Gardens, Plants and Climate Change

How can gardeners garden sustainably as climate conditions change?
25 August 2020
Presented by Chris Smith, Eva Higginbotham
Production by Katie Haylor.


photo of a rose


This week, with our climate changing, will the traditional “English country garden” become a thing of the past? Will pests and diseases surge? And how will flowers and food crops, and the pollinators that make them productive, be affected? Plus, news of how dust and dandruff can spread flu and other viruses. The chemical fingerprint that COVID-19 leaves on the body; and self-driving cars look set to take to the road...

In this episode

A graphic showing a face mid-cough and some virus particles.

01:04 - Flu spreading on dandruff

Scientists have been looking at how viruses can spread...

Flu spreading on dandruff
Nicole Bouvier, Icahn School of Medicine

Across the world, Covid-19 is making a comeback. Boris Johnson’s dubbed it a “second wave”, and the WHO have suggested that “people dropping their guard”, together with a relaxation of public health measures in many countries, is translating into a surge in cases. France is seeing nearly 4000 daily cases, and across Europe as a whole the total is close to 26,000 people testing positive each day. As a result people are trying to learn as much as possible about the manner in which coronaviruses - and other respiratory infections - spread. A lot of emphasis has been placed on respiratory droplets - blobs of moisture that come out of the airways when we breathe and talk, and can contain virus particles - and people are wearing face coverings and washing their hands to ward off the risk. But at Icahn School of Medicine at Mount Sinai, New York, Nicole Bouvier has been testing how flu spreads among guinea pigs. She’s found that respiratory droplets are indeed important, but that viruses can cling to other things, which may be even more numerous, as well…

Nicole - When humans breathe, or talk, or cough, or sneeze, there's all kinds of microscopic particles that come out of your respiratory tract; droplets of pure water, proteins, bits and pieces of dead cells, most of which is invisible. So we don't really think about it, but it's there. So presumably, guinea pigs were doing the same thing, and we wanted to know what exactly is coming out of them when they are infected with flu and putting flu out into the air.

Chris - How did you do the experiments?

Nicole - We put the guinea pigs in a special cage that had a fine air filter that prevents stuff from the environment coming in. And then we had the other side of the cage hooked up to an aerodynamic particle sizer, or an APS, and that's basically just a machine that can, not only count microscopic particles, but can tell you how big they are. And what we were finding is that there were just thousands of particles per second. Every time the guinea pig moved, there was this big poof of particles that were being detected. It suggested to us that actually the particles coming out of the cage were associated with movement. And that's when we started thinking, well, maybe this isn't just what's coming out of the respiratory tract, but it's just dust.

Chris - So these are guinea pigs with dandruff? Is that basically what you're saying?

Nicole - Yeah. You know, they are dandruffy animals, but so are we, I mean, humans slough millions of skin cells off every day.

Chris - But flu viruses don't grow in the skin. They grow in the nose and throat. So why is this dander and other particulate matter that's coming off the guinea pigs relevant?

Nicole - So what we did is, we took a guinea pig, and we infected it with influenza virus. And then we put the guinea pigs in a cage, and we sampled virus from the cage and from the animal's body, we just took a cotton swab and dipped it in some saline, and swabbed the animal's ears, and their paws, and their fur, and the sides of the cage. And we were able to actually grow a lot of viable flu virus from these swaps. And that indicated to us that the virus was actually being spread all over itself and its environment. And it kind of makes sense when you think about what guinea pigs are doing all day long, which is grooming themselves, and snuffling around, it makes sense that virus from their noses could be getting all over the place.

Chris - Does that mean then, that because there's virus on things other than droplets coming out of the nose and throat, that that could be infectious too?

Nicole - Exactly. We also did some measurements where we were trying to measure exactly what was coming out of just the guinea pigs respiratory tract. And what we found was that the amount of particles coming out of their respiratory tract, was just orders of magnitude smaller than what was coming out of the cage when it was awake and moving around. And so it seemed reasonable to think that maybe some of these particles from the environment, that if they were contaminated with flu virus, might actually be transporting the virus through the air, to the susceptible guinea pig next door.

Chris - Could you infect other animals? If you take those particles, can you demonstrate that there is viable virus, they're capable of infecting an uninfected individual?

Nicole - Yeah. So what we did is we took some virus and just painted it onto their fur. And then we put this animal into the cage next to a susceptible animal, and we were able to see transmission to the susceptible animal. And that suggests that particles that were conveying the virus, were actually not coming from the respiratory tract, because there was actually no virus replicating in the donor animal's respiratory tract at that point.

Chris - Do you think this is relevant to humans, then?

Nicole - It's entirely possible. You know, you could imagine a person who's sick in bed with the flu, if their bedsheets or their pillowcase gets contaminated. And then, you know, the nurse or their partner comes in the next morning, and flaps the sheet to straighten it out, that possibly viable flu virus could be aerosolised into the air in that way. And there was actually a really interesting experiment done in the 1940s where somebody intentionally contaminated a blanket with influenza virus, shook it in a closed container, and was able to sample a live virus from the air. So, you know, we know that this is possible to do. It's just something we haven't really thought about in many decades.

Chris - The obvious question is that the new coronavirus that we're all enthralled to at the moment is about the same size as flu. It's a respiratory infection. So do you think what you're finding for flu could be considered relevant to the coronavirus as well?

Nicole - Certainly, it's not out of the question to think it could be relevant. I think there are a couple of clues that we've seen in some of the COVID research so far. For instance, there was a study done in China where scientists did air sampling in various areas of a few hospitals. What they found is that the highest levels of airborne virus that they could detect, was in a room where healthcare workers were taking off their PPE. And that suggested to the authors that contaminated gowns, or bonnets, or gloves, in the process of being taken off could be shaken or rubbed in such a way that it was releasing coronavirus into the air. I think what we need to do is a little bit more research on what the mechanisms are by which the virus gets into the air. I think a lot of us just assume that it's coming out of the respiratory tract directly, with coughing, and sneezing, and breathing, and talking. But there may be other mechanisms at play that we need to consider and systematically study.

Doctor with blood samples

07:56 - Covid's metabolic signature

Scientists in Australia have been looking at Covid-19's metabolic signature...

Covid's metabolic signature
Jeremy Nicholson, Australian National Phenome Centre

As we reported here on the Naked Scientists a couple of weeks ago, COVID-19 is a confusing illness - some doctors are dubbing it the weirdest disease they’ve ever treated. What makes it weird is the broad range of severity: some don’t even know they’ve been infected, while among others it can be lethal. Significant numbers of people are also reporting long term symptoms, including fatigue, sensations of pins and needles, and sometimes struggling to think clearly.So what’s causing this? Scientists think that the disease may be producing long term changes in a range of organs, possibly because of damage to those organs during the initial illness. Recently, researchers at Cambridge University sent samples from Covid-19 patients here to the Australian National Phenome Centre at Murdoch University in Perth. There, using very sensitive chemical techniques, they’ve been able to spot changes in a range of substances in the bloodstreams of these patients. These signature changes appear to be very specific for coronavirus infection, so they can be used as an accurate test for the disorder. They also provide insights into why people are developing some of the symptoms they are, and, in the future, may enable us to predict who is most at risk. Phil Sansom heard how from Jeremy Nicholson, who’s leading the study...

Jeremy - There is a very marked signature, in fact it's surprisingly strong. So what we see, is a pattern that's related to liver dysfunction, to diabetes, to potential cardiovascular damage and cardiac risk. The thing that makes it unique, is it has a multiple system failure signature, which means that it stands out like a sore thumb. We've never seen anything quite like it

Phil - Is this specifically for people who get really severe COVID?

Jeremy - It looks as though it's largely independent of the degree of respiratory symptoms, which is potentially quite surprising. But if you think about it, you know, there's been reports now of people having brain damage, strokes, heart failure, gut effects, kidney effects. And what we're seeing is the combination of pretty much everything that everybody's been talking about for the last couple of months.

Phil - How easy is that to detect for you?

Jeremy - We have various different types of advanced chemical equipment, and it's all based on spectroscopy, the study of the chemical signatures of molecules. Molecules can absorb energy, and radiate energy in lots of different ways. They can also have characteristic mass profiles, and it doesn't matter which one we use. There's always a signature for COVID-19.

Phil - In terms of this sort of being almost a test for who's been infected, how does it compare to the other tests in terms of how quick it is, how easy it is?

Jeremy - When we started the work back in February, I wasn't terribly interested in detection per se, because I made an assumption that the PCR methods for testing for the virus were extremely good. And it turns out there's a huge number of the tests that have very large numbers of false negatives, which of course is a bad thing for a test. And we're using NMR spectroscopy, we have a test that is 100% sensitive, that works in four minutes, costing about 15 pounds or something like that. And that is gender independent, age independent. It's also independent of severity.

Phil - You know, everyone talks about how strange this virus is, and how strange this disease is. And it's strange that the one constant, is how universally disruptive this is to people's bodies.

Jeremy - Yeah. There are probably a number of reasons for that. The most important one is this is a disease that attacks epithelial cells, cells that line or cover surfaces. So the lung has a double epithelium. It has the cells that face the air, and it also has the blood vessels, which are very, very close indeed. But the whole of the body is full of blood vessels. And there's lots of reports in the literature about blocking tiny blood vessels, and also major blood vessel blockages as well. And that means any organ in the body, technically can be affected by COVID.

Phil - Jeremy, when can we expect to be able to take your test?

Jeremy - Well, you can take the test in our laboratory tomorrow, but this is informally. The pathway to getting it to a test that could really work and be deployed at scale is not necessarily a long one. It might only be eight to 12 weeks in an ideal situation.

Phil - And I've been talking to lots of people who are still sick, after months and months and months. Does this discovery that you made give them any insight?

Jeremy - Well, that's an interesting question. So, at the moment we don't know enough about it. What we do know is in some people that we've looked at, we've looked at them several months after they've actually had an episode, and they're still mapping with the COVID positives who were in the hospital. When we monitor people, we'll be able to assess quantitatively, whether they are going back to normal. At the moment, we can't accelerate people going back to normal. But what we will be able to do, is to have a better way of assessing the health of people who've had COVID, in a long-term followup.

 a photo of lips

14:12 - Editing out herpes

Scientists have come up with a gene editing tool for the Herpes Simplex virus...

Editing out herpes
Keith Jerome, Fred Hutchinson Cancer Research Center

Nearly two thirds of us are infected with the herpes simplex virus, which causes cold sores, genital herpes and occasionally even brain infections. The virus is a headache to treat because the infection is lifelong. This is because the virus hides, existing just as a piece of DNA, inside nerve cells. It periodically re-awakens to produce painful, infectious skin blisters. And although there are drugs that can control these flare ups when they happen, they can’t remove the viral DNA, so the problem keeps recurring. Now, researchers in the US have developed a pair of selective molecular scissors that can track down the rogue viral DNA inside nerve cells and cut it up, destroying the virus so - at least in experimental mice - it can’t come back. Chris Smith spoke to Keith Jerome...

Keith - Herpes is really sneaky, in that it actually establishes a form of itself that essentially goes into cells and then falls asleep. And that virus lives in the neurons, the nerve cells in your body. And then it can come back once a year, once a month, once a week, and cause lesions and ulcers and anything else, and all those drugs we have don't do anything about that sleeping form of the virus.

Chris - So it's effectively under the immune radar then? All the time it's dormant inside cells like that, the immune system can't see it. So it just gets ignored.

Keith - That's exactly right. The immune system controls it once it wakes up and starts making more copies of itself, and they take care of those new copies, but even the immune system doesn't do anything about that long-term sleeping form of the virus.

Chris - So what can you do about it?

Keith - Well, we've been using this really cool technology, that's been around for a little over a decade now called gene editing. This virus is made of DNA just like our body is. And that sleeping form is a little tiny circle of this DNA that lives in the nerve cells. And what gene editing allows us to do is basically use what I think of as molecular scissors, that can go into a cell and they can look through all the DNA in that cell and look for a very specific little stretch of the letters. And if they find those letters, they make a little cut. And so what we do is design very special scissors that ignore all of our own DNA, all the human DNA, but they look really hard for herpes. And if they find it, they make two little cuts, and so it basically falls apart and makes it go away.

Chris - And this works does it? You can actually demonstrate that you chop up the virus, and it then can no longer come back?

Keith - Yeah, exactly. So the study that we did was in mice. Mice get this sleeping form of herpes, just like we do. And then we can go in and we use something we call a vector. It's a different virus that carries these scissors to those same neurons. And when it does that, it starts cutting up the virus. And then we can measure after our therapy, how much of that sleeping form is actually left in the mice, after we've treated. And what we saw is we eliminated well over 90% of that virus. And if we could translate that into human beings, it's likely to prevent lesions, and ulcers, and disease, and transmission to other people, and all the things that we worry about.

Chris - How did you get the virus that was the Trojan horse that carried in the molecular scissors? How did you get that into the nerve cells in these animals?

Keith - Well, that was a really important part of our study, understanding the best way to get the scissors where they need to be. And we use another virus, it's called adeno-associated virus. We actually almost all have it, never causes any disease. We basically changed that to carry these scissors for us. It's just injected into the bloodstream. And once it's in the blood, it actually goes in and finds those nerve cells and introduces the scissors.

Chris - It sounds like the woman who swallowed a fly, and then swallows a spider to eat the fly. And we all know how that story ends. Because you're basically giving someone a virus to treat a virus. Is this safe?

Keith - This particular virus vector that we've used, called adeno-associated virus, is probably the leading vector that's being used for many, many types of gene therapy now. And there's several approved products out there, in the EU, and in the United States that use, adeno-associated virus, or AAV, to deliver different types of gene therapy. And so we're taking something that's quite proven to be safe, modifying it slightly for our needs, and then using it to try to cure an infection where we've simply not had any hope for a cure in the past.

Chris - You've been looking at herpes simplex virus, this causes cold sores, and it also causes genital disease. But this is one member of a big family of viruses that all work in a similar sort of way. Things like VZV, the virus that causes chicken pox, and then shingles in people unlucky enough to have that. Do you think you could prevent a person from succumbing to shingles by the same technique?

Keith - The shingles virus goes into very similar nerve cells and acts a lot like herpes simplex. And so we can actually think about using the same therapy for that virus as well. We're also very actively looking at viruses that are similar, but not herpes viruses, in particular hepatitis B. And we have some really exciting results there where we can do very similar things. We're likely to see success there and maybe in other viruses as well.


19:47 - One step forward for self-driving cars

Are self-driving cars actually going to be on our roads soon?

One step forward for self-driving cars
Peter Cowley

This week we are one step closer to a future of self-driving cars thanks to a new proposal the UK government is considering, which could see automated cars on the roads as early as next year. Our tech guru Peter Cowley told Eva Higginbotham more...

Peter - It's only a small step, but it's quite an important one. Basically, it's a call from the government for evidence for the safe use of automated lane keeping systems, or ALKS, basically staying in lane. So doing two things. One is not running into the car in front, of course, but also not leaving the lane, and although some cars already do that, they only do that with the driver having their hands on the wheel. In this case, this is actually allowing the driver to be aware, so it can take over if something goes wrong, but not be as involved as it would be at the current system. Of course, it has got to monitor whether the driver is actually still there. That he's still got a seat belt on, or her seatbelt on, monitoring eye tracking. It's got a black box in there, et cetera. And it will pass back control to the driver if it can't cope, but it's effectively the first time that the government's moving towards actually producing a legal definition of whether an automated vehicle can go on our roads or not.

Eva - Wow. So that's a truly hands-free type scenario. So what can, and can't self driving cars do already?

Peter - First of all, before we get too excited, these are under very strict conditions. This is an EU directive. It's being allowed throughout Europe from early next year. And this is only on roads where there's no pedestrians or cyclists, only when there's a central reservation. So basically only on the motorway or dual carriageway, and more importantly, no more than 37 miles an hour, or 60 kilometres an hour. Which means effectively, slow moving traffic. However, the UK government are trying to work out whether it's possible to do it up to 70 miles an hour, which is our speed limit in the UK. So how far have they got? There actually is no such thing as a self driving car on public roads yet. There are trials, and there are five levels of so-called autonomy. From the ones we see at the moment which are really levels one and two, to three, this is the first time that three, if it's allowed, will actually be on the road. But remember it's only in a single lane driving on a motorway, effectively. So it's a long way from the self-driving car.

Eva - I see, I guess one of the concerns is really, how much can we trust the average person to sort of use it safely and to also be paying attention while you know, having their hands off the wheel? What do we have to be wary of?

Peter - Yeah, that's a good question, because in fact, what it's trying to do is replace the average person with something that in principle should be safer. An automated system, if one believes in these things, means that they're less likely to make an error. So obviously they're not going to be drunk, or they're not going to be distracted by somebody in the back, et cetera, et cetera. So the average person isn't really relevant, it's whether one can trust the system to be effective, and mean that once it's enabled, that it works, but this person has still got to be available. They can't go and get a seat in the backseat, they've got to be available in case something goes wrong that the system can't cope with.

a photo of a plastic cup in the surf

22:50 - How much plastic is in the ocean?

Researchers estimate there's 10 x more plastic in the Atlantic Ocean than previously thought...

How much plastic is in the ocean?
Katsia Pabortsava, National Oceanographic Centre

According to a recent survey, the rise in home deliveries over lockdown has led to a 30% increase in the amount of plastic we’re throwing away. Of course, some plastic items are essential for fighting Covid-19, but the more plastic we use, the more that also ends up in the ocean where it breaks up into tiny particles called microplastics. These can concentrate toxins from the water and carry them up the food chain, potentially back into us. And while we knew this was a problem, we thought we understood the scale of it. That is, until now; because a team from the UK’s National Oceanographic Centre have discovered plastic levels in the Atlantic Ocean are considerably greater than we previously thought, as Phil Sansom heard from Katsia Pabortsava…

Katsia - We find at least 10 times more plastic contaminants in the ocean that we previously thought.

Phil - 10 times? That's quite alarming, isn't it?

Katsia - At least 10 times. So it should be more alarming. The fact that there are many of them and in this sort of quantities, it doesn't sound promising.

Phil - How big are the microplastics you're looking at, and what plastics exactly?

Katsia - We're looking at the microplastic particles, which are larger than 25 microns. So if a human hair is about 70 microns, you can do the math. It's nearly three times less. And we look at three most common plastic types, polyethylene, polypropylene, and polystyrene. So these are also the most littered.

Phil - Were you expecting there to be such a huge underestimate?

Katsia - Well, in the past few years, scientists were trying to solve the mystery of the missing plastic. We know how much we approximately supplied into the ocean in the past 65 years, but what we have been measuring in the surface ocean so far was just about 1% of that. But what we find in just the top 300 metres of the Atlantic Ocean, and just with three polymers of very limited size range, we find the quantities which are comparable to the amount that we have put in so far. So that is the striking finding of this study.

Phil - How did you go about then getting measurements from under the surface?

Katsia - We've got this wonderful opportunity to join a research ship that sails every year from the UK down to the Falklands, across the middle of the Atlantic. Every day we stop, and then we lower our instrumentation down into the ocean. They collect water samples or particles.

Phil - What's your instrument?

Katsia - Essentially, it is a pump loaded with a very fine filter. So what you end up having is all sorts of particles, including microplastics.

Phil - Is this the first time that anyone had done this? Gone out right to the middle of the ocean and lowered a filter on a line to get these measurements?

Katsia - For microplastic measurement specifically, yes. We were the first who has done it. The previous studies were measuring plastic, only in the very top layer of the ocean. And those studies were looking at larger plastic bits.

Phil - And we have all these qualifications, like, you know, you only measured above a certain size. You only looked at a few different kinds. You only looked at this area of the ocean, but given that you found this underestimate of 10 times, is that something that in theory might exist for other sizes, all sizes, all kinds of plastic. We just don't know it yet?

Katsia - Oh yes, absolutely. Yes. Previously we looked at fairly big plastic particles, and we found them in those concentrations. And then we also saw that those types of plastics are eaten by sea birds, or whales, or other organisms. Now we're talking very, very small plastic particles, and they can be eaten by much smaller organisms, and which then are eaten up by bigger organisms. So if they contain some sort of toxic or dangerous compounds in them, that would propagate up the food chain. And ultimately if a fish eats a lot of those particles, then we eat fish, the effects might be even reaching us. And that's why it is very, very important to tackle the question of exposure for all plastics, everywhere in the ocean. Because what our research looked at is just three polymers. It's a limited size range, and it's a small part of the ocean. And we already find so much.

photo of a green lawn

28:16 - How are gardens set to change?

With changing temperature and rainfall patterns predicted, how might our green spaces have to adapt in future?

How are gardens set to change?
Ross Cameron, Sheffield University

With changing temperature and rainfall patterns predicted by climate change, how might our gardens and vegetable patches have to adapt in the future? Ross Cameron is a landscape horticulturalist at Sheffield University and works on climate change mitigation; he’s co-authored a report for the Royal Horticultural Society on this topic, and he spoke to Chris Smith...

Ross - It's about extremes. It's about, generally speaking, drier summers and wetter winters, in a nutshell. There's some variation - Northwest Scotland, for example, might also have slightly wetter summers. But it's about pulling apart those weather conditions. So we're going to see drier spells for longer, but also wetter spells for longer. I guess one of the worrying aspects of it is it's not going to be a smooth ride. We're going to see a little bit more turbulence in the system. So we're going to see more oscillations, more extremes coming sometimes quite quickly after each other. So a very dry period followed by possibly a very wet period.

Chris - Of course, the plants that we are very fond of growing, and those plants that feed us very well, are not necessarily as fond of those sorts of changeable conditions as a weather person is. So what might be the implications for the plants we can grow? Do we expect that some things are just not going to be viable anymore? Is this the end of the English country garden?

Ross - We can deal with the weather by putting on a coat, taking the coat off sort of thing, but plants can't. Plants are very much in tune to their environment and the seasons. So they go through periods of acclimation so they can adapt to drought if they're given a bit of a chance to run up to that drought beforehand. So these conditions are quite challenging. We're going to see plants that are traditionally grown in warmer climates. They may adapt. They may be useful in the garden. We may see more of those types of plants. At the same time I think we're also going to see plants who are just kind of generally speaking more resilient, more tolerant to stresses in general, and trying to bring in that sort of resilience. Unfortunately, that often means the plants that are quite competitive, quite successful already. So things we might sometimes define as slightly weedy, they'll be the ones that are the survivors in some ways.

Chris - So in my case, lots of stinging nettles. When you were talking there I was thinking about the fact that if we do see a lot of rain all at once, we get these big deluges. Is there a risk that you could end up with leaching? So the rain comes down on the soil, it washes out nutrients. They go into the river, not good news for silting up rivers, but also not good news for the soil. So gardeners are then attempted to put more fertilizer on and that gets leached as well. There could be a vicious cycle there.

Ross - Yeah. So we're going to be careful about how we manage our gardens, not putting too many chemicals onto the system. We have some allies in that - we have things like organic matter. So the more we can recycle compost, recycle horse manure, all those sorts of things that have been traditionally useful for improving the soil. They're actually quite beneficial here because that soil organic matter helps act as a sponge and hold water when there's too much. But also it helps keep that water up when it gets dry and provide it to the plants. So all gardeners always say, feed the soil to feed the plants. And that adage is still quite true, I think.

Chris - And you mentioned water and keeping water in the soil, but what about keeping water not in the soil, but in things like water butts? Is this all going to be about better water stewardship? If we anticipate we're going to have a long run of dry days and we want to grow the same plants, we just need to make sure we store up water for the bad times when we've got the good times as it were.

Ross - That's right. If rain comes in bigger dollops, then we want to capture that and reuse it really for garden use. Rain butts are a great idea, but we're also seeing interventions in places like Australia and North America, particularly, in things like rain gardens. So you actually sculpt out some of the landscape where water can be held. That water runs off very quickly. You avoid it going into the houses and the roads and you collect it in certain places, and then that can then be pumped out to actually irrigate farms and gardens later or itself becomes a feature in the landscape. So it can be quite small scale things, or it can actually be almost at a community level that you're trying to capture and hold water.

Chris - Well, more on that sort of thing in just a second because I'd just like to play you, Ross, a little clip we recorded at a special dry garden that's being developed at the Cambridge University Botanic Garden.

Chantal - It's called the dry garden, because there's a permanent hosepipe ban in here.

Katie - There is no water in this garden?

Chantal - No irrigation, no watering. That's really the idea. It's surrounded on all sides with these quite tall hedges. Those can provide shade as well. Enclosed reduces impacts of wind. So if you can reduce that wind and you can provide the shade, then you are providing some sort of micro climate that allows some of the plants that may be less drought adapted to survive. But then you need to think about the plantings. And this comes back to selection of those kinds of plants that have that adaptations to the dry environment. But the practical activities to ensure that water doesn't get lost in this garden are things like mulching, so mulching often. Having this surface layer of organic material, bark cuttings, or minerals like gravel, all of that will reduce moisture loss from the soil surface. No lawn, permeable paving that allows the water to move through the landscape and doesn't result in if there is a heavy rainfall - now we're predicting more rainfall in winter on the other hand to drought in the summer - so you want to make sure that your surfaces are permeable, you're not going to increase your flooding.

Chris - So basically it's more sympathetic planting and a bit of forward thought.

Ross - Yes, indeed. Yeah. It's the right plant for the right sort of situation. And I think that will vary slightly in the different areas of the country. So the areas that are wet at the minute and get wetter you might be thinking of certain types of intervention and planting. Somewhere like East Anglia, the east side of the country, then you're thinking about things like scree gardens, where you're using dry adapted species more effectively. And you can get the balance right. You can keep these guys going quite happily in the summer, but keep the roots above any water table that might appear in the winter through slight changes of level in the garden and using things like was mentioned there - shale, and other sort of mulch systems.

Chris - Is it all bad news? Are there any silver linings to this longer growing season et cetera because the temperature's a bit different? Are there any things we can look forward to?

Ross - From the personal point of view, us, we will enjoy the garden more. We'll be outdoors more often. I think we will be using the garden as that outdoor room. And we will always obviously still grow plants and containers where you can, to some extent, mollycoddle them and look after them. So we will still have our special plants, our pets, but it may well be that we're actually having more time and using the garden more effectively just because we are having these longer summer dry periods.

photo of a lavendar plant

35:32 - A walk through the garden

We took a turn around Cambridge University Botanic Garden's climate change and plants trail...

A walk through the garden
Chantal Helm, Cambridge University Botanic Garden

Back to the Cambridge University Botanic Garden where they’re exploring the collision between gardens, plants and climate change. Katie Haylor went for a walk with Chantal Helm...

Chantal - We're having summer high temperatures, I suppose, as part of climate change predictions that are becoming reality. And here in Cambridge being probably the driest part of the UK and probably the driest area in Western Europe, we deal with high temperatures and low rainfall quite often. I think with these increased temperatures, the moisture deficit within the soils is becoming more and more of a problem to deal with.

Katie - You've got a new trail in the garden?

Chantal - All about plants and climate change, yes. Comes out of hope to try and encourage our visitors to appreciate plants for their diversity in terms of their adaptations to climate change. Also to, I suppose, encourage our visitors to understand why we are going certain ways with certain plantings and also to really talk about how plants can help in mitigating climate change. There is a lot of climate modelling that is trying to group plants into the winners and the losers and plants that are already adapted to dry, hotter conditions, potentially going to be the winners. And then those plants with much more specialist requirements are probably going to be the losers. So we're talking about plants that are probably adapted to very high altitudes.

Katie - But we're here in the Mediterranean garden, these plants are designed to be in hot dry conditions, right?

Chantal - Yep. So the Mediterranean - hot dry summers is the key thing. And I suppose more rainy, wet winters is what they're able to survive. Very sandy soils is the other sort of thing, so that there's a sort of drainage in the summertime. So reduction in leaf surface area is a big key one for many plants, lavender and rosemary we're familiar with, they will have very small leaves.

Katie - So what's going on there is that because you've then got less area for the water to evaporate?

Chantal - Exactly. Some plants have gone to the extreme where they've lost their leaves entirely. There are a lot of succulent plants, for example, even maybe cactuses and stuff like that, you'll have no leaves. And the only thing you're seeing there, the leaves, are actually the thorns and that is an adaptation for a dry environment. So those can do quite well if they're able to deal with the winter temperatures that we have in the UK. So with a Mediterranean planting and a garden, you've got to think about the whole year, the whole season, even though it may have some good adaptations to summer drought, is it able to survive frost? Many of the plants have got hairs and maybe are grey, so that's all about reflecting light, making sure that the heat doesn't impact on the photosynthetic capability of the plant. But also the hairs will track moisture close to the leaf surface.

Katie - So what about the losers?

Chantal - If we come back to the issue with high altitude plants, especially Alpine plants, for example, many of them have adapted to an extreme environment in growing which is rapidly disappearing. So obviously as temperatures rise, we are going to have increasing temperatures that's going to move up a mountain environment. They're going to lose space. Depending on where they are in the mountain and the sort of micro climate, the topography of that mountain, there may be opportunities for them to hide out, but there's also this competition with other species that are also moving up the mountain. They may be faster, better competitors, may grow faster. Alpine plants tend to grow very slowly because of the extreme environment and extreme conditions they're having to survive in. So there is sort of those losers. The physiology depends on the mountain itself and whether they're going to be able to survive or not. So we've got a giant Redwood. They've been here for 150 years. Some of the largest plants in the world, they don't obviously grow to their natural size here in the garden, even though they are 150 years old, because of various constraints. But this plant is useful in the climate change trail because it can show how much carbon a large tree like this can lock away. I think it came up to 50 tonnes of carbon dioxide, the same as eight return flights from London to Sydney

Katie - On the one hand, that sounds pretty impressive. But on the other hand, that's a lot of trees, right?

Chantal - Yes. And if you think how many flights there are, obviously every day, all the time, to different locations, the idea of planting trees to offset all of our carbon emissions is probably not going to be a very sustainable thing. It's just not enough land. And I think that's what we're trying to sort of bring home with this point in the trail.

Katie - But it's not just individual plants that can mitigate against some of the impacts of climate change, is it, I'm pretty sure you've got a landscape or a type of environment on this trail somewhere as well?

Chantal - Yes. So the other point in the trail is the Fen display being a carbon sink.

Katie - Very fitting for Cambridgeshire! Can we go and have a look?

Chantal - Yes, definitely.

Katie - Just to describe where we are, we've come into an area - it's waterlogged. What classic plants would you find in this kind of Fen environment?

Chantal - You got a lot of sedges, and a lot of reeds. If you have the water logging taking place over an extended period of time, you will then have the buildup of the peat, which then provides that substrate in which all the plants are then growing.

Katie - And what exactly is peat?

Chantal - So peat is an organic material that is formed over time through very slow to no decomposition of organic material, dead plants, pretty much. In terms of a very low oxygen environment, the decomposition is very much slowed. So the organic matter is built up, maintained within that environment, so it becomes the substrate. It has got a very wonderful structure that in terms of water holding capacity and other features that make it very good for composting and providing structure to your soils and gardens, and hence has become very popular in horticulture for many, many years. Though, in recent decades, we realise that peat is actually locking away carbon. The extraction of peat, the whole industry is releasing huge amounts of CO2 into the atmosphere, which would have been locked away. Not only that it's also this rare habitat that's sort of been destroyed for that peat to be extracted for our gardens. Most of our natural Fen habitat has actually been lost in the UK. It would have been extensive in this East Anglian region because of water log conditions, very low lying land areas. That was all drained a while back for agriculture. Agriculture was working very well for a long time in the environment because the soils, once you've drained them, they have very high nutrients, but the loss of this habitat has resulted in the loss and extinction of a large number of different species. So the whole Fen land area, in terms of agriculture, is sinking for one in that as the peat degrades, it's no longer waterlogged. The carbon is being broken down. It's released as carbon dioxide, and that is then increasing the amount of carbon dioxide that's coming up. So now the whole area is actually a carbon source where it used to be a carbon sink. So it's a very rare and protected habitat and we're trying to recreate it here.

a photo of butterflies

42:32 - Butterflies and climate change

What does climate change mean for butterflies in the UK?

Butterflies and climate change
Andrew Bladon, Cambridge University; Ross Cameron, Sheffield University

We can’t talk about plant life without mentioning the animals that live in and around them. And pollinators are often in the news, with worries around declining numbers, and the impact on biodiversity and crop production. Andrew Bladon works at Cambridge University, where he’s done field work - literally - looking at how butterflies respond to temperature change. And he spoke to Chris Smith...

Andrew - So like many species, butterflies are showing effects of climate change at the population level. So we've seen that species are moving North in Europe and North America. And similarly to the plants that Chantal was talking about, species that are adapted to mountains tend to be declining and they're becoming more and more restricted. And there are also changes in behaviour. So species start to emerge earlier in warmer years. But all of these sort of population level changes that we can detect are likely to be caused by individual butterflies' responses to temperature. But we actually know very little about how butterflies respond on an individual level. So what we were trying to find out was exactly that - what do butterflies do to respond to temperature at fine scale? And can we link that to what's happening at a large scale?

Chris - And of course, the butterflies that do inhabit different environments that have different ranges of temperatures are going to be affected differently, in the way that you've just been identifying. So are there therefore some winners and some losers here?

Andrew - Yeah. So the interesting thing is that at the population level, research by butterfly conservation and long term monitoring over the last 40 years has shown that despite the fact that our climate is probably improving for the majority of species, about two thirds to three quarters of our species are still declining. The suspicion is that that's because there's still a big effect of habitat fragmentation and habitat loss on species. But within that, there are a few, a small number of species that are doing quite well. And species that are expanding their ranges northwards quite rapidly. And those generally tend to be the species that are more ubiquitous. They're the ones that can do well in lots of different environments. And they can survive in lots of different environments.

Chris - So the winners just win more and the ones that are already a bit vulnerable, they're finding it even harder to cope. Do you actually know, when you look at those winners and losers, do you know what it is that sets them apart? Why some are just a bit more resilient and some are more vulnerable?

Andrew - That's something that we've been looking at specifically in terms of how they adapt their behaviour to different temperatures. But I'm going to hold off a little bit on telling you the results of that, because we've got a paper coming out in a couple of weeks. So if you watch this space, there should be more answers coming very, very soon. In general, as, as you'd expect really, species that are more able to cope with a broad range of temperatures, those that are able to adapt generally to a wider range of temperatures, tend to be doing better. And those which are very specialist and have very specific temperature requirements tend to be doing worse.

Chris - What about the services they provide to the plants? I started this by referring to the fact they are pollinators. People often overlook the role of the lepidoptera - butterflies, moths etc - in terms of their contribution to the pollination effort. What has been the impact of these changes on what will be the impact of these changes on our plants and flowers and crops getting pollinated?

Andrew - Yeah, so you're exactly right. So about 85% of crops within the EU are insect pollinated. And most people assume that that's all done by bees. But in fact, honey bees, which people think of as the most common pollinators, only actually pollinate about five to 15% of crops, which leaves the other 85 to 95% to be pollinated by bumblebees, solitary bees, moths and butterflies, hover flies, beetles, and all sorts of other insects. And so actually the diversity of the insect community is really, really important for crop pollination and is estimated to be worth hundreds of billions of pounds annually.

Chris - And so if we take your findings and we extrapolate them to what the impact might be on pollination of crops, does that mean it's automatically a worrying picture? Or is it just that because we don't think the overall numbers of pollinators are going to go down, just the diversity is going to drop, actually, we probably will get away with it?

Andrew - The loss of numbers is worrying, but as you say, because some are going up, there's potentially some buffering there, but the thing is that because insect numbers fluctuate quite wildly from year to year. And so some species will do well in one year and then badly another year. And at the same time, a different species will do badly in the first year and well in another year. And by having that diversity of insect pollinators in the landscape, it means that actually we can be more resilient. So in any given year, we've got more options for the species that can pollinate our crops. The worrying thing is that if we lose some of that diversity, we become less resilient. And so there are fewer options for species to pollinate and therefore the chances of us having a really bad year where pollination fails becomes more and more likely. And, actually, the reliance that we currently have and is developing worldwide on the honeybee for pollination is particularly worrying. Because essentially if something bad happens to honeybees, we've lost the diversity of wild insect pollinators that could be able to pick up the pieces.

Chris - What can gardeners do to help?

Andrew - One thing is plant a wide range of wildflowers, to help give insects a helping hand, things that flower throughout the season. Another thing is to try and reduce the use of pesticides and herbicides because they are directly killing our insects. And the final thing is to try and actually be messier in the garden. Mow less, and leave some taller vegetation, which helps insects to survive through the winter.

Chris - Andrew, thank you.

We also put this to University of Sheffield horticulturalist Ross Cameron...

Chris - So, Ross, basically mow less, chuck fewer chemicals on, have a messier garden. Would you go along with that?

Ross - Yeah. In principle, I would. I mean, I think we can go back to nature a little bit in the design of our gardens in that the slightly rougher approach provides a lot of benefits. It's a benefit for wildlife, but even for what I mentioned earlier about capturing rain, holding water, the ability to provide a better microclimate for wildlife, but also for ourselves, goes along with a slightly more relaxed attitude to gardens. And at the end of the day gardens are places we want to enjoy. And quite a lot of enjoyment comes from seeing nature. So gardens without butterflies, without birds are pretty poor soul, really.

Chris - Lawn. A well manicured lawn is often seen as the thing we all aspire to, but actually one person described these things as a sort of biodiversity desert, a horrible mono-culture that's very, very demanding on our time, of our input and returns very little value. A) is that true? And B) therefore, should I get rid of my lawn? And if so, what should I replace it with?

Ross - Yeah, the green desert! Look, manicured lawns have their place. If you happen to be in the luxury of having a croquet lawn or a grass tennis court, it has to be close mown and functional. The reality is most of us do a lot of management of our lawns, which are not necessarily to our benefit. You can let the lawn grow a bit longer. You can get the wildflowers coming in. You can have the pollinators and insects, and you can also retain that degree of respectability. We're using what we call "cues to care". So if you cut paths where through it, if you keep certain parts of it tidy, you can actually still have the best of both worlds, nice legible walkable paths through the garden. And at the same time, allowing some rough and ready spots within the lawn that actually attracts the wildlife and provides that resilience.


49:57 - Plant pests and pathogens

What impact is climate change predicted to have on plant pathogen species?

Plant pests and pathogens
Sebastian Eves-van den Akker, Cambridge University

From creatures that live in harmony with plants, to plant pests, and as 2020 is actually the international year of plant health there’s no better time to be talking about them. Climate change will affect these pests too, potentially impacting our ability to grow enough food. This is what Sebastian Eves-van den Akker studies, and he’s particularly interested in nematodes, and he spoke to Eva Higginbotham...

Sebastian - So nematodes are for the most part these microscopic worms, and although most people probably haven't ever heard of a nematode, they are incredibly numerous. So if you were just to count all of the animals on the planet, one by one, then nematodes would account for more than half. So, you know, on average, most animals are nematodes. There's this great quote by a famous Nathan A. Cobb. And to kind of paraphrase. He says that if you were to remove magically all of the matter on the planet, but you left the nematodes in place, you would still be able to see faintly the hills and the valleys and the fields and the rivers, simply by the nematodes that used to live there.

Eva - Sounds like an incredibly well kept secret! So if they're everywhere, where do you actually study them?

Sebastian - Most nematodes are, you know, kind of good guys, right? So that is, you know, important parts of many different ecosystems and they carry out many important ecosystem services. So for example, they can eat detritus and things like that. But a few of them have evolved to be parasites. And as you say, this year being the international year of plant health, what we work on is global food security. And some of these parasites parasitise plants, and are a major threat to global food security.

Eva - I see. And so how do they actually cause disease? What makes them parasitic?

Sebastian - The kind of nematodes that I work with are soil born, they live in the soil and parasitise the roots of plants. And what they do is they move inside the roots of the plant and they make the plant make a tumour. Now this tumour is really the wrong word, but it's got the right kind of connotations. This tumour is this new tissue that forms inside the plant that drains the plant resources and that the nematode eats. And so you can imagine if you've got lots of nematodes making the plant make this structure that it doesn't want, and that's draining the resources, ultimately that can damage the plant.

Eva - What kind of crops do they affect, or do they affect plants other than crops as well?

Sebastian - Basically every plant in the world. So there's at least one species of nematode for every major food crop of the world and indeed, most plants of the world. So if you've got a plant there will be a nematode that can, parasitise it, whether it's on your plants or not.

Eva - What might climate change do to them? Are they looking to have a good time or a bad time with what we're expecting to change in the climate, particularly, maybe in the UK over the next few years?

Sebastian - It's really hard to predict. I mean, we can definitely say that it will have an impact. So climate change will have an impact. But saying what that impact is going to be is going to be a challenge. So for the particular kind of nematode that we work on, which are called potato cyst nematodes (un-surprisingly they parasitise potatoes) and in the UK is there are actually two species. And one of which likes it hot and the other one, which likes it cold. And so in this case, we actually know quite clearly that if, for example, the average temperature and in particular, if the minimum temperature in the UK increases, then this one is going to do better. But in most cases actually predicting the dynamics of how that's going to change is actually quite challenging.

Eva - I guess it's something of a complicated relationship between the nematode and the plant in those cases, because they are parasites. Is there anything we can do to stop them?

Sebastian - Yeah. There's number, different ways you can control nematodes or indeed any plant disease. I mean you know, we're all thinking about immunity at the moment, you know, with what's going on the health crisis. And so we're familiar with this idea of hosts being immune to parasites and diseases. And of course, plants have immune systems as well, but their immune systems are quite different from animals. And so on the most part, plants don't have an adaptive immune system. They have an innate immune system. And I find it quite remarkable that, you know, most plants are immune to most diseases, even though they haven't seen them. Whereas for example, with, for an animal to become immune to some diseases they would have to have some experience of that. And so immune plants is one of the best ways that we can, we can combat these, but there are other ways, you know, that involve inputs, for example, pesticides, or by, you know, managing your crop in rotations and things like that.

Eva- I see. So the sort of ideal scenario is just to have a plant that isn't vulnerable to these nematodes.

Sebastian - I mean, that's the golden bullet if you like. But you know, you never count against evolution. And so if you have plants that are immune, ultimately you will get nematodes or other pathogens that can find a way around that. So really a diversity of approaches is the best way.

Eva - So nematodes are everywhere, but what about other diseases that can affect plants? Are they likely to be a problem too?

Sebastian - Yeah, absolutely. I mean, there are loads of different diseases of plants. They can be restricted to different parts of the world geographically. And you can imagine that some of those, either those diseases themselves or their vectors, will like different temperatures. So again, if the climate changes in the UK, then it's likely that this will make the UK more suitable to some of those other pathogens, or less suitable.

Eva - So different viruses, different kinds of bacterial infections that could affect plants?

Sebastian - Exactly. Yeah. So one that people have heard of a lot in the news recently is Xylella. This is a bacteria that infects plants, and this is sort of, you know, on the borders of the UK, if you like, but can't quite make it.

Eva - And that might change with climate change?

Sebastian - Exactly yeah, it's restricted by temperature.

Water swirling into a vortex.

55:28 - QotW: Why stuff collects at a whirlpool's centre

"Why do particles go to the centre in a bucket of water?" This is the question we're tackling this week...

QotW: Why stuff collects at a whirlpool's centre

Phil Sansom made a splash answering this question, with the help of fluid dynamics expert Dan Nickström...

Phil - Jonathan, I don’t blame your dad for not knowing - the thing you describe is actually a phenomenon that confused physicists for ages. They called it the ‘tea leaf paradox’ because they saw it happening when they stirred their tea. Then, about 150 years ago, they managed to solve it. And now, Dan Nickstrom from Maynooth University is here to solve it again for us.

Dan - It's a very interesting phenomenon! It's all got to do with how the water moves after you stop spinning and the fact that it is dragging the particles along with it. If you look at a clear bowl full of water from the side, you'll notice that when you spin it the sides go up really high and the centre goes down low. This is because the centrifugal force from you stirring pushes the water out towards the edge, and it is pushed upwards when it hits the side of the container.

Phil - Centrifugal force is a force that pushes a spinning thing outwards, and its often called a fake force because what’s really going on is the water wants to move in a straight line, and it hits the edge of the bucket. That just makes it look like its being forced outwards, and the result is this whirlpool with high edges.

Dan - When you stop stirring, the interesting part happens! The water at the edge (and the particles it's dragging with it) gets pushed downwards by gravity. The water in the centre in turn goes back upwards. This means the water at the edge flows down to the bottom, inwards to the centre of the bucket, and back up to the top again. This loop repeats over and over as it’s all slowing down. The particles are dragged along like this too! It's all very complicated!

Dan - As it gets slower and slower the force pulling the particles gets weaker and weaker until it's not able to fight against gravity and can't pull them up at the centre. This means they get dropped at the centre! One after the other, until they're almost all there.

Phil - I just did this myself in my kitchen, and Jonathan is 100% right - the little bits of schmutz do all end up in the centre. All thanks to the pattern the water flows in. Thanks Dan Nickstrom. Next time, we’re leaving water behind, and talking about an entirely different liquid, thanks to this question from Charlie...

Charlie - Maybe this is just me, but it dawned on me that whenever I have to hold in a pee, the need to go increases exponentially when I know that relief is close. Why is this?


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