5. Bram

Biologist Bram Langeveld is the Curator at Het Natuurhistorisch, Rotterdam’s Natural History museum.

I met Bram in the ‘Picked Up, Dredged, Hammered’ exhibition space at the museum on Sunday 2nd April 2023.

Bram - In 1990 basically the government decided that ‘okay – this is the coastline right now’ and then every year following this there was a survey comparing the situation at the time against that of 1990, and we should be renourishing the beaches. Generally every single beach in the Netherlands, especially this part of the coast is ‘nourished’ once every three years, so there are these modern extensions that are quite stable, and it basically amounts to over 12 million cubic metres of sediment that is dredged from the North Sea – it must be dredged from at least 20 metres of water depth, generally 20 to 60 kilometres off-shore – and as you know like, if you build a sandcastle on the beach and you dig a trench too close to it, the castle will collapse into it, that’s similar. So that’s basically what they do. There are some exceptions. In very cases they decide they are not going to try and maintain or reference the 1990 situation, they will do it on one of these modern islands that have a more natural system – also they know that on these modern islands the situation changes rougly every six years from natural erosion to natural accretion, so if it is eroding they know in the next ten years it will start basically nourishing itself.

Matt - That’s an interesting system. Natural systems of erosion and accretion are familiar on the East Yorkshire – North Lincolnshire coastline too. Because of the current the tide slices and chops away at the clay of the Holderness coast really rapidly but it also shifts silt and sand down south of the river where it is deposited and accumulating. Retreating in one sense and growing in another.

B

That’s similar, yes, and what we see on these modern islands where the wind carries material from south to north, so we see erosion in the south and then accretion in the north. From the Atlantic, the current is sort of being funnelled – between Norway and Scotland basically makes a natural funnel into the North Sea, however if you were to block this area, as in the idea that has been proposed to build this enormous dam, then you do would not have the added strength of a large mass of water, because it tends to facilitate this funnel shape.

Of course, they are some discussions now here in the Netherlands about how much longer we can keep this up and most say until about 2100. Even with the fastest sea level rise we predict we should still be fine but then the tricky part is the province of Zeeland, which is a delta region where the dams have been built – they may be the first ones to really struggle because they were once designed to easily still manage in 2100, with this bandwidth of variation that they expected, but we are really are climbing towards the maximum of that. I’m really curious how this area will develop over the next 50 years, because it’s not just that once the dams have broken their mouth it’s also that as long as the sea level keeps rising, for example the saltwater infiltrates the rural areas, and right now they are experiencing sub-optimal soil conditions because it’s simply getting too salty. So there are some farmers already who are trying to find new crops to grow, that actually thrive in these changing conditions, but it’s not like potatoes or things they are used to growing. They are trying to innovate. But yeah, we will see. Generally, there are some voices that say we should make Winterswijk which is further inland, the capital – and I do think at some point we do need this serious discussion about how much longer can Amsterdam – any anything in the west – be sustained but at what cost? Of course, it is possible to sustain those places but if you start to nourish 100 million cubits of sediment per year in order to do this then how much is that going to take?

M

And maybe there are other global factors too that interfere with those plans, things much broader like global population levels and resource scarcity that are at play in parallel to concentrated areas of activitiy focused on preserving specific regions of coastline with national and political pressures.

B

Yes. Here in the Netherlands, we are struggling with rising sea levels in general but if you look the poorer areas, they are in way more trouble than we are – overall the Dutch situation is not that bad – yet. 

Over here we have some fossils that have been collected – a kind of timeline arrangement so these are about 400 million years of age – these are all glacial erratics, from the North – Scandinavia –

M

Very, very similar to what I would pick up on the beach - similar age, bit older possibly… again a result of that current pattern.

B

Yes – these are very much the same, from hundreds of kilometres away and transported in the same period. These fossils are mostly found in Groningen and North Holland.

In the case of these corals here from the carboniferous, they are retrieved from hundreds of metres of depth actually in coal mines, where of course it is economically viable to explore at least in the early half of the 20th century. Up until about 1974 I think, and then this changes due to cheaper imported coal from areas where either the pay was a lot less or the coal was actually at the surface itself so you don’t have to excavate at the same depth.

M

There is of course that really interesting interface between coal mining and geology – I mean, the first or most detailed early mapping of the geology in the UK was done by William Smith in the early 1800s, and I’m fairly certain he got most of his data from co-operation or working closely with coal mining interests. Facilitated by industry, changing the shape of the landscape ad moving around huge quantities of natural material.

B

Absolutely – it’s still that way here in the Netherlands. There is actually a law that says if you make a deep borehole, you must sample and make this data available and at the disposal of research to be put to all kinds of uses. For the past three centuries, coal was so important – I mean we are basically stood here right now talking about this, in this building, because of the industrial revolution – without that we would probably still be farming or something. So it has involved great, great economic benefits and really increased our understanding, but I’m quite afraid that in the next three centuries we will pay the price. And then I wonder, was it all worth it? I’m not sure.

We have some fossils here of small reptiles – these were not dinosaurs but were related to dinosaurs, and there are small bones, sometimes even complete skeletons, from around 240 million years ago, a period of time when Germany and the eastern part of the Netherlands were covered by a very large and very shallow sea. The Netherlands and Germany were basically at about 30° north – so they were right at the desert area. And it’s very shallow very salty sea water which evaporated every once in a while, so it was like a terrible place to live, basically surrounded by desert.

Then later we find cretaceous chalk and there are some very shallow quarries that are now closed but in the past you find turtles, mosasaurs, shark teeth, and also echinoderms, nautilus, crustaceans, shells – so it’s really rich in tropical fauna, about 67 million years ago.

M

It really plays with our perceptions of time thinking about animals in particular, I think. When you see representations of the Holocene flickering back all the way back through to the Cretaceous it’s almost like this reverse warming stripe chart – I’m really interested in the problem of recency, and what it is that we believe to be defaults or normals.

B

In terms of the North Sea – if you look at the past two and a half million years it’s the exception – the rule is it not being a sea, is it being land – is it being exposed – and that already most people have trouble understanding that, but it is what it is. The same if you look at the climate for the past 65 million years, we have been in like an ice house climate, and global temperatures have just been plummeting, and right now we are likely increasing again but we are still within the bandwidth of what we’ve seen for the past 2.6 million years. So if you just look at that perspective then it’s like, what are we all worrying about? But the thing is that now the rate of change is higher and we don’t know where it’s going to end. Right now we’re not slowing down anymore, so how high will it get? And then if you look back at the 5, 6, 7 degrees maybe higher and see the thermal maximum well that’s something to really worry about. Generally, if you compare today to the Cretaceous of course it may have been a bit colder but not that much, and global sea levels were significantly higher.

Later there are still a few sites in the Netherlands where it’s kind of warm/temperate so a little bit warmer than today and we’re sort of on the tipping point of the North Sea basin, it was rising and then it reaches a tipping point from about 10-12 millions years ago. You begin to find a lot of shark teeth in this area too from this time.

M

Hans said that I should ask you about shark teeth…

J

Ah okay! So the thing is that, shark teeth in general, they are normally collected in the Netherlands from the Pliocene and Miocene deposits, or in Zeeland where you can find them near the surface. They are not found in any significant quantity right here on the beach for example, because those deposits are way too deep, however what we do find are shark teeth of the Great White. These 22 specimens here were all collected in one year by one collector. It’s actually a lot – this collector, she is probably the most active collector of shark teeth and has a way of finding these, but overall, at least 500 specimens were found over maybe the last couple of decades, all on the beaches quite close to Rotterdam. And that simply does not fit with the Miocene or Pliocene age. So, then you come to think that they either transported by rivers by the sea from Zeeland, or they must be younger. So, we’ve looked into that and it seems that the abundance already makes this transporting or reworking seem unlikely, because if you look at how often they occur on these South Holland beaches and on the Zeeland beaches it is roughly the same. Normally when you have a fossil appearance and you get a reworking, very rarely a specimen gets transported away, so they would be much more rare. In many cases they are actually much better preserved here than they are in Zeeland. They seem fresher, and that cannot be the case – fossils get worn down as they travel. So this basically yielded that conclusion that these fossil shark teeth – from Great Whites – on our beaches here, are not from the Pliocene, they must be significantly younger. And then there are two options – they are either from the Eemian, so about 120,000 years ago, or from the early Holocene, about 9000 years ago. Or it could be 8000 or 7000 years ago.

M

And we certainly don’t associate Great Whites with living or migrating this far north…

B

Yes and if you consider their ecological preference they like water temperatures of around 14 degrees or higher – I think the range is around 14 to 21°, that’s their preference – although of course they can live in like 6° water and in certain deeper areas of the Atlantic they sometimes do that, but if you look at where they prefer to be it’s around 14° higher. And right now, we are just about reaching that temperature again in the North Sea, so it really seems like it would be suitable for them. Of course, they have been under tremendous pressure from overfishing, and they are a slow species to recover because they are very late to reproduce, and then the North Sea itself right now is obviously very densely used for all kinds of purposes, so it could be that there are too few of them to even reach here or they do not seem to cope with all of these pressures and the things we are doing in the North Sea.

M

And sharks are notoriously resilient if you consider how long they have been around, but in the last 500, 1000 years, we’ve created unprecedented conditions in a very short space of time. So the overarching threat to shark populations now is very different to what it would have been for thousands and thousands of years.

B

Yes well, we as humans are now geological powers, and we show this in so many ways. Here in this display we have what we are calling the fossils of the future – these are all basically species that have become established here over the past century as a result of human actions – for example something like racoons which are now quite common in Europe – I think they shoot about 100,000 a year and still they are abundant, it’s insane! Here we have razor clams – I think here they are one of the most dominant species in terms of biomass, but they have only really been here I think since about the 1980s – before that we had maybe six or seven native species in the North-East Atlantic but these have basically all been eradicated by this American species, which is somehow much more efficient. So we are a geological force and the palaeontologists of the far future, if there is a far future, they will have quite some trouble finding out specifics of our time – nothing’s going to be the way it was. We even have plastiglomerates now, like our signature in a rock. We’re actually starting to change the basic stratigraphy of the planet.

We have around 20,000 specimens here in the museum collected from the North Sea. A significant part of this collection is made up of terrestrial mammals but also marine mammals. We basically see a lot of North Sea fauna which is radiocarbon dated to about 8000, 7000 years ago and they contain for example bottlenose dolphin, some common species of seals, like a modern, very familiar North Sea really, but there are some differences for example the bottlenose dolphins are now quite rare but their fossils seem to be pretty abundant. If we go further back, we find Beluga, walrus, bearded seal or harp seal, and these are relatively difficult to interpret because – these arctic species, as a whole – this feels like a natural, modern assemblage from shallow arctic waters, but these mostly date to about 40,000 years old and this is weird. This is because 40,000 years ago, sea levels were at least 80 metres below levels today, therefore the North Sea was 40 metres above sea level… and so then you would see like, a walrus, 40 metres above sea level!

So, there are some ways to explain these sort of things away. One of them is that we these arctic marine mammals swim up-river, but this does seem, from Scotland to Norway all the way up-river, it seems a bit far. We also might think about whether these radiocarbon dates are reliable, and it may seem that they’re not. Maybe they are way too young. And it’s probably that younger carbon has infiltrated these bones, and of course we need all kinds of preparations to get a suitable, pure sample of bone collagen, but then if that has been altered on a microscopic scale by microbia, you may not be able to detect it and then your radiocarbon dating is way too young. It seems the most likely case that these walrus and beluga and stuff are about 100,000 to 80,000 years old. And that would fit with sea level reconstructions because then you are about 20, 30 metres above, while the climate has already deteriorated into a fairly cold ice age climate. Afterwards, you get dry land, and mammoths arrive, the saber-toothed cat which we have examples of here – this one is about 30,000 years old – and then from about 9000 years we see the submergence again of the North Sea area and you start finding common and more-or-less recent mammals.

M

That’s interesting – the returnal nature of these animal groups – they are familiar today but have this history of moving away from this part of the world then returning with fluctuating climate conditions – that capacity for migration and adaptation is quite impressive and something I have maybe overlooked.

B

Definitely impressive – and also the speed at which some of these species can actually migrate is impressive. For example, if you look at hippopotamus, it occurred here about 100,000 years ago in the Eemian, and possibly only for a couple of thousand years, and within that very short period they migrate from a refuge either quite far south of here, possibly even Africa. If not stopped by humans, many of these animals have great potential for keeping up with climate change. The thing is that if it is too fast then that’s the point they can’t keep up, and basically this zone in which they live, this climate zone which suits them, moves away and leaves them behind, and it sort of pinches out. And when that happens you have serious problems. Many plant ecologists are now fearing this now for some plant species.

M

Do you think that’s part of our psychology around animals and plants as well, that maybe the fact that animals have that great capacity for migration, that this takes a backseat in our imagination, maybe a hidden part of the narrative around the way in which environments change? This has really emphasised that bit for me that maybe I haven’t thought about as much, are those patterns of retreat and re-emergence – there are parallels here to memory.

B

Completely. And the terrestrial part is of course better known than the marine environment, it is more broken up. Of course, we know about and have here examples of woolly rhino, but also some of these smaller mammals that were there like voles, mice, and even their fossils are recovered from the beaches. The beaver as well is another species that fits very well in this Mesolithic period, in this sort of pine needle forest with lots of water, and it would also be hunted by humans.  

The problem here in the Netherlands is that one of the first areas where they have been reintroduced, maybe 15 years ago, it was like a great achievement, and now they are actually giving out permits where they say it’s okay to kill these beavers where they are really causing too much damage. I find it fascinating – and the same thing is going on as well now with the wolf here in the Netherlands – it is a European protected species, and when they were first being spotted, generally people were quite excited, except sometimes for farmers, but now it’s so common that this mentality is changing like ‘maybe we should do something about this’, and I would not be surprised I think if in 10 years permits will probably also be issued to kill these ‘problem’ wolves, like they might consider they are getting too close to humans or to livestock or whatever… it’s a very interesting way of us looking at animals and also looking at nature, because, especially in the Netherlands, everything in nature is sort of decided by humans. If you look at like, a natural reserve, like if you came down here by train you probably passed the Oostvaardersplassen. Well here for example everything may seem wild but it’s all decided by humans even the ground water table, so nature basically is human decision making, and human values, and we tend to value some things over others most of the time. A classic example is actually if you look at our Meadow Birch - especially here in South Holland – huge sums of money are being invested in protecting them, because they are declining globally, or at least we basically are strongholds of them, but then if you look at the measures that might be taken for example removing foxes, killing birds of prey – this sounds insane, I mean not that recently we considered birds of prey to be very rare. Apparently, we are deciding that the life of a fox is worth less.

M

How much do we know about bird species and populations in this Doggerland period?

B

What’s always difficult as we’ve discussed is dating these fossils for instance with radiocarbon dating. Many of these bird bones I have passed them on for analysis a couple of times and it didn’t work, I did not obtain any data. So with many of the bird bones we really do not know how old they are. What you have too with birds is, if you look at that range of any particular species, for example they might breed in the arctic and winter in the south of Spain, so you can’t easily say if you find a particular species, how this fits into an arctic climate. So that’s the difficult part. What we do find is that predominantly, most of the bird bones are from ducks or geese, and they do fit rather well with that Mesolithic Doggerland, large marsh-type area, and of course these may very well have been hunted by humans. I have personally not yet found any evidence of this though, like cut marks or something. With fish – the same story. We do find quite a lot of fish remains, but in many cases again we can’t pinpoint whether they are Holocene or Pleistocene. Most of the fish bone likely fits the Holocene, so the climate would be more temperate.