Podcast: Rats, reefs, and career streaks

This is a transcript of the 12^th July 2018 edition of the weekly Nature Podcast. Audio files for the current show and archive episodes can be accessed from the Nature Podcast index page (http://www.nature.com/nature/podcast), which also contains details on how to subscribe to the Nature Podcast for FREE, and has troubleshooting top-tips. Send us your feedback to podcast@nature.com.

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Host: Adam Levy

Welcome back to the Nature Podcast. This week: how careers are marked by successful streaks and the lessons from Cape Town’s water crisis.

Host: Shamini Bundell

Plus, the link between coral reefs and rats. I’m Shamini Bundell.

Host: Adam Levy

And I’m Adam Levy.

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Host: Adam Levy

Shamini, what would you say has been your biggest success?

Host: Shamini Bundell

Oh, well, there was the time that I got like a week’s worth of food for under a fiver in the reduced section at the supermarket.

Host: Adam Levy

I mean, that is very impressive but I did mean the biggest success of your professional career.

Host: Shamini Bundell

Oh, right. I don’t know, I don’t really have sort of peaks and troughs. I think I’m more of a sort of steady stream of brilliance type person.

Host: Adam Levy

It’s interesting that you think that of yourself but it’s just that in our next package, Noah Baker has been investigating career success, and a new paper suggests people's success tends to come in bursts. But maybe you’re the exception Shamini…

Host: Shamini Bundell

Ah, well, I mean I have always considered myself pretty exceptional but I might have to hear more about this research before I decide.

Host: Adam Levy

Well, let’s hand over to Noah.

Interviewer: Noah Baker

Think back to 1905: Teddy Roosevelt is sworn in for his second term as US president, Henri Matisse leads the first fauvist exhibition in Paris and over in Switzerland, Einstein is about to do something quite special.

Interviewee: Dashun Wang

Albert Einstein at the age of 26 published several discoveries that changed physics forever.

Interviewer: Noah Baker

This is Dashun Wang from Northwestern University in the States.

Interviewee: Dashun Wang

By the summer of that year, he had explained Brownian motion, discovered photoelectric effect for which he won the Nobel Prize, and developed the theory of special relativity. And before the year ended, he wrote down the most famous equation on Earth which is E = mc².

Interviewer: Noah Baker

Dashun describes this string of success as a ‘hot streak’. In a Nature paper this week, Dashun investigates the hot streak phenomenon, asking how they might shape career success. But before we get to that, a bit of background on studying success.

Interviewee: Dashun Wang

Recently my group has been very focused on this emerging area called science of science, which is a quest to turn the scientific mythos on curiosities on ourselves.

Interviewer: Noah Baker

This kind of research is fairly new. Here’s Phil Ball, a science writer with a particular interest in the science of success.

Interviewee: Phil Ball

The idea that we can use science to understand human behaviour has really only come about in the last maybe couple of decades, in a serious way. And a big part of the reason for that is that we have now have access to huge amounts of data that has allowed people to start looking generally statistically, at what humans do to try to look for signs of regularities, of statistical regularities. Just in the same way as there are statistical regularities in the way molecules behave.

Interviewer: Noah Baker

But in his past work looking at scientific careers, Dashun has found anything but regularity.

Interviewee: Dashun Wang

In my earlier co-authored work, we found that for a scientific career the biggest hit in the career actually occurs randomly in the career. So, it could be in other words, it could be within equal probability to be the very first work of your career or very last work of your career, or somewhere in the middle. And we find over and over that what we call the random impact rule is very robust. But it actually raises a deep puzzle for me because it makes me start wondering, then what happens if we finally produce a breakthrough, right? Because on the other hand, we also tend to think you know winnings should beget more winnings.

Interviewer: Noah Baker

This conflict between anecdotal evidence like Einstein’s hot streak and the statistical suggestion that success is random posed a puzzle for Dashun. To pick apart the problem, he delved into the careers of thousands of artists, film directors and scientists. Dashun’s first job was to find suitable metrics to quantify success - tricky for three such different disciplines.

Interviewee: Dashun Wang

That’s the first question, right, because success depends on so many different dimensions. By definition, any quantity to measure we have, only imperfectly captures one of the many dimensions that we can use to quantify success.

Interviewer: Noah Baker

After much searching and consulting previous work, the metrics Dashun settled on as a proxy for success were: for scientists - number of citations, for artists - price at auction, and for film directors - IMDB ratings. Sure enough, Dashun found that the success of any given piece of work in a person’s career appears to be random, but when he looked deeper he found something else.

Interviewee: Dashun Wang

Although each hit within a career occurs randomly, the relative timing, however, follows very predictable patterns. So, in fact these two schools of thought, these two seemingly contradicting points of view actually can be unified together by a hot streak phenomena.

Interviewer: Noah Baker

Dashun explained how this kind of phenomena works statistically.

Interviewee: Dashun Wang

And as you progress along your career, all of a sudden you reach a certain point that you are elevated to another level. It’s like you are not yourself anymore, and then you start to publish the work that’s full of fundamentally different distribution than what we saw you did otherwise. It lasts for about a short period of time, then you fall back to where you were.

Interviewer: Noah Baker

The model seems to fit well across careers of film directors, scientists and artists. And that suggests that the hot streak phenomenon is associated not with individual career types, but with people more broadly. To Phil Ball, it reminded him of another phenomenon.

Interviewee: Phil Ball

The immediate thing that that said to me is that one of the patterns that has been seen in other kinds of human behaviour is called ‘burstiness’ and it’s precisely this: that we do things in bursts. So, for example when we do our emails, we don’t sort of, you know, send them randomly through the day, we have little bursts. So, it seems that this sort of pattern in various ways is a characteristic of the way people organise their lives, organise their behaviour.

Interviewer: Noah Baker

It seems that many people have one hot streak in their career, and a few have two. In very rare cases people may have three. But what causes them? Well despite their efforts, Dashun and his team couldn’t come up with an answer.

Interviewee: Dashun Wang

We find although the hot streaks seem universal in the domains we studied, we don’t yet know actually why it happens and what triggers it.

Interviewer: Noah Baker

Dashun hopes that with more work, they’ll be able to start predicting when a hot streak may happen or how long it will last. But as of yet, it’s unclear if that’s a goal that can ever be achieved. Here’s Phil Ball again.

Interviewee: Phil Ball

It will be interesting to see whether any sort of predictive capacity comes out of this, and whether I mean, I think another thing that occurs to me, and it’s something that we’ve certainly seen in efforts to try to understand earthquakes, whether there are any kind of precursors that are detectable, whether you can tell that you’re just on the verge of having a hot streak appear. But it will be very interesting if looking at correlations there as physicists do, you could see that you’re starting to approach your hot streak. That will be very interesting.

Host: Adam Levy

That was London-based science writer Phil Ball, and before him you heard from Dashun Wang from Northwestern University in the States. You can read Dashun’s paper, plus a Nature editorial over at nature.com/nature. And if you want to hear more about his previous work, we have a video about it on our YouTube channel. Just search YouTube for ‘Is a scientific career predictable?’.

Host: Shamini Bundell

Now, we all love a good beach holiday, don’t we Adam?

Host: Adam Levy

Yeah, we certainly do.

Host: Shamini Bundell

Thailand, Fiji, the Maldives… where would you pick?

Host: Adam Levy

I’d probably go for the Chagos Archipelago.

Host: Shamini Bundell

Where?

Host: Adam Levy

The Chagos Archipelago. It’s the location of a paper published this week, all about how rats impact coral reefs.

Host: Shamini Bundell

Oh. Wait, how could rats affect coral reefs?

Host: Adam Levy

That is an excellent question and here’s Ellie Mackay to tell us more.

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.

Host: Shamini Bundell

That was Nick Graham from Lancaster University in the UK. We also have a video breaking down the link between rats and reefs. Watch that over on our YouTube channel: youtube.com/NatureVideoChannel.

Host: Adam Levy

Still to come later in the show, Britain is on course to exit the EU in a matter of months, and science organisations are arguing there’s an urgent need for immigration reform. Hear all about that in the News Chat, but now it’s time for our top stories from elsewhere. It’s the Research Highlights brought to you by Noah Baker.

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Interviewer: Noah Baker

After a long day in the lab, you might fancy putting on a virtual reality headset and immersing yourself in an interactive video game. But if your day job is studying molecular dynamics, well you might want to bring that VR kit into the lab. Researchers have been exploring whether off-the-shelf VR headsets and controllers could be useful for studying and manipulating 3D molecular structures. They created an interactive simulation and asked people to complete tasks such as threading methane through a carbon nanotube or tying a knot in a protein. Using virtual reality proved a more efficient and intuitive way of exploring the model molecules, even more so than a touchscreen tablet or a computer and a mouse. Read more on that in Science Advances.

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Interviewer: Noah Baker

3D printing can be used to make all kinds of different shapes and objects using all kinds of different materials. Now, researchers have devised a way to 3D print objects with both soft and rigid parts. They use photochromic resins that can be exposed to light to alter their flexibility. This means that certain sections of an object could be hard and rigid while other parts are soft and flexible. A tiny resin butterfly, for example, could be printed with a rigid body and wings but flexible joints between them, without the need to print any actual moving parts. Find more in Advanced Materials.

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Host: Shamini Bundell

Earlier this year, a catastrophic water shortage in Cape Town was in the news. You’ll probably remember seeing images of Capetonians queuing at municipal taps, and there was much talk of Day Zero - the day the authorities might have to shut the taps off as the water run out. Three successive years of drought - the worst the area had seen in more than a century - had severely depleted reservoirs. By the end of 2017, as the peak of summer arrived in Cape Town, water levels were frighteningly low. City authorities fined citizens for using too much water, and blamed climate change for the water shortage. But Professor Mike Muller from Wits University says that this is not fair. According to Muller, the hydrology models all predicted what was coming, and it was poor planning on the part of city authorities that was to blame for the water shortage. Climate change or not, says Muller, the crisis could have been averted if scientists’ warnings had been heeded. Our reporter Lorna Stewart gave him a call at his Johannesburg office.

Interviewee: Mike Muller

The models had certainly said to Cape Town that by 2015 they really should have increased their water supply capacity because they were reaching the limits of what could reliably be supplied. So, the hydrology and the modelling did wave a red flag, but for a variety of reasons the officials concerned decided that, I would say, to take a risk and it’s always pretty risky to gamble against nature. Nature’s got a very perverse sense of humour.

Interviewer: Lorna Stewart

What would you expect them to be doing to increase supply? It sounds like if the rains don’t come, the rains don’t come. Some water supply problems in the city are inevitable if there’s no rain.

Interviewee: Mike Muller

Well, speaking as a practitioner, what we do is in a case where there’s variable rainfall and we’re not sure, for instance, how we’re going to supply during the dry season, we will build a dam, we will build storage and we will make sure there’s enough water in storage to see us through the dry period. So, a lot of this is about estimating how long the dry period will last, and making sure that there is an ability to supply during that dry period.

Interviewer: Lorna Stewart

It’s a difficult balance, isn’t it, because this is a drought so severe that it would usually be only expected well, I’ve seen several different numbers, but certainly a very unusual event. Do you really think the government should be expected to fund large, expensive infrastructure projects for something which might not happen?

Interviewee: Mike Muller

I think, you know, that’s precisely the argument that the Cape Town City Council used. They’ve now been able to see what happens when you take that kind of risk.

Interviewer: Lorna Stewart

The model seems to have done, then, a good job of predicting what was to come to pass. But as the climate becomes more erratic and unpredictable, how well are existing models going to work there?

Interviewee: Mike Muller

You know, I mean this is an interesting technical problem which is about how do you capture non-stationarity, i.e. changing conditions in a model which you use with fixed data. And the answer is that you keep updating the data.

Interviewer: Lorna Stewart

Even if climate change didn’t cause this, could it have still played a role?

Interviewee: Mike Muller

There’s a lot of predictions about rainfall under climate change and suggestions that there are going to be more droughts rather than less droughts, and more floods rather than less floods, and more extreme floods rather than less extreme floods. Certainly for the Western Cape part of South Africa, the models do show that there will probably be less rainfall in the future than at present. We’re not seeing that trend very strongly yet, certainly I don’t know too many people who would say it is definitely happening, but the models are certainly very insistent, and these are the climate models, the climate models are very insistent that there will likely be less rainfall in the future. And that’s one of the things that has to be taken into account in planning. If we can manage today’s climate variability, and we have a very variable climate, we will probably be able to manage tomorrow’s climate change quite effectively.

Interviewer: Lorna Stewart

So, what are the lessons to be learnt from Cape Town? What does Cape Town and what do other cities need to do to prevent another similar or even worse water shortage in the future?

Interviewee: Mike Muller

On the technical side, we’re in the happy position in South Africa of actually having a very good modelling system if people would take notice of it, which puts hydrology and supply options and demand projections together and makes recommendations about what’s necessary. But what we’re finding is that human behaviour, encouraging people to use less water, regulating how they use water, is actually almost as difficult as predicting hydrology in variable climates. People call it the soft side of the business. It’s actually a much harder part of, in terms of how hard it is to make it happen, we’ve got to do the hard work of making sure we can predict and influence how people behave, because in the end people’s behaviour actually has a very large influence on the systems that we’re trying to manage.

Interviewer: Lorna Stewart

There does need to be something of a longer view in all of this, doesn’t there? I mean, some of the measures that I read about being taken to deal with the water shortage - buying bottled water, using disposable plates, cups, cutlery to save on washing up water, running dehumidifiers to sort of extract water from the air - they all make sense in water terms perhaps, but they’re going to drive climate change. They’re all energy-intensive, aren’t they?

Interviewee: Mike Muller

And that’s one of the reasons one doesn’t want to see people running into emergency responses, which tend to do things which perhaps in the long term are fully inexpensive. What the crisis has triggered is a lot now of the sensible responses that by the way were proposed almost ten years ago. And it’s a little sad to see this but I think it’s human nature, you know, we hope to avoid the worst and when it happens we scramble to catch up, and that is unfortunately in many urban areas the way that we address these long-term challenges. It becomes very inefficient for societies. You do damage to the infrastructure because it’s getting abused during these kind of shortage periods. It’s not good for economic activity - some of our farmers have had to sort of dig up vines and orchards. The tourist trade will take a year or two to pick up again, and it would be better for everyone concerned to do the right thing at the right time.

Host: Shamini Bundell

That was Mike Muller talking to our reporter Lorna Stewart. The Cape Town dams are twice as full today as they were this time last year, so the situation looks a lot better than it did a year ago. Although of course, no one is relaxing until they are full. Give Mike’s Comment piece a read over at nature.com/news.

Interviewer: Adam Levy

Finally this week, it’s time for the News Chat and reporter Lizzie Gibney joins us in the studio. Hi Lizzie.

Interviewee: Lizzie Gibney

Hi Adam.

Interviewer: Adam Levy

Now on the 29th March in 2019, the UK will, at least in theory, be leaving the European Union. Now, this is an issue for a huge number of things, but why could it be a somewhat big issue for research?

Interviewee: Lizzie Gibney

Well research generally in Europe is extremely collaborative, and crucially there are researchers, there are scientists who cross these borders at the moment, completely freely. And there’s a huge amount of concern that that will not potentially remain once the UK leaves the EU.

Interviewer: Adam Levy

And what are the scales we’re talking about here? What are the numbers of researchers crossing into the UK?

Interviewee: Lizzie Gibney

Well, this is something that is surprisingly hard to pin down. So, essentially it seems like through the various different routes there are at least around 20,000 researchers from outside Europe who come to the UK. And we also then tried to look at the number who come from Europe at the moment. Now, because there’s this free movement currently, that means that actually there aren’t official, reliable figures on these numbers. So, we’ve had to draw on some data from, for instance, the Higher Education Statistics Agency to figure out new starters in UK universities who come from European nations, and also to make some estimates. And it seems like overall, there may be perhaps tens of thousands more researchers who will need to somehow pass through the visa system once European researchers are included within that post-Brexit.

Interviewer: Adam Levy

What are the proposals to fix this situation after the UK is not in the European Union?

Interviewee: Lizzie Gibney

Well what most people want is to reform the system as a whole so it gets better for any highly-skilled worker to come to the UK, whether they’re from Europe or from the rest of the world. And making the system just quicker and cheaper, because at the moment in can cost quite something like £16,000 for a researcher to come with their family to the UK. Now, that’s an enormous amount and that’s way more than it costs in most other countries - it might be a couple of hundred dollars if you’re going to Canada, for instance. So, there are lots of reforms that could be made that would be very useful for everybody. But on top of that, there’s this worry that well, is it actually going to be at all possible? You know, Brexit is coming at us like a steam train and whilst there’s a transition period between the end of March 2019 which is technically it’s cut off point, and then the end of 2020 and there are some interim measures then, but this should all apply from 2021 and that’s not a long time given how much else the government is going to need to do in that period. So, there’s a lot of concern that if we don’t get some special measures in place for European researchers to kick in immediately at that point, there might be a big stymying of the flow that at the moment is so crucial to UK and European research.

Interviewer: Adam Levy

This isn’t the only thing that remains to be sorted out regarding Brexit. It’s coming at us on 29th March 2019 and we’ve just had the resignation of the Brexit Secretary, the Foreign Secretary of the country - there’s a lot that needs to be done. I’m not sure that this is going to be at the top of the government’s priority list.

Interviewee: Lizzie Gibney

Well, that’s right. Immigration is something that they've only committed to saying they will publish their proposals on after September. So, we’ve already got a few months to wait, and you know, that’s bringing it quite close up to the line of the end of this period of negotiation. We had a line in our story saying that the UK cabinet - that’s the senior decision-making body, senior ministers - are split on whether citizens from the EU should have any special privilege in terms of coming to the UK after Brexit, and I think that is perhaps playing it down slightly to say that they’re split, given that we now know the senior ministers are completely divided to the extent that they are quitting in their droves. We’re totally aware that there are still huge amounts of uncertainty, which is unfortunately a tagline I feel we have to attach to any Brexit story.

Interviewer: Adam Levy

But we’re scientists, we need to embrace uncertainty and accept it as part of our storytelling.

Interviewee: Lizzie Gibney

We do indeed.

Interviewer: Adam Levy

Well, from lows of Brexit to the highs, or potentially not highs, of a new drug just approved from the US Food and Drug Agency that is based on cannabis. What’s this drug aiming to do?

Interviewee: Lizzie Gibney

That’s right. So, the drug is called Epidiolex and it’s a treatment for epileptic seizures, and it’s based on cannabis compounds called cannabidiol. So yes, the FDA has just approved it and this means that the US Drug Enforcement Administration in the States has to somehow reclassify that drug so that it then becomes legal for doctors to actually prescribe it.

Interviewer: Adam Levy

But is medical marijuana not already legal in many states across America?

Interviewee: Lizzie Gibney

It is, it’s legal in 30 states as well as the District of Columbia, but it’s not legal federally, and this means that the way that it’s classed means that researchers have to jump through an enormous number of hoops to actually do any research with it at the moment.

Interviewer: Adam Levy

So, what would actually be the hoops required to manufacture a drug like this?

Interviewee: Lizzie Gibney

Because the drug is still consigned to this very restricted category under federal law, that means that you have to go through, you have to spend a lot of time and money to comply with that law, because what you’re handling is effectively an illicit substance. Then there’s also the problem of how you actually get enough of it to do research. So, there is only one lab that is certified to actually provide other labs with cannabis and its extracts and that’s at the University of Mississippi.

Interviewer: Adam Levy

So, what the US Food and Drug Agency are looking at is this drug for epilepsy, but what other research is underway using compounds from cannabis?

Interviewee: Lizzie Gibney

Well, aside from this treatment for epileptic seizures, there’s also a potential in terms of pain relief. So, one study from Columbia University looked at people who both smoked marijuana and took a much smaller dose of an opioid, and that they got the same pain relief as people who took a full opioid dose. And of course, there’s a bit of a crisis at the moment in terms of opioid addiction, for instance, in the States, and so there might be potential there to prescribe lower opioid doses. So that’s just one example.

Interviewer: Adam Levy

It’s important to note though that the US Food and Drug Agency is potentially just approving this particular drug. It’s not necessarily approving cannabis-based drugs in general.

Interviewee: Lizzie Gibney

That’s right, and if that happens then researchers in the States might not be able to ramp up the research in the way that they’d like to. It’s actually going to be legal in Canada to consume marijuana - both medically and recreationally - as of the 17th October, and Canada already has a lot of biotech firms who are coming up with innovative ways of making cannabinoids, including some of those which are much rarer and harder to create by genetically engineering them and growing them in yeast, for instance. So, there’s a lot of potential for boom there in Canada that the US might not be able to exploit.

Interviewer: Adam Levy

Lizzie, thank you for joining us. For more on both those stories head over to nature.com/news.

Host: Shamini Bundell

That’s it for this week, but don’t forget to check out our video explaining those ratty reefs over on our YouTube channel. And tune in to next week’s show to hear about a scientist who has a very mechanical way of working. I’m Shamini Bundell.

Interviewer: Adam Levy

And I’m Adam Levy. Thanks for listening.

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