's most vulnerable. It seems that once perturbated, they deteriorate at a faster rate than their terrestrial counterparts, and, certainly, some of the data that we have has suggested that that's true. For example, in North America, of the 221 taxa for which an approved recovery plan has been instituted, only 4% of aquatic species, versus 20% for terrestrial species, have demonstrated any sort of improvement in status at all. So it does seem to be that, once you're in trouble, you're in big trouble.

The vulnerability and loss of freshwater species is undoubtedly profound, and the reasons for it are unambiguous, and they're clear. Contemporary -- I'm talking about the contemporary situation. We have no data whatsoever for what was happening to fish. I noticed that there were no fish, apparently, in New Zealand -- no freshwater fish in New Zealand. We have no data whatsoever about what's been happening in this sort of pre-, early times.

The machinery of extinction today is very, very, very clearly driven by people. It's driven through habitat modification, through the introduction of exotic species, through overharvesting, through pollution, through hybridization. As human populations burgeon worldwide, all of these problems become starker and starker, and more and more intense.

There is no question, however, that some extinctions of freshwater fishes have been natural. They haven't been human-induced; and I have many examples of those. And I'm just going to, I think, give you one, because it's one of my favorites. I hope you can see this charming little chap at the top there, Rhizosomichthys totae. If you can see him, you'll see that he has all of the charm of a naked mole rat, but without any of the social graces. I believe they're not social animals.

This animal had the misfortune -- oh, actually, there's a little aside on this beauty. My coauthor pointed out that this is a very unusual fish, in the sense that it's the only fish that we know of -- in its original description it says that it burns very well. And you'll see that -- well, it's a bad slide, but this is a cross section through the beast, and there he is -- and he's got this wonderful sac of fat all around him, so it burns very well.

Anyway, it was, as is the case for a large number of freshwater fishes, totae had a very restricted distribution -- and, actually, that would be a very interesting statistic to look into. Unfortunately, we know too little about fishes, really, to be able to get it. But I think, looking in terms of the areas -- the ranges of freshwater fishes, compared with, say, marine fishes -- I mean, off the top of one's head, one knows that freshwater fishes tend to have much more restricted distributions. But it would be nice to actually quantify that.

But, anyway -- old totae here was limited in his distribution to Lake Tota in Colombia -- and, unfortunately, there was a large earthquake on a mountain that was sitting very scenically on the edge of the lake, slid into the lake, and the lake is now tarmacked-over, and this fish is no more. So that's an example, or one of the examples, of a naturally occurring extinction.

However, most of the others are not naturally occurring at all. And I mentioned the main factors that are contributing to the loss of freshwater biodiversity, and there they are, arrayed in this graphic here -- the anthropogenic causation of extinction and endangerment. And you'll see that two of them -- now, you'll see that the totals here add up to more than a hundred. So the point of this graphic is: There is very, very rarely a case where an extinction can be attributed to one factor. It's nearly always a combination of factors that are the causation. And that's actually sort of what makes it so pernicious and so difficult, is because you clearly see multiple factors operating together, weakening the system, until one thing is going to be the straw that breaks the camel's back -- and then you get this catastrophic loss. I mean, that seems to be a pattern that sort of begs an explanation, but I think this is the explanation -- things seem to be fine, and then suddenly things are not fine. And you see a crash and your animal's gone. And I think it's through this combination of factors.

But let's just look very, very quickly at the first two -- habitat loss and introduced species -- and it really will be quickly. Habitat modification -- now I don't have time to dwell on this one, but, of course, we all know about what's happening to our planet. We all know about land conversion. We all know that croplands, pasture, forest plantations, etc., are replacing the habitats. And on this graphic I've just singled out a couple of places, with a couple of statistics, for the rates of land conversion, and they are incredible.

One thing to note -- say, for example, Bangladesh. Eighty-one percent of its land has already been converted. But the other figure in there, that Bangladesh is the third most densely species-rich country in the world, in terms of freshwater fishes. So 81% of its land area has been converted, yet it's the third-richest freshwater fish habitat in the world. It's interesting to note, actually, that freshwater patterns fish diversity do not always match -- or, in fact, they rarely match -- those that you more commonly hear for terrestrial organisms.

Anyway, land conversion. We all know about it, it's terrible, and it quite obviously impacts freshwater ecosystems. But what's actually considerably more pernicious, in terms of endangerment for extinctions in freshwater, is not necessarily land conversion -- chopping down forests, etc. -- it's actual physical impact on flow and drainage of water worldwide.

Now, of course, humans have been modifying the world's water, the world's freshwater, for centuries, but, really, in the last 50 years we've seen a real acceleration of human intervention with, basically, the world's hydrologic cycle. In fact, it has been said -- and I think we could all be excused for believing it -- that humans are simply an invention of freshwater to get itself moved around the planet.

Just think about dams. According to the World Registry of Dams, by 1968 more than 12,000 large dams were built on major rivers worldwide. And lest you think that the age of great pharaonic works of building dams is over, bear in mind that some 50 new dams are completed each year worldwide. There is -- and again, this is a quote -- "No work of man violates nature so completely or so irrevocably as a dam." And that's really true. If you look worldwide at what we've done to the world's, the globe's water, it's been estimated by the year 2000, 60% -- a full 60% -- of the world's river flow will have been diverted, drained, canalized, or perturbated in some way. And that has had profound effects -- more profound, actually, than simple land conversion on freshwater ecosystems.

The second major, major contributor -- and this is something we've been hearing a lot more about in this talk -- is the effect of introduced species. Introduced species in freshwater is a huge problem. Again, I can't dwell on it -- but since the mid-19th century, there have been 1,354 documented cases of introduction of exotic species into virgin freshwaters -- and this is just the documented stuff. It involves 140 countries and 237 species have been moved all over the globe, and nearly always to the detriment of native populations and native ecosystems.

You are all, I'm sure, familiar with the incredible loss of species, vertebrate species' biodiversity in Lake Victoria. The disaster's quite well-known. And, in fact, in terms of the number of fish species that have been lost in Lake Victoria, this is the largest human-induced extinction of vertebrate fauna in living memory. The numbers are -- it's still not even clear how many have been lost, but we're talking numbers of upward of a hundred species have been lost in Lake Victoria.

The reasons are complex. Again, it's a combination of all sorts of things. It's a combination of increasing human populations around the lake, overfishing, increasing agricultural loads into the lake. But the straw in this case that broke the camel's back was the introduction of this large predator, the Nile perch -- wiping out literally scores of species of cichlid fishes, some of the most interesting and extraordinary vertebrates on the planet. All of them gone. And in terms of, you know, lists of extinct things -- I mean, Ian and I have found ourselves becoming really rather like the Grim Reaper, when we discover that, you know, we've found an extinct species -- and then somebody finds it somewhere. Or we find it's also present in another lake. We've actually been disappointed because our list is cut down. But, hey, listen -- we've got Lake Victoria, so our list is going to be longer than just about anyone else's.

Victoria. A great disaster. Lake Lanao, in the Philippines, another very similar story. On a smaller scale, but, nonetheless, equally poignant -- and Ross is giving me the eye, so I'm going to get through that one. But there's just one more that I do want to say something about -- this one, the Middle East.

This is an interesting one, Ross, and I really will -- I've got about two minutes to go over it. As Ross has pointed out -- Ross and Clare have pointed out in their sort of listing of extinction -- one of the big problems really is our lack of understanding of the taxonomy and systematics of various groups. So a lot of the dispute on how many species are actually extinct or not often hinges on taxonomic questions. And this is sort of a rather a nice example, and I will end with it.

But we have a situation where I'm dealing with a genus called Tristramella. Tristramella was, in fact, what the fisherman in the Sea of Galilee were fishing for. I mean, if anywhere needs loaves and many more fishes, it's the Middle East. The situation of freshwater fishes in the Middle East is in a very, very bad way.

But Tristramella historically -- we had a species, sacra, in Lake Tiberius; a thing that was called simonis simonis in Lake Tiberius; we had a thing that was called simonis intermedia in Lake Huleh, up here; and we had a thing that was called simonis magdalenae in the swamps and pools around Damascus. Well, the swamps and pools around Damascus are a thing of the past, and it was thought that magdalenae was a thing of the past -- that this was an extinction. However, a recent revision looked at it and said: You know what? Based on the information from museum specimens, magdalenae is actually a junior synonym of intermedia. So you know what? We've suddenly resurrected magdalenae. It's not extinct -- it's actually alive and well, and living in Lake Huleh. So that was where the taxonomy resurrected something that was extinct.

You go to Lake Huleh -- unfortunately, Lake Huleh was drained for agricultural purposes in 1957. So suddenly, again, this creature, which was magdalenae resurrected, has now been sunk, because that's now extinct. Along with it, with the draining of Lake Huleh, we lost an endemic cyprinid, Acanthobrama hulensis; we lost a loach, an endemic loach, galileus. All of it gone, all of it history.

Part of Lake Huleh has actually been reflooded, and fish are back in it, but what was put back in it was zillii, which is an introduced species, which has been causing havoc throughout the globe.

I think I better stop there. I could, as I guess you can imagine, go on and on, but I will stop there. And any questions will be entertained later. Thank you very much.

Stiassny bio
Harrison bio