The world’s oceans are getting hotter, higher, more acidic, and more polluted. On one hand it’s happening slowly. On the other hand it’s fast. Incredibly fast. The oceans have warmed more than half a degree in fifty years. Corals don’t like hot water. They expel their symbiotic algae resulting in bleaching, and coral death. The oceans are 30% more acidic compared with pre-industrial times. Animals with shells will struggle and disappear with the changed water chemistry. And so will the fish that feed upon them.
Fish are fleeing the heat. They are moving polewards. This is leading to loss of diversity in tropical waters, and increased competition in polar waters. The warmer water reduces productivity and rates of growth. This is happening as we expect to take more from the sea for a human population not expected to peak until mid-century.
In this address given at the University of Sydney in 2013, Callum Roberts describes the pressures on the world’s oceans and their ominous future. He says the world’s oceans have changed more in the past thirty years than during the whole of human history.
Robyn Williams: And this is the third in our present series of Science Show specials, today featuring Dr Callum Roberts, author of The Ocean of Life. He is one of the world’s real experts on fish and how their numbers have been depleted in recent years; depleted dramatically as you will hear.
I first met him when he had a fellowship at Harvard but usually you can find him far from the sea at the University of York. So let’s join Callum Roberts with an audience at The university of Sydney.
Callum Roberts: Thank you very much for such a warm welcome to Australia. I’ve been made to feel very comfortable here and I’ve certainly been having the work squeezed out of me today to try and talk about the oceans a little bit more and raise them up the agenda in this country. Not that they need raising very far, because Australia is a very proactively engaged country in terms of its marine environment.
It might seem funny to begin with a dead whale, but this is an important dead whale. It washed up on a beach still alive in New Zealand’s Bay of Plenty in December 2010, and a couple of years later, such is the pace of careful science, it was announced to the world as the first sighting of the world’s rarest whale, Mesoplodon traversii, the spade-toothed whale. It was only known from three skull fragments scattered across the southern part of the Pacific Ocean from Chile across to New Zealand, and gathered over a period of 140 years.
Nothing I think underlines the immensity of the world oceans for me quite like this, that an animal the size of a hippopotamus should have eluded us for so long, and especially one that has to come to the surface more than once an hour in order to breathe.
The enormity of the world’s oceans has long led us to think that they are impregnable and beyond harm. Aside from bits of local bother here and there like the odd oil spill or soiled beaches, or trouble with an algal bloom, the oceans themselves are, through their limitless expanse, able to absorb all of the impacts that we like to throw at them. The vastness of the sea is real and important in terms of their role in the global processes that make the world habitable, but their invincibility is illusory. And if you look out at the seas around us, everywhere you can find the imprint of humanity today, even to the depths of the deepest abyss in the oceans.
For several years past I have been researching a book, The Ocean of Life, and the subtitle for this is How our Seas are Changing. In it I explore the long history of the oceans, from the beginning of the planet right up into the present. If you take the long view, the oceans are in constant flux, they are always changing. And in the ancient world they were awash with sulphides, they were pretty much anoxic, and the choking stink of rotten eggs would have hung over every coastline.
Life probably began in these seas, around the hydrothermal vents which are spewing metal-rich compounds into the water around them. And since then over the course of billions of years they’ve endured many ups and downs as catastrophes came and went, as the world froze and then heated up, sea levels rose and receded. But in recent times—very, very recent against this geological tableau—they’ve begun to change under our influence. And what I really want to try and do is to explore some of the dimensions of human influence on the world’s oceans and what they mean for life in the sea and what they mean for us in fact. And I want to ask the question; are we headed in the right direction or should we be steering a different course?
Well, our predilection for seafood began in South Africa with the world’s first anatomically modern humans, and they occupied caves in the southern part of the country, and the rather prosaically named Pinnacle Point Cave 13B is one which preserves within its sediments the emerging humanity of ourselves. In it you can find the first jewellery, little shell beads from about 120,000 years ago, you can find improvements in the technology of hunting, the understanding of heat treatment of rock in order to make more finely pointed flake harpoons, and eventually the emergence of art, a little flake of ochre which is crisscrossed with some scratch marks on it. Archaeologists are wont to make a lot of very little, but that indeed is the world’s first art, they have convinced me. Not really. Anyway. But somebody had to do it at that point.
But more interestingly from my perspective, 140,000 years ago they were eating seafood and seafood aplenty. There were big molluscs, chunky things which were scattered across the cave floor. And then by about 70,000 years ago they were joined by fish which were probably harpooned in relatively shallow water, and then we started to develop technologies for catching them using more sophisticated means like hooks and so forth.
For most of the great sweep of human history on this planet, fish have been plentiful, we’ve never had to worry about how many there are out there or how many we take because there has always been enough to satisfy our wildest demands. Nothing I think better captures that for me than the Dutch masters’ painting still-life tableaus of fish markets in the 17th century. Within paintings like these you can see not just the incredible variety of seafood that was on offer, ranging from sturgeon to halibut to cod, wolf fish, even porpoises and seals, sea lampreys, gurnards, salmon, the whole range of fish that was on offer was simply extraordinary, but also the enormous size of the animals displayed in these paintings. This is not just mere artistic exaggeration. It is very consistent across a whole range of different artists across different decades through this period, they were painting in a very naturalistic way to depict what they saw, and it tells us something about the abundance of life in the sea.
The size of fish was simply incredible some of the time, and there are some wonderful descriptions from early accounts such as that of Olaus Magnus the Goth who was a Swedish cleric from the 16th century, and he wrote, ‘It is no trivial danger that looms over these fishermen as they pull with their hooks at fish of gigantic strength and bulk, 12 feet long, such as halibut, skate and other winged fish,’ and you think to yourself, well, that’s a bit over the top, a bit exaggerated. He goes on to say how the fishermen had to lash themselves to the masts sometimes in order to haul these things out. But then when you see pictures from the past century of enormous fish, giant halibuts, then you understand really what he meant.
Everything changed though in terms of fishing in the late 19th century with the addition of steam power to the fishing fleet, and this changed all the rules. We were now cut loose from the bonds of wind and tide that had held us for so long. We were able to travel much farther offshore, we could get fish back to market in a fresh state from much greater distances. You could go deeper down, you could drag bigger nets, you could fish round-the-clock seven days…no, six days a week, they never fished on Sundays in those days. But it was an incredible alteration in the amount of fishing power being expended.
And it was also a time of great controversy and change in the fishing industry, and that was partly because of the effect that the industry was having on the environment around it. It was, for the first time, really beginning to have an impact on the fish stocks and the fishermen started to complain, and royal commissions of inquiry were held to investigate what was going wrong and why it was taking more effort to land fish than it had before. And the inquiries usually ended up saying, well, we don’t know really, he says this, he says that, it could be either.
And so one positive thing that came out of these inquiries was the initiation of the collection of fishing statistics in 1889 in the United Kingdom, and from that a careful observer can see some interesting trends in the supply of fish. What you can see is that in 1889 with a largely sail powered fleet still, we were landing about five times more fish into England and Wales from the bottom trawl fleet, that is boats that are dragging their nets across the seabed, as we do today, which is pretty extraordinary. And that certainly caused me to pause and think about it.
But of course the amount of catch that you get is not just dependent on how many fish there are in the sea, and what you have to do is to untangle the amount of fishing power which is being expended from the amount of fish that are in the sea in order to see the pattern more clearly. In an image of the landings of fish into England and Wales it is like a mountain, it rises up into the middle of the 20th century and then it comes crashing down in the latter part of the 20th century. And within that mountain there are two deep valleys, and those correspond to the two world wars, and that is because it became too dangerous to fish, so people stopped. And if you want to interpret this pattern in terms of how many fish there are in the sea you have to find a way of correcting for the amount of fishing power going on.
And if you do that, then what you can see is that the mountain turns mainly into a kind of inverse curve and it declines very steeply initially, and there’s a blip in the middle of it, and the blip corresponds to the point after World War I when we started to fish further afield and we, once again, encountered virgin fish stocks that had never seen hook or line or trawl. And just taking that aside, the curve for the home waters is very much one that goes downwards, and we are catching 25 times less fish per unit of fishing power today as we were in the middle of the 19th century. And that tells us that we have had a major impact on the fish stocks of the seas around us.
So what was it like fishing at the beginning of that curve? Well, some of the old photographs give you an insight into it, and if you looked at the docks such as Grimsby on the east coast of the United Kingdom you can see just such prolific landings and of such enormous size that even the quayside has disappeared under the fish. There is no gaps that you can see, there are just metres-long fish, lying out there, piled in great heaps. It’s an enormous quantity of landings, totally unprecedented, impossible to find today. Those sort of scenes are consigned to history.
It’s not just in the seas around Europe though that you can find such sorry tales. There is a particularly arresting series of images taken from the same dock in Key West in different decades showing the fish that recreational anglers were landing from the day boats there. And in the 1950s there are these fantastic pictures which look like they’ve come out of The Wizard of Oz with people posing there, even with little Snowy the dog…or whatever, that’s Tintin…anyway, the fish beside them are just incredible, they are the same size as the people standing there and there are enormous numbers of them. These are animals that have been removed from spawning aggregation. Their bellies are full of eggs, they haven’t had the opportunity to spawn.
If you look a couple of decades later through in the ‘70s or ‘80s, the landings are still huge but the enormous fish have now gone. What we are still seeing is big reef fish which are being landed in plentiful numbers. And people are still having a great time when they go out angling, there’s lots for them to do, it’s a busy day, hardly time to drink beer. You get the idea.
And then fast-forward to the noughties and 2007, and the sort of landings that are coming in today would fill up a tiny fraction of the boards where they were displayed in the 1980s and the 1950s, and they consist largely of fish which are smaller than your forearm. This is utterly transformed. The one thing which is constant through all of this is that the smiles on the anglers’ faces never get any smaller. But the interesting thing is that the experience of fishing today is very, very different from the way it was in the 1950s.
The problem is that a lot of the younger generation simply don’t remember what it was like then, and so we have this shifted environmental baseline today which gives us a very different view of the condition of the oceans from the one we would have if we had all lived to 100.
And around Australia as well, these sorts of trends have been playing out over the long term. There are trawl fisheries around the east coast, for example, which have been monitored since the age of steam and where the landings per unit of fishing power and effort have really collapsed and have gone into very low levels, similar in fact to the sorts of statistics that you see from English waters.
Taken at a bigger scale, recent studies of the waters on either side of Australia show that the total landings of fish have been in long-term decline since the 1950s, and are now at much lower levels than they were then. So overfishing is not something that’s somebody else’s problem, it’s also a problem, even in countries like Australia which have managed to get their acts together pretty well to manage their fish stocks better than most.
But overfishing of course is not the only thing that is going on in the marine environment, it’s the longer standing effect that we have on the sea, but it’s joined nowadays by a number of other big problems that we are seeing accumulating into larger and larger effects over bigger and bigger areas and reaching greater and greater depths, and those are particularly climate change, pollution impacts, pollution of all stripes and varieties, not just the usual culprits of oil spills and chemical pollution or sewage pollution, but new things like noise pollution. The seas are getting a lot louder and more clamorous than they were 50 years ago or so. Nobody could write a book about the oceans today as Jacques Cousteau did in the 1950s and call it The Silent World. If you go scuba diving you will hear constant noise if you are anywhere that is popular with other divers. And then of course habitat loss is another major dimension of change that is affecting the sea.
So to global change first, seawater warming. Well, the oceans, luckily for us, have spared us frying on the land so far. You might not think that in Australia this particular year, having just endured a hellish summer. We had quite a cold winter in England as well, so a bit chilly outside, but no wildfires or 50 degree heat. But warming has been happening in the world’s oceans. Overall they have warmed a little bit more than half a degree in the surface few hundred metres over the last 50 years or so, and that warming has been patchy, some parts of the ocean have warmed more, other parts have warmed less, but you can see that the heat capacity of the oceans has increased greatly, and it has certainly ameliorated atmospheric heating over that time.
There are some kinds of ecosystems though, like coral reefs, which really don’t like even relatively small amounts of heating. Push a coral reef a degree or two above their thermal normal maximum temperatures and the symbiosis between the algae that live within the coral tissues, the corals themselves, begins to break down and become dysfunctional. The corals expel the algae, and what you have is coral bleaching. And bleaching, if prolonged, can lead to coral death, and coral death will lead to the collapse of the structure of a coral reef, so that what you end up with is rubble. Instead of having a fast bottom that more corals can attach to, you start getting mobile bottoms which are much more difficult for animals to inhabit and to recover in.
Of course warming has also produced some pretty strong effects at the poles, and in 2012 we saw the lowest ever sea ice concentration in the Arctic. And what’s happening there is that this is opening up the fabled Northwest Passage, the one that explorers gave their lives in search of in the 17th century and the 18th century, the likes of Hudson and Franklin whose expeditions were failures. Of course there was no way that they were going to get through the Northwest Passage at that time because it was fully blocked with ice all the year round. But today that Northwest Passage is opening up, so we are seeing a connection between the Pacific Oceans and the Atlantic Oceans that has not been there for probably 800,000 years or so.
And remarkably that passage is being used already, and researchers off the Israeli coast were extremely surprised by the sight of a grey whale which showed up there in 2010. Grey whales went extinct in the Atlantic in the 18th century as a result of hunting. And so to find a grey whale in the Atlantic now was of course perplexing, and the only way it really could have got in there was by losing its way out of the Bering Sea and instead of coming down the western North American coast it took a wrong turn. And you can imagine what this whale must have been thinking when it arrived in the Mediterranean and it hadn’t seen another grey whale for months; oh my God, where on earth am I, and why aren’t there any of my buddies here? I still wonder what that grey whale is doing today and I hope it’s there.
Robyn Williams: And so do we. Dr Callum Roberts at The University of Sydney, author of Oceans of Life. This is The Science Show on RN.
Callum Roberts: Another effect of the warming world is that we are seeing increasing movements of animals and plants from place to place. Geologists love to name periods of geological time as something-ocene; the Pliocene, the Pleistocene, the Eocene, the plasticine…no, that’s not quite the right one. But others have quipped that today is the ‘Homogocene’ because what we are seeing is the mixing up of all these species that have been separated through geological history. And one of the factors which is causing that increased mixing of course is that the world is warming, so the conditions are changing, there are new areas opening up, new opportunities, but there are also contracting opportunities in the back end of species ranges. So they are trying to keep within their thermal zone of happiness and avoid areas where things are getting a bit horrible.
What that means is we are going to see this movement of animals and plants, typically from the tropics where it’s getting hotter, up latitude and gradually animals and things will move their way in a polar direction. Of course what happens if you live at the pole, you can’t move. And so what we expect to see is a redistribution that will lead to loss of diversity in the tropics, because that’s an area of abandonment, and loss of diversity at the poles because that’s an area where new animals are moving into places for the first time and they are going to reorganise the communities and some species are going to lose out from those.
In between there may be winners, losers, there will certainly be change though. And one place that we are seeing change already is in Antarctica. And Antarctica is a place where it’s been a bit chilly for crabs to exist for a long time, in fact something like 40 million years. But today we see the conditions changing in such a way that king crabs are now marching their way into Antarctica. These are pretty serious predators. If you look at the ones in the Sydney Fish Market they can do some harm with those pincers. And that movement is going to profoundly alter Antarctic ecosystems. If they move all the way into these areas that are full of naive organisms that have never really come across a predatory crab before, you can imagine what the consequences might be.
And there’s another dimension to this movement of course, this is movement of species under their own power, but we of course are globalising the world, and the increased trade between different parts of the planet is bringing species from much greater distances, and it’s largely a lottery what species arrives from where. And one of them is having an impact of its own in Tasmania and that is the Pacific seastar which has been introduced from the North Pacific. It is now causing some severe impacts on the spotted handfish which is as gorgeous a fish as you can imagine, a lovely tiny little thing which is smaller than your hand, covered in slightly salmon-pink spots.
And the thing about handfish is that their fins are modified almost into hands and they walk around on the seabed and they lay their eggs on the seabed and they provide a lovely caviar feast for any starfish, and there are millions of these starfish in the Derwent Estuary. The trouble with handfish is they only occur in the Derwent Estuary of Tasmania, this particular species. And so if it goes from there it’s gone for good and there’s a real crisis for that species. It’s one that’s visible to us, we’ve spotted what’s going on, but there are probably many, many others that are happening right now out of sight and out of mind.
These movements are all very well, but from our perspective as the population grows we are obviously seeking ways to feed ourselves, and the question is; is there going to be enough seafood around in the future? Well, just when we need more food from the sea we can perhaps expects to get less, and that is because some of the changes that are taking place are going to put a big squeeze on ocean productivity, and warming up is going to squeeze productivity, acidification is happening.
Acidification happens when you dissolve carbon dioxide, one of the main greenhouse gases in the oceans, and just as it would in a can of soda, it makes the liquid more acidic and that is causing some profound changes in the sea, and they are already underway. And then we have coastal habitat loss of course, another squeeze on productivity, all of those nursery areas that are important to marine life. And overfishing itself.
In terms of the warming element of the squeeze in productivity, it is easiest to think about it if you think of the sea having two layers. At the surface you have a warm layer of water, warmed by the Sun, which is floating on a colder, denser layer of water which is deep and dark. So the warm layer at the surface has all the sunlight, so that’s where all the photosynthesis takes place and the plant growth, but that plant growth is very much constrained by how many nutrients are around. And nutrients sink from that surface layer into the deeper waters, and the only way that they can be got back is by mixing back up from below.
And what will happen as the oceans warm is that we will see a thicker layer of warm water and a hotter layer of warm water at the surface of the oceans which is going to considerably reduce the amount of nutrient mixing back up. So the amount of ocean that is becoming starved of nutrients will increase in area.
And we’ve already seen the effect of this in the middle of the Pacific and parts of the Atlantic Ocean where the ocean deserts are expanding. People have measured productivity in these areas. They are areas of extraordinary low productivity in the first place because there’s not many nutrients there, but they are becoming even less productive as the oceans warm. And over a period of years between 1998 and 2006 measurements have shown how the area of these low productivity regions has expanded. This is entirely consistent with what you’d expect from the warming of the sea water.
Warming and all of this movement of fish stocks is going to create some winners and losers in terms of fisheries, and William Cheung and his colleagues have tried to model what the effects of the changing distributions of these species that we exploit is going to do to the productivity of fisheries on a national scale. The areas of the tropics, the ones where the species are leaving because they are heating up will lose out in terms of productivity.
Some areas though will gain, in particular areas at intermediate latitudes up towards the poles. For Australia that means that you will probably lose some productivity in the northern waters, up in the Gulf of Carpentaria for example, but you’ll possibly be gaining productivity in southern Australia, already a productive place for fisheries but potentially even more so in the future.
Some of the positive effects of climate change on ocean productivity are the possibility of stronger winds which will create a movement of water away from coastal areas which has to be replaced with deeper nutrient-rich water, so up-wellings could enhance the productivity. And another thing which is going on is that warmer air holds more water and that ends up falling as rain, it’s very intense rainfall, there will be more nutrient run-off from land in the way of floods and so on, and so there could be a boost to ocean productivity in that way.
So some Australian modellers have looked forward to an era of increased productivity of the oceans which would then translate into enhanced productivity of fisheries around the country as a result of this boost to the sea’s productivity in this region. But they haven’t factored in some important dimensions to the productivity change, and one of them is that the oceans are becoming more acidic. There has been a 30% increase in acidity already since pre-industrial times, so before about 1750 or so, and we are expecting to see, under a business-as-usual emissions scenario…in other words, if we don’t do anything about the amount of fossil fuel that we burn by the end of the 21st century, we would expect to see 150% rise in ocean acidity, which is a lot.
There are very sensitive creatures to ocean acidification, and the key thing is that if you build a chalky skeleton or shell then you are going to struggle under these increased levels of acidity, because the acidity drives down the concentrations of calcium carbonate in the seawater, that makes it harder for these organisms to extract the material and put it into their shells.
At the base of the oceanic food web there are big chunks of the planktonic life which have that problem. One of them is the coccolithophores, and they create these exquisitely sculpted shells I suppose you would call them which are incredibly detailed when viewed under an electron microscope, you can’t see them with the naked eye. But you can see them from space because when coccolithophores bloom in large numbers, what you can see are these milky white trails through the water, such as off the coast of Tasmania, and they are incredibly productive and they drive the productivity of Arctic seas, of Sub-Antarctic seas, and that is where you are getting some of your ocean productivity here. So that expected fillip for productivity may never arise because if we are cutting the legs out from under this stool, the actual productivity of the plankton, then we may not see what those modellers had expected.
Acidification could create some winners as well as losers and there are some forms of plankton which importantly do not create calcium carbonate skeletons or shells, things like diatoms, for example, they build theirs out of silica, and then there are various things like dinoflagellates, cyanobacteria, viruses. The sea is chock-full of viruses. Just as a little aside, the most extraordinary nugget of information that I ever heard about the oceans was to do with viruses and that is that if you take a litre of seawater and you were to count up all of the viruses within that litre, there’s billions of them. If you multiply all the viruses around the world’s oceans and then place them end to end and stretch them out into space, they would travel not just to the Moon or to the Sun or to the edge of the solar system but 200 million light years into space. I’m not good with numbers, and when it comes to 200 million light years. I’ve done it on my calculator, I know that there is the right number of zeros there, but you still can’t get your head around how something so tiny can stretch into something so incredibly long. But there are important groups of plankton that may not benefit.
The other thing which is going to squeeze oceanic productivity is that there are really important transfer steps between the phytoplankton, the plants out there, and the animals that we prefer to eat. We’re not great at eating phytoplankton directly, so we rely on things to convert it into more palatable forms of protein. And one of these is the pteropod. Pteropods are these little snails, free swimming in the plankton, they’ve got a foot which is stretched into kind of butterfly wings. And they can swarm in their gazillions, especially in cold waters.
The trouble is that when you expose them to acidified water, to levels that are realistic for 2100 if we don’t bother to do anything about it, then they simply crumble. Their little crystal structures fall apart. You might not think we’ve eaten very many pteropods, but if you’ve ever eaten fish from sub-polar waters, wild Alaskan salmon for example or ice fish for example, then you have borrowed pteropods at second hand. So they are very important, and if they suffer, so might also the productivity.
Of course acidification is going to have a major impact on the world’s most iconic green ecosystem and one of which Australia is rightly proud. You can see something of the future. There is a window to the future in a few places around the world where you see volcanic vents bubbling carbon dioxide out through areas of coral reef. And one such is in Papua New Guinea which has been studied by scientists from the Australian Institute of Marine Science, and Katharina Fabricius who is leading that team describes how the reefs there away from these events, they look healthy and flourishing, there is enormous amounts of coral, there are fish of all sorts of varieties. But in among the areas that are acidified to levels realistic for the end of the 21st century, there isn’t that much going on. And in fact this doesn’t look like a healthy coral reef. There are a few coral heads there, there’s hardly any species, and there is lots of seaweed-covered bare rock. It’s pretty ugly. And this is what acidification could bring us later on if we don’t do anything about it.
Of course when you warm the ocean and you start melting ice then the sea levels are going to begin to rise, and one of the most chilling graphs of climate change that I have ever come across is one which looked at the predictions of how sea levels were going to rise that were made in 1990 by the Intergovernmental Panel on Climate Change. And they had their best guess of what the sea level rise would be and then they had their best case scenario which showed a lot lower rise, and then they had their worst case scenario which showed a lot higher rise.
And we’ve had since then very sophisticated tracking of sea level by satellites, and we can measure it to the millimetre very accurately. And what those measurements show is that since 1990 we have been tracking the very fastest, the worse case scenario of sea level rise which was predicted in 1990. So it’s not that we are not doing very well in terms of dealing with greenhouse gas emissions, we haven’t even tried. We are simply willy-nilly going hell for leather in releasing these greenhouse gases and it is driving change in a very rapid and problematic direction.
So now the modest ‘we can cope with it’ 30 to 40 or maybe 50 centimetres of sea level rise that was predicted is turning into metre-plus levels of sea level rise. And if you look at those satellite measurements across the sweep of the oceans, you can find that it’s not even around the world. There are some places where sea levels have actually gone down since the 1990s. There are other places where sea levels have gone up. And I think the best way to describe why that is is the title of a paper from which I drew this graph in which he called it ‘Waves in a Bath Tub: Why the Sea is Not Level’, and I think that picks it up.
I mean, you get these standing waves in some parts of the world’s oceans, which means that the sea level is rising especially rapidly, and unfortunately for you guys it’s here. Right around Australia you are seeing these incredible rapid increases in sea level. So in a period of just 15 years sea levels have gone up by 10, 12, 14 centimetres, which is just incredible. To think that the oceans are rising a centimetre a year around here, it really makes you stop and think. The sea has always been in the same place, has it not? Well, the answer is no unfortunately.
And so we respond to these challenges by defending ourselves ever more securely from sea level rise. We raise the sea walls, we harden the coasts as a result. The trouble with doing this is it puts a squeeze on ocean productivity because those coastal strips which used to be filled with important wetland habitats, mudflats, seagrass beds, mangrove forests and so on, if you put a wall in there then as the sea level rises those habitats are progressively squeezed out. And as we know they are incredibly important as nursery grounds and centres of productivity for marine life and especially fisheries. And if we lose those then we are going to see a squeeze on productivity.
In other parts of the world it’s not sea walls that are causing the issue about coastal hardening, we are also very, very rapidly increasing aquaculture around the world. And if you have an idle hour go and spend it on Google Earth and zoom in on the Chinese coastline and discover just how many hours it will take you to get from the last bit of land with no fish farms to the edge of the sea as you weave your way around endless ponds over many kilometres as it stretches out towards what used to be the seaside. I mean, forget about going for a day at the seaside, it’s not going to happen because there are all these fish farms in the way.
The other thing about the warming of seawater is that it holds less oxygen, and there are two things going on. One is that the warm water itself can’t hold as much dissolved oxygen. The other is because you’ve got this thicker layer of warm water at the surface, you’re getting reduced mixing of oxygen down into the deeper layers. And what we’re seeing as a result of that is the areas that have very low levels of oxygen are expanding, which is squeezing out the habitable space for things that demand a lot of oxygen, like tunas and billfish, for example, and sharks. So these animals that need lots of oxygen in order to maintain their active lifestyles. So another squeeze on productivity is coming from this reduced oxygen level.
There are some things though that are doing quite well as a result of reduced oxygen. Interestingly after the mass extinction at the end of the Permian, the oceans became very largely anoxic, and one of the groups that did quite well then was the cephalopods. And the closest living relative to some of those early survivors of planetary catastrophe were squids, like the vampire squid from hell. This is the most wonderful creature name, Vampyroteuthis infernalis. If I was the scientist who named that squid I would be very pleased with myself.
Of course there are also some winners in the form of much, much bigger squid off the west coast of the United States. We’re seeing huge Humboldt squid expanding their range very rapidly and they are able to hunt actively, even into these regions of low oxygen. So there’s a turnaround for the books. Instead of having big macho fishermen holding their prize tuna we have them holding up Humboldt squid. I wonder how many people enjoyed that meal when he got home with his Humboldt squid.
And so of course we can expect to see cities being taken over by enormous squid crawling out of the oceans, as imagined in this Hollywood movie from the 1950s, which I think…all movie posters are great. This one shows ‘It came from beneath the sea’ and there are tentacles everywhere and people running screaming. I love that one.
So bringing these dimensions of change together—the overfishing, higher CO2—because higher CO2 is going to make it harder for organisms to breathe in the water as well, it makes it harder to extract oxygen from the water. So it’s not just that oxygen is going down, CO2 is going up and that’s making life a lot tougher for animals in the sea. The warming itself and the low oxygen, what that does is it changes the dynamics of fish growth. And there’s a study recently by Daniel Pauly and his colleagues from the University of British Columbia which shows that as oxygen levels fall, so the maximum size of the fish is going to shrink and their growth rates are going to go down. And that is going in the same direction as the overfishing dimension which is making fish smaller and mature earlier and grow slower because fish that grow slower don’t reach the size at which they are caught so quickly. And so putting that together, what we’re going to see is that fisheries are going to become less productive over time, they going to produce fewer eggs, fewer offspring, and so these are things which lead us to be very sceptical of the predicted increases in fisheries productivity that some of the modellers are expecting to happen from their slightly oversimplified models that I’ve been showing you.
By this point you’re properly wondering if there’s any good news that I can share with you, so I do have a nugget of good news. Even if all of the oceans’ primary productivity were shut down tomorrow, it will still be a long time before we suffocate because there’s plenty of oxygen in the atmosphere, enough for more than 1,000 years, so hopefully we can get our heads around a few problems by then and we will be able to do things.
Robyn Williams: We live in hope. Dr Callum Roberts from the University of York speaking to an audience in Sydney.
Callum Roberts: By the time I had written the last sentence of my book I had come to an uncomfortable but compelling conclusion, and that is that the oceans have changed faster in the last 30 years than in all of human history and probably much, much longer. In fact not since about 55 million years ago have we seen as much change in the seas. That was a period of runaway global warming, by the way, due to enormous releases of carbon into the atmosphere, methane hydrates, frozen deposits of methane in the seabed are implicated, but nobody is exactly sure what triggered that episode of global warming. But that was a lot slower than the changes that are underway today.
If we want to see a similar speed of change you go back another 10 million years to the catastrophe that ended the reign of the dinosaurs, and then you can see the sort of rapidity of change that we are looking at, maybe a little bit more rapid than today but that’s splitting hairs, isn’t it.
So I just want to pull together some of these things to look at how the seas are changing under our influence. So the plenty of the past, which was what we have come to expect from the sea, is turning to shortage. And the big fish of old, the enormous mega-fauna that you see in old photographs and paintings is shrinking to a mini-fauna which is being driven to smaller sizes and smaller species by the intensity of fishing. And that fishing is causing enormous damage to seabed habitats so that it’s reducing their complexity, both in terms of their three-dimensional complexity but also the variety of species, and we are seeing these kinds of simplified prawn barons out there. And if you think about it, the prawns are the cockroaches of the oceans and they are things that you just can’t kill, even if you try hard to get rid of them. And then, unfortunately for a species that is gifted with a sense of aesthetics, the changes that we are seeing are shifting things from more beauty to less beauty, to poverty, and we are seeing that in coral reefs in particular.
But more worryingly, the trends taken together are moving the oceans from being very functional, supporting life on this planet, supporting our needs, processing our wastes, dealing with the problems that we create for it very nicely, to dysfunctional oceans where the whole pattern of life is breaking down, the processes that are undertaken are being compromised. And that’s leading to areas where the oceans are simply becoming uninhabitable for many species, the growing number of dead zones around the world for example. So there are all these stresses building up, all these multiple dimensions of change in the ocean.
So what are the future oceans going to look like? Well, the seers among us have looked forward to oceans that are full of gelatinous plankton. People do eat gelatinous plankton, jellyfish…I wouldn’t say it’s a delicacy in Southeast Asia but it is not offensive it least. But before we get too in love with the idea of eating jellyfish, let’s just take a leaf out of the leatherback turtle’s book. Leatherback turtles are specialists on jellyfish and they have to eat half of their bodyweight in jellyfish every day. So imagine that we fast-forward here to 2070 and you’re all sitting here with a bag of jellyfish by your side and you’re munching away through the talk just so you’ve got enough calories to stagger out of the room at the end.
Well, the problems in the ocean are really summed up because it’s all about us, it’s the huge increase in the numbers of people on this planet which is really the problem, and it’s our increasing demand for energy and energy from cheap fossil fuel sources which is driving all of these changes. Given the deadlock on the world’s political stages over climate change negotiations, we are simply not going to manage to deal with these problems anytime soon. There is going to be change built into the system for decades as we get to grips with these broader challenges, and that means that things are going to get worse for life in the sea before they get better.
To put that in context, think about the trajectory of global population growth from initiation of the Industrial Revolution in 1750 until today. Before the 20th century, none of us were able to live long enough to experience a doubling of the world’s population, but because of the way population growth has accelerating through time and has curved upwards, people alive today have seen not one but two doublings of the world population, some of the oldest among us, the most toothless out there.
And an important milestone was passed in 1977, according to some people, and that is that we exceeded the sustainable use of one planet in 1977, and we are now right out in the unknown, on the way to somewhere which is even more unknown. What is the planet going to be like in 2050 or 2060 or 2070? And in fact, if you think about it, today is the most extraordinary time in human history to be alive because the planet around us is changing faster than ever before, faster than it did at the end of the ice age or the initiation of the ice age. These are unprecedented times, and humanity is having to adapt on a scale and at a rate and in so many ways that we simply have no roadmap for, and we have to work it out as we go along.
Of course there are problems, and some of the things that are really holding us back are old ways of thinking and old ways of doing things. I know in Australia you are wedded to your coal and people think about those deposits and they look like bags of gold sitting in the ground, and like all good goblins you look at the gold and you think ‘ha ha ha’. Actually, you should take a leaf out of the goblins’ book because goblins don’t spend their gold, they simply look at it. So imagine looking at your coal and keeping it in the ground and the oil in the ground, because that’s what we’ve got to do. If we are going to avoid and avert the most problematic episode of climate change in millions of years, then we’re going to have to keep that gold in the ground.
You might wonder what is the similarity between climate change and Harry Potter. Well, there is an evil presence all the way through Harry Potter, Voldemort is out there, and just as with Voldemort, climate change is ‘he who must not be named’. Unfortunately if we’re going to confront climate change and deal with it we are going to have to start naming it, we’re going to have to bring it to the front of public discourse and political discourse in order to try to deal with it effectively.
So it’s really about changing the way we do things. And one of the things we have seen is that our most cherished places in the oceans are in trouble. The Great Barrier Reef is in growing trouble. As I mentioned, warming is driving bleaching, but that’s not the only thing that is causing stress to the Great Barrier Reef. There’s pollution from terrestrial run-off, there’s cyclones increasing in frequency, there are crown-of-thorns starfish outbreaks munching their way through the reef. And collectively these things are compromising the Barrier Reef.
And just in the last year or so we have seen a paper published that says that coral cover on the Great Barrier Reef has fallen by half since about…well, they say 27 years ago but actually most of the fall has happened in really the last 20 years, even perhaps less than that. Unfortunately it won’t be a coral Barrier Reef for much longer at this rate, even by 2030 there would be no coral cover left. Of course, as every good advertisement about a financial product says, the past is no guide to the future, et cetera, so you’d better take it as a warning because problems are happening on the Great Barrier Reef.
So what’s the remedy for all this? What can we do to future-proof the oceans around us? Well, in my view we need to really have a new deal for the oceans, a new relationship with them. Australia actually is forging that new relationship pretty quickly. It’s moving along on the right direction in domestic policies, it’s creating networks of protected areas, it’s getting to grips with fisheries management in a way, and that really is some of the fundamentals of what we can do to future-proof them.
So what would the elements of a new deal for the oceans be, a new way of managing them? Well, more protection and more of the highest form of protection, areas that are off limits to exploitation. So the best available science suggests that if we close something like 30% of the oceans to exploitation we are going to see the biggest benefit across a wide range of different measures of benefit. But we can’t just carry on in the rest of the oceans trashing them and destroying them with destructive fishing methods. So we need to fish less in most places, and by fishing less, using less destructive gear, we could land more catch by building populations back up to more productive levels.
And there is a place in the sea that we shouldn’t be fishing at all, and in fact it has been a stopgap for us in many places because fish stocks have gone down in the shallow more accessible waters and as that has happened governments have encouraged people to go offshore and deeper down. And in the deep ocean we are encountering ecosystems that are profoundly incapable of maintaining any sort of productive fishery because the pace of life there is just too slow. So we shouldn’t be fishing in the deep sea at all.
And instead of the sort of aquaculture that we’ve seen to date, something which is adding to the problems of the oceans by taking more from it in the way of wild fish to feed the farm fish, creating pollution, creating introductions of exotic species, we need a blue revolution in aquaculture which is going to solve those problems and produce a much more sustainable outcome for us.
Those coastal habitats that we’ve neglected and derided over the years, the fly-infested swamps that we’ve drained at the first opportunity, we built malls over, we’ve turned it into agricultural land, those are important, and they will become increasingly important as the sea level rises and challenges areas of coast. And then finally we need less pollution of all types, we need to de-stress the oceans in order to give life the chance to see through these difficult times ahead.
Australia is a maritime nation. It was peopled from the sea, it has the most extraordinary diverse planetary real estate in terms of its marine biodiversity, going all the way from the torrid tropics through to the ice-bound coast of the Antarctic. You are incredibly lucky. But with that good fortune comes responsibility to yourselves to manage it well but also to the rest of the world who look to you to manage these seas, to protect them for future generations.
And I’m very glad to say that that is what people are doing in Australia and that I come at a very opportune time where the management plans are being finalised for this incredible world-class network of Commonwealth marine protected areas around this nation. And also we are seeing the filling-out of a state-wide network of marine protected areas in the inshore waters that is currently under construction. So you are going in the right direction, but must do better. We must all do better if we are going to have the oceans see through the coming crisis and if the world is going to continue to be habitable for us. So, thank you very much.
Robyn Williams: Thank you Callum. Professor Callum Roberts at the University of Sydney. He’s author of Oceans of Life and it contains staggering pictures her referred to just now of giant fish in markets back then, compared to the tiddlers we see now. Dr Roberts is from the University of York in the UK.
Marine Conservation Biologist
The University of York
York, North Yorkshire
Callum Roberts at The University of York:
The Ocean of Life:
The Unnatural History of the Sea:
• Kim Booth: Seal deaths risk future of aquaculture In Question Time today, Greens Primary Industries spokesperson Kim Booth MP said reports of widespread seal deaths on salmon farms risked creating a consumer backlash and brand damage to an expanding industry. “The aquaculture industry relies on our clean, green brand being genuine, and the death of so many seals on salmon farms threatens the future of that brand,” Mr Booth said. “With public money currently raining down on the aquaculture industry like confetti, the Minister should be applying conditions to any financial assistance requiring the industry to clean up its act.”
• SMH: Obama unveils sweeping climate plan “The question is not whether we need to act. The overwhelming judgment of science, of chemistry and physics and millions of measurements, has put all that to rest,” said Mr Obama. “So the question now is whether we will have the courage to act before it’s too late.” He said 12 of the hottest years on record had been in the past 15 years and argued that gradually moving away from a carbon economy should not necessarily cost jobs.
• Guardian: Barack Obama pledges to bypass Congress to tackle climate change Obama also said he was willing to work across the political divide but would not tolerate attempts to cast doubt on the science underlying climate change. “We don’t have time for a meeting of the flat earth society,” Obama said to applause.
• John Thirgood, in Comments: So solar Power installed at next to no expense to the government or the network can facilitate massive savings against importing stinky coal power over Basslink. Further our response to the issues papers (found at saveoursolartas.org website) shows many more floored calculations that demonstrate what we see as a aim to deliberately undermine solar. Perhaps in an effort to make Tasmanians who support solar grid connect, back away and accept that an 8 cent feed in tariff is fair.