Watch and listen: The science of 2018 in audio and video

[Witness and family singing a traditional song about the baobab]

Interviewee: Witness Konzanayi

Growing up we would name the baobab trees after, you know, maybe after their shape. If it is too ugly, say ‘this ugly one’, if it produces a fruit or sweet foods, we’ll say this one is ‘sweet mama’.

Interviewee: Chris Surridge

The baobab is a completely unique tree in lots of respects, those sort of massive trees that are just about as wide as they are tall. It’s probably the oldest lived, it’s certainly the largest of the angiosperms, these flowering plants.

Interviewee: Witness Konzanayi

It is a tree that every child will identify with.

Interviewer: Noah Baker

If you picture an African savannah, more likely than not you’ll picture a baobab tree. A solemn giant, somehow bulbous and spindly at the same time, often described as growing upside-down. Now, new research investigating the age of baobabs has shown that many of the largest and oldest trees in the world are dead or dying, and scientists don’t know why.

Interviewee: Witness Konzanayi

Once upon a time, a long time ago, the Creator invited all animals to his office so that he could give them trees, you know seedlings for planting.

Interviewer: Noah Baker

That’s Witness Konzanayi from the University of Cape Town in South Africa. He’s just finished his PhD on the governance of the baobab.

Interviewee: Witness Konzanayi

And the hyena of all animals was very lazy and he went to the Creator very late, and when he got there the only seedling that was left was that of a baobab tree. And he didn’t impress the hyena, so in anger the hyena took the seedling, threw it far away. That’s what happened, that’s how the baobab ended up with such an ugly shape.

Interviewer: Noah Baker

There are countless folktales like this one, each surrounding the baobab, many explaining its bizarre shape. Here’s Chris Surridge, the editor of Nature Plants with the scientific version.

Interviewee: Chris Surridge

Normally, trees grow, they have a trunk, and they pretty much have one trunk and they split off further up into branches. Now baobabs are a bit weird in that they through their life can produce additional trunks that come up out of the ground. You sometimes see suckers come out of things like blackberries, but trees do not do this. But the baobab does, it throws up these extra trunks, a ring of stems which then fuse together to form this empty centre. They become sort of circular but with a gap in the middle.

Interviewer: Noah Baker

This is the leading theory for how baobabs have ended up so fat, and also explains why, more often than not, they have huge cavities inside. This bizarre architecture leads to problems if scientists want to find out how old a tree is.

Interviewee: Chris Surridge

Normally, when you try and date a tree you have to chop it down and count the rings into the centre, or you put a bore in and you can do that and check these. But there’s no centre to a baobab tree.

Interviewer: Noah Baker

So, when researchers decided to measure the age of the largest baobabs known across the African continent, they had to turn to another method. Here’s Adrian Patrut from the University of Babeş-Bolyai in Romania.

Interviewee: Adrian Patrut

The only possibility to date a baobab is actually to radiocarbon date samples collected from each stem.

Interviewer: Noah Baker

Radio carbon dating is not uncommon when dealing with very old trees. In fact, trees are often used to calibrate carbon dating methods – because counting tree rings is such a reliable way of measuring age, it can be used as a solid point of comparison. Adrian Patrut’s team started surveying trees in 2005, and some of those they surveyed were truly ancient.

Interviewee: Adrian Patrut

The oldest trees were around 2,000 years old, and we found a specimen in Zimbabwe, the so-called Panke baobab, and we collected samples which were up to 2,450 years old.

Interviewer: Noah Baker

These are trees which sprouted before Aristotle even proposed the division of the sciences. Trees which were already centuries old when Julius Caesar took the throne in Rome.

Interviewee: Chris Surridge

This is just an incredible age. Trees are happy to grow for hundreds of years, but getting up to these sorts of millennial ages is something that the flowering plants and flowering trees just don’t do.

Interviewer: Noah Baker

It’s worth noting here that there are non-flowering trees which are even older. Now, when a baobab gets really large or old, it can take on a particular significance. Here’s Witness again.

Interviewee: Witness Konzanayi

To an African person who identifies with these trees, once a tree becomes this big, it becomes sacred. They become more venues for spirits of the land.

Interviewer: Noah Baker

This significance adds even more weight to another discovery that Patrut and his team made.

Interviewee: Adrian Patrut

It was very unexpected to find that many old and large trees die in a very short timespan.

Interviewer: Noah Baker

Specifically, they found that 9 of the 13 oldest trees measured, and 5 of the 6 largest trees, have all died in the last 12 years. Now, these trees are all spread across Africa, sometimes thousands of miles apart. There was no sign of disease and the revered trees are usually very well cared for – they all even had names. It therefore seems too much of a coincidence that all of these deaths could happen by chance so suddenly. In fact, Patrut claims that it’s impossible.

Interviewee: Adrian Patrut

Scientifically it is impossible for trees which have an age limit of over 2,000 years to die in such a large number over a such short timespan.

Interviewer: Noah Baker

It begs the question then – what’s causing the deaths of these Baobabs?

Interviewee: Chris Surridge

The obvious conclusion is that it’s something environmental, something to do with changes in climate. But again, that’s very difficult to nail down because over 2,000 years these trees have seen a great deal of climate. I mean, they’ve lived through the Little Ice Ages that happened in about the 1400s, 1500s, so they’ve seen much colder temperatures than now. They’ve seen droughts, they’ve seen practically floods, and yet they have carried through that. It is true that as far as we can tell, the temperature in these areas is warmer now than it has often been in the past, and it is also quite dry at the moment so maybe this is going on. But we really don’t know what it is that is killing these trees, if indeed this is an unusual amount of deaths.

Interviewer: Noah Baker

It’s an interesting scientific mystery. As an academic who works with the baobab, Witness too was intrigued, but for him speaking as a Zimbabwean, the findings also represented something else.

Interviewee: Witness Konzanayi

To ecologists it is just the dying of trees, but to an African person the death of such big trees means the death of culture, it means the death of identity, it means the death of spirituality.

[Witness and family singing a traditional song about the baobab]

Interviewee: Witness Konzanayi

Increasingly I think people are getting to know about climate change, even in the modest areas, in fact you don’t need to be told – you live it because you see your leaves are drying, we experience floods every year. But what I’m not sure of is if people are able to relate the deaths of these trees to climate change. If the big trees are dying I think what we need to do is to quickly establish what the cause is, because for some communities, the baobab tree defines who they are.

[Witness and family singing a traditional song about the baobab]

Interviewer: Ellie Mackay

When it comes to doing scientific fieldwork, a tropical island like those in the Chagos Archipelago probably sounds like an ideal location. But as I heard this week, it’s not all margaritas on the beach.

Interviewee: Nick Graham

No, far from it. It’s hard work and you know it’s hot, it’s far from a holiday. I lost 3 kilos on the last trip I went on.

Interviewer: Ellie Mackay

This is Nick Graham, lead author of a new paper exploring some of the complex ecosystems on the Chagos Archipelago, a chain of coral atolls in the Indian Ocean. His team have been hard at work uncovering a fascinating but worrying chain of events that links the arrival of invasive rats with the health of coral reefs in the surrounding water, and it’s all thanks to poop. The Chagos is home to a huge number and density of seabirds which feed on nutrient-rich fish in the open ocean. When these seabirds come to roost, the nutrients in their droppings get washed on to the shallow reefs nearby so fish there grow bigger and faster. These fish then graze on the corals, preventing a build-up of algae which would otherwise slow the corals’ growth. But as with most tropical islands around the world, the vast majority of the islands in the Chagos Archipelago have been invaded by rats which have wiped out the unprepared bird populations. Without the birds, there’s no poop, and therefore less nitrogen runoff so fish are smaller and there’s less maintenance of the coral reef. So, introduce rats on the land and you harm the coral in the ocean. Nick Graham sent me an audio recording from one of the rat-free islands. And I gave him a call to ask him what it’s like standing on these islands.

[Audio recording of bird noises]

Interviewee: Nick Graham

When you step foot on one of the bird islands, the birds are very, very noisy, the skies are full of birds flying around overhead, the vegetation and the trees are full of birds so they’re roosting or sitting on nests. You know, it’s a really alive place. It’s a vibrant place full of frigatebirds, shearwaters, boobies, terns, noddies and the island’s smell - you can really smell the pungent guano, the bird poo, in the air.

Interviewer: Ellie Mackay

And what about the other islands, the rat-infested islands? You sent me some audio from there as well.

Interviewee: Nick Graham

It’s completely different. The skies are empty, the islands are quiet, there’s next to no seabirds on them, you don’t have the pungent smell in the air. It’s chalk and cheese - they’re completely different.

Interviewer: Ellie Mackay

And this difference is all down to the rats?

Interviewee: Nick Graham

That’s right. So, the islands with no rats on them have about 760 times more seabirds than the islands with rats. This is a huge difference.

Interviewer: Ellie Mackay

And so, to compare the two islands, you’ve measured lots of different factors: nitrogen levels in the leaves and soil, and in the tissue of fish and sponges and algae, you measured fish biomass and diversity, you sampled parrotfish bite marks to measure grazing rates and coral erosion. One strange thing I noticed that you looked at was damselfish ear bones - why was that?

Interviewee: Nick Graham

That’s right. So, the interesting thing with fish is that the ear bones in fish lay down growth rings, very much like a tree does. So, you can actually quite accurately age a fish by the rings that are laid down annually in their ear bones. These ear bones are called otoliths. So, we remove the otoliths from fish on islands with and without rats to look at their growth rates.

Interviewer: Ellie Mackay

And how fiddly a technique is that? How big are these ear bones and do you put them under a microscope to count the rings, or?

Interviewee: Nick Graham

That’s right. So, the otoliths are very small, maybe 4 or 5 millimetres wide. You have to fix them onto a glass tile and then very carefully grind the edge of the otolith flat, and then you can look at that smooth surface and count growth rings that way. And I think this is the first time that the influence of seabirds in terms of the nutrients they’re putting into the reefs have been shown to influence the growth rates of invertebrate.

Interviewer: Ellie Mackay

And the results you got from all of these measurements, the number are pretty big. The rat-free islands had 250 times more nitrogen, 50% higher biomass of fish, 3 times more grazing of the reef and 4 times more bioerosion of the reef. So, were you surprised to see this much difference between the rat-infested and the rat-free islands?

Interviewee: Nick Graham

This was a high-risk project. I didn’t know how the results were going to turn out. We were completely blown away by just how strong the signals are so it’s really amazing to see just how important these seabirds are for the coral reefs.

Interviewer: Ellie Mackay

And what are you hoping your research will be used for, because you’ve sort of put a call-to-action at the end of your paper?

Interviewee: Nick Graham

That’s right. I think the study really speaks quite clearly to the benefit of de-ratting tropical islands. We’re constantly trying to look at ways to bolster the health of coral reef ecosystems which are really at the frontline of impacts from climate change, and it’s very difficult to find tangible things we can do for reefs, but rat eradication I think should be a high priority for conservation and management efforts. We know it can be done, it’s not nearly as costly as a lot of other management interventions, and we know that it would have a huge benefit for terrestrial and marine ecosystems.

Interviewer: Adam Levy

For chemist Lee Cronin chemistry is all about discovery. And despite methods and techniques that have developed leaps and bounds over the centuries, for Lee the process of discovery is still all about the journey.

Interviewee: Lee Cronin

It’s very difficult when you ask a chemist in the lab to go discover something. It’s a bit like asking someone to go in a boat now and find a new continent. Something invariably goes wrong and more interesting happens, and then we follow that up, and I think that is the point where conventionally a lot of discoveries are made today.

Interviewer: Adam Levy

But despite his love of the voyage, Lee thinks it’s time to change up the process. Not the aspect that relies on some magical combination of luck and intuition, but exactly how the search is carried out. Lee wants to automate the quest for new reactions. Machines already exist to automate certain tasks in chemistry, but they tend to follow specific programming and recipes rather than searching for new discoveries. There have also been attempts to aid discovery with machine learning, where a computer is trained with data and learns how reactions might operate. Lee wanted to make a machine that could learn and carry out tasks. I called him up to find out more.

Interviewee: Lee Cronin

So, what we’ve tried to do is use machine learning to classify where the outcome of a reaction - that’s when you mix two chemicals together - whether something has happened or not, and then you can use that as a basis to then, you know, navigate round if you like your new chemical space or sail your yacht around your unknown islands and map them.

Interviewer: Adam Levy

And your machine isn’t just learning, it’s doing, it’s doing experiments.

Interviewee: Lee Cronin

Yeah, we do three crucially important things. Number one, we start with an empty database, except just it knows the ingredients that we have at our disposal. Number two, it just randomly selects the ingredients, the chemicals to add together so it has no bias. And number three, it does this in real time so it actually decides what to do and then mixes the chemicals together and watches what happens.

Interviewer: Adam Levy

When we say ‘it’ in these sentences, we’re actually talking about a robot. Can you describe what this robot is, because it’s not like some kind of humanoid thing sitting at a chemistry lab table, right?

Interviewee: Lee Cronin

No, but actually it does things very similar to what a humanoid would do or a human being would do at the chemistry lab table. A chemist would typically mix chemicals together in a round-bottom flask, put them on the stirrer and heat it up, and that is what this robot does. You plug the chemicals into the robot, and it moves those chemicals as liquids in a solvent to the reactor, and then the reaction happens and the robot automatically takes a sample and moves it to a detector. And it's basically like a human being using its eyes or your ears so it happens really quickly and seamlessly.

Interviewer: Adam Levy

So, is this really a closed system? Is this doing everything or is there still need for human input at some stage?

Interviewee: Lee Cronin

Oh yeah, the human’s crucial. This is not about replacing a human. So, what this robot does, it’s just a labour-saving tool. The robot is only as good as the chemist that’s trained it. Well, the robot would do the experiment and the chemist would tell the robot whether the outcome of the experiment was reactive or unreactive, so whether something happened or not. And so, the robot will then start to guess after a while and then the human will go yeah, you’re right, you’re right. And then there gets to a crucial point where it has done about 10% of the possible combinations, it is able to predict what will happen next and it just speeds up our ability to discover new reactions and new molecules. Human time is limited and so one of the things that the robot can do is basically do reactions the human doesn’t have time to do and would normally discard. It can do about 36 reactions a day, and a chemist would only typically do maybe 3 or 4 such reactions a day.

Interviewer: Adam Levy

We’ve described how the process works, but have you actually managed to find anything novel with this robot?

Interviewee: Lee Cronin

I’m pretty happy to say that I think I could convince maybe 9 out of 10 chemists that the robot had done some reactions where the outcome couldn’t be predicted beforehand, and that’s for me really exciting.

Interviewer: Adam Levy

Robots and automated machines are already used in chemistry, in industry. Just how different is the system that you’re using here from the kind of robots that might exist in other contexts in chemistry?

Interviewee: Lee Cronin

What’s different about our system is its integration and the fact it searches for reactivity. What we’re doing is actually quite unusual in that it basically is able to search without any target in mind, and then what we needed to make sure we were doing, not just having new sensors and not having targets, but actually having machine learning to actually correctly search those reagent or ingredient combinations.

Interviewer: Adam Levy

What actual applications will these differences be useful for?

Interviewee: Lee Cronin

Well, we’re really excited because we think in terms of discovery science, anything we need new molecules, so new drugs, new dyes, drug delivery systems, new materials. Now, there’s a problem when you’re discovering when you don’t know what you’re looking for. So, the next thing that we’re going to do is add another little sensor, but the sensor on to this will then have a desire and say right, we want to find, I don’t know, the bluest blue thing. So now, let’s not just look for new stuff but it has to be new and blue.

Interviewer: Adam Levy

And personally, what are you most excited about the opportunities that having this integrated robot system could open up?

Interviewee: Lee Cronin

Well, I’m hoping that what it will do is tell us more about the laws of chemistry, and allow us to discover molecules that we just wouldn’t have access to using our existing knowledge. I kind of liken it a bit like to writing poetry. Shakespeare was really interesting in writing poetry and verse because he invented new words. What I’m interested in this robot seeing it do, is able to invent new reactions. Then those reactions can be translated back to the normal chemistry language, and then the chemist is able to use those new reactions to make new molecules. For me that’s super exciting.

Interviewer: Lizzie Gibney

So first off, congratulations!

Interviewee: Donna Strickland

Thanks very much.

Interviewer: Lizzie Gibney

I understand that if we take you back to last Tuesday, the call from Stockholm was something of a surprise?

Interviewee: Donna Strickland

Of course, it was a total surprise, yes. And it was also 5 in the morning, so…

Interviewer: Lizzie Gibney

And the research that you won for was done in 1985, while you were a PhD student experimenting with lasers. What was it that you were trying to achieve at the time?

Interviewee: Donna Strickland

My PhD project was actually doing something that required a high-intensity laser. It was supposed to work in a way that many, many photons of light would interact with an atom all at the same time. And to do that you need to have all of your photons squeezed into small volume and that means you focus it with the lens down and you also squeeze in time. And so that’s what we were trying to do, but unfortunately, if you do that inside your laser it blows up. And so the idea came around to say okay, what we have to do is not squeeze all the pulses first, stretch them out so that it’s over a great big volume, amplify it up and then when we have all of the photons in the great big volume, you can squeeze it back down to a small volume, and now you have a really intense source of light.

Interviewer: Lizzie Gibney

And why is it that you wanted to improve the intensity of the lasers?

Interviewee: Donna Strickland

Well we wanted to interact with atoms in new ways and this type of laser can now have a force on an electron that’s bigger than the force that holds the electron to the atom. And also, it can be done very shortly and so the electrons simply fly off the atoms when they’re inside these laser fields.

Interviewer: Lizzie Gibney

So, if they’re a greater intensity that’s useful both in physics but also for applications including corrective laser eye surgery?

Interviewee: Donna Strickland

So, when people get this corrective surgery, people would actually scalpel off the outside part of the cornea, and then they would use the UV laser to reshape the cornea into new shape so that you could see and then put the flap back. What the ultrafast laser does is that because it doesn’t have to just cut from the surface, it’s only at the intense focal point that it does this damage where the electrons come off the atoms, you could actually put your laser and scan it over your cornea and it would cut underneath that. Instead of using a metal scalpel you can use a laser.

Interviewer: Lizzie Gibney

Sounds like a much less painful process.

Interviewee: Donna Strickland

That’s right, and it can be very precise with the laser.

Interviewer: Lizzie Gibney

Now, I wish we didn’t have to talk about gender. I’m sure that’s a topic that you’ve spoken about a lot this week, but as you’ll be very well aware, you know, you’re of course just the third woman to win a Nobel Prize in Physics. I guess first off, do you think that women are currently underrepresented among the Nobel laureates?

Interviewee: Donna Strickland

Well, 3 in 100 years or something – I think there are a higher percentage of women doing fantastic science than that, so probably we are underrepresented by the Nobel Prize, yes.

Interviewer: Lizzie Gibney

Lots of people have asked you about being a woman in physics, and I think that you said so far that you have always been treated fairly and paid well.

Interviewee: Donna Strickland

Actually, the University of Waterloo is always very careful. At one point, I got this letter, you know, saying that, “We look into making sure that women are paid equal but we realised…” And then a whole long line at the very end was, “And you were being treated equal so you won’t get a raise.” And I went well too bad because I would have liked the raise but at least I’m being treated equal! So that’s the way it is.

Interviewer: Lizzie Gibney

Well that’s really good to know. And much has also been made of the fact that you are an associate professor rather than a professor, and I think you’d said that you’d never applied, is that right?

Interviewee: Donna Strickland

Yeah, now I really wish I just had. I had colleagues that were saying, “Why aren’t you applying, you should be applying.” And I sort of just said, “Okay, I’ll probably do it next year.”

Interviewer: Lizzie Gibney

And to get a bit meta, obviously, you know I started these few questions by apologising for asking you about the very fact that you’re a woman. How has it felt over the past few days answering so many questions on that topic?

Interviewee: Donna Strickland

I do hope that we do get to the point, we all hope we get to the point where this just becomes not discussed anymore. I mean, so hopefully soon there’s enough women and enough people of colour and enough of every group out there that feels that they get the recognition they deserve, and then we don’t have to talk about it anymore.

Interviewer: Lizzie Gibney

Any suggestions on how we can reach that point, either what advice to younger scientists or even to the Nobels as to how to make the system work better?

Interviewee: Donna Strickland

I think we’ve been pushing for a lot of years and I do feel like women’s lib was talked about a lot in the 70s and I certainly always felt that, you know, as a woman, I could do whatever the heck I wanted. You know, and maybe a lot of women who felt that got out there and did it and maybe we let it slide again. Certainly, this is a moment in history where women around the world aren’t letting much slide anymore, so I think things are changing again, fairly quickly again. Question is whether we can consistently keep moving forward until it’s all done.

Interviewer: Lizzie Gibney

And Donna, you now have an incredible platform from which to speak, being a Nobel laureate. How do you plan to use that?

Interviewee: Donna Strickland

I don’t know! It’s kind of a scary kind of thing because I am somebody who just talks a lot without thinking and people have been quoting me back and I think did I actually say that? So that’s got me a little scared. I will have to practice not just saying the first thing that comes into my mind.

Interviewer: Lizzie Gibney

And how has your life changed since becoming a Nobel laureate on Tuesday?

Interviewee: Donna Strickland

Oh, completely! This is just completely crazy and you know, I got to talk to the Prime Minister of Canada for the first time ever and he was very nice about it because I said, “This is like your life all the time.” And he said, “No, I don’t always get to speak to a Nobel laureate.”

Interviewer: Lizzie Gibney

Wow, well enjoy it! It sounds like it’s hectic but congratulations again.

Interviewee: Donna Strickland

Thank you very much.