Are trees the answer to solving climate change?

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Right.

Deep breath in

and out

and welcome to Inside Science.

And what do you think you've just inhaled in that last lung full of air?

I'll be finding out with science writer Carl Zimmer.

And quick quiz, five points if you can name that bird.

It's one of the most common in the UK, but that chirp is becoming rarer.

Answer coming later when we find out why.

And I have a science squad here with me today.

First Lizzie Gibney, senior science reporter at Nature.

Lizzie you're here to take me through your pick of the exciting new science research this week but before all that I should say last time we met was on a German ferry surrounded by significant quantities of quantum physicists right?

That's right we were both on our way to the biggest quantum party of, well, the century.

It's 100 years since quantum mechanics was was first formed.

So more on that later.

But first though, I should introduce my other guest, Mark Maslin, Professor of Earth System Science at University College London, and my go-to on checking climate facts.

So that's why you're here, Mark.

Welcome.

I'm absolutely happy to check all the facts.

Good.

I've asked you here because there's a new warning out today from scientists that trying to offset carbon emissions by planting trees alone just won't work.

They've got the numbers.

Just wondering, is this a massive U-turn in our understanding of the roles trees play, or is this just another warning about how hard it's going to be to manage global warming?

Mark, this got the team thinking about where the news leaves us in terms of a plan for us, trees and the planet.

So we've put together our top five questions about trees and carbon.

Are you ready?

I'm ready and I'm going to branch out and talk about trees.

Good tree pun.

Where are we at the moment?

We know we need more trees to take more carbon dioxide out of the air.

Are we still cutting down more trees than we're planting?

Yes, it's the simple answer.

We are doing a lot of deforestation, particularly in the tropics.

I have to say, even though there's been a change of government in Brazil, there is still deforestation, but it is at a much reduced rate.

But other countries in Southeast Asia, like Indonesia, are still cutting down rainforest to actually allow there to be land for expanding agriculture.

However, if we balance that, other places are planting trees.

Now, a lot of them are commercial, they are for logging and they are for timber, but we're having this balancing act.

But at the moment, unfortunately, we're in a deficit.

We are still cutting down more trees than we plant every single year.

Okay, which leads me to question two.

How many trees trees do we need to plant to stop CO2 levels rising any further?

So the paper that's just come out is literally just telling us something that we've known for decades, which is planting trees is really important for many environmental reasons.

It can also store some carbon.

But I'll give you some numbers.

Humans have cut down three trillion trees on the planet.

So that's half the trees on the planet have been cut down by us.

If we replant one trillion, okay, that's the area, the land area of the United States, that would suck out the equivalent pollution of one year.

So if you think about it, if we replant all those three trillion, we'd only be taking out three years of global greenhouse gas emissions.

So it's very simple.

The way we deal with climate change is we stop burning stuff, we stop putting stuff into the atmosphere.

However, again,

reforestation is really important for the local environments, but it's also important because there are some stuff that we just can't get to zero.

So, for example, think about agriculture, aviation, and concrete manufacturing.

Those are really difficult to actually remove the carbon and the sort of like emissions that we're producing.

So, we need some way of offsetting that.

So, reforesting could be a really nice way of doing it.

But reforestation is not the solution to climate change.

It never was and never will be.

Okay, so question three, is planting trees actually the best approach?

So it's a very good approach for the right area.

So my go-to example is China.

In the 1990s, the western part of China was becoming a dust bowl.

Think 1930s USA, you know, sort of you've seen all the films, etc.

That's how bad it was getting.

And this was the breadbasket of China.

This is where all the agriculture and food was being produced.

And of course, the Chinese went to their scientists and said, what's happened?

And they went, well, you cut down all the trees.

So they went through this reforestation.

They reforested about a hundred million hectares, huge.

And what was happening is they realized that once they planted the trees, they stabilized the soil, tick.

They stopped flash floods, tick.

They also put so much moisture into the atmosphere that they stabilized the regional rainfall and made it much more predictable.

And of course, agriculture production went through the roof.

Win, win, win.

Oh, and it stored carbon as well.

Okay, so that's a good news story from China.

Is there anything else in the arsenal that we could use asides from planting trees?

I'm just thinking if there's a not enough land mass, if say America's already full, I don't know, could we seed the oceans with algae?

Is that a possible?

So I'm going to play devil's advocate because one of the really interesting thing is our population is expanding.

We're at 8 billion and we'll hit about 10 billion by the middle of the century where it will stabilize.

And we think, oh my God, all these people.

However, they're moving to cities.

So the interesting thing is the world is becoming a wilder place.

There are now more and more locations that have no one living there, which is prime targets to reforest.

So remember, forests are in the temperate zone, so we can have forests in sort of like North America, Europe.

We can have lots of forests in the UK if we want to, as well as the tropics.

So we have lots of space to do that.

So that's the first thing, tick.

Second thing is, of course, we might actually not have to do as much because we might switch to renewable energy, move to the 21st century with clean energy and stop polluting the atmosphere.

We also have other technologies, so we can capture carbon from sulfide power stations and we also have direct air capture, where you literally suck CO2 out of the atmosphere.

It's not very efficient, efficient, it's very expensive and actually, as I jokingly once said, why wouldn't you just plant some nice trees?

So not all forests are equal though, are they?

Question four, where would we plant and what would we plant?

So in the tropics what you really want to do is not cut down forests.

That's true everywhere, okay?

Because mature forest already stores the carbon, already has all that biodiversity.

If that's already happened, then what we want to do is reforest.

So you want to actually put similar trees back because they're an ecological fit, they are suitable to the climate, and you want to be able to do that.

But that can happen everywhere.

If we take the UK, the UK got down to 3%

forest cover after the First World War because we cut down lots of trees to make ships to keep the French out.

And then, of course, we cut down even more trees to make the trenches.

Since then, the Forestry Commission has actually produced lots of ways of encouraging forests, and we're up to about 13.5%.

But the average in Europe is 30%.

So we could actually reforest a vast area of the UK,

which would give us a little bit of help to get to our net zero target by 2050.

And question five, final one.

World leaders have promised to end and reverse deforestation by 2030.

Is that doable or is that pie in the sky?

So it's interesting because world leaders keep mentioning this and keep saying this for the last 20 years.

It is if we can shift the emphasis and I think making sure that countries value their natural resources and it isn't being exploited by other countries.

So one of the conversion rates of particularly tropical rainforests is for agriculture.

But we already produce enough food for 10 billion people.

There's only 8 billion people in the world.

So we have a global system that we're overproducing food and we're producing it in a really inefficient way.

So how do we actually as a global system think about, hang on, do we actually need to clear any more land because we're producing enough food?

How do we support those countries that rely on their agricultural products to produce money?

to then develop and produce sort of like better conditions for their people.

So I think there's a a lot of politics in there about development, but we can incentivise them not to cut down their forests.

And some countries, I think Costa Rica, Gabon made decisions decades ago and said, this is our forest, this is pristine, this is our legacy, we're not touching it.

Professor Mark Maslin, thank you very much.

I think we've just reinforced how important trees are for removing carbon dioxide and adding oxygen to the air we breathe.

The recent COVID pandemic made us all horribly aware that each lung fill also contains an entire ecosystem that we can't see with the naked eye.

It was also the trigger point for science writer Carl Zimmer to write his latest book, Airborne, The Hidden History of the Life We Breathe.

He joined me recently to share some tales of how we discovered these hidden worlds.

The air has been teeming with life pretty much since life began, but it's been a long time for us to really appreciate that.

And during the COVID pandemic, that actually became a source of real scientific conflict as to how COVID was spreading.

And in fact, COVID is airborne, as we know now.

This whole question of airborne life, aerobiology, airborne disease, this has a long history, a long, fraught, battle-filled history.

Tell me a bit more about that history.

Can we go back to when we first realized that air is in fact teeming with life?

So that really started to come into focus in the mid-1800s.

So for example, the Irish potato famine was this devastating outbreak that was destroying potatoes and killing, you know, over a million people in Ireland.

And it was kind of a mysterious how it was spreading.

And, you know, some people were maintaining, oh, it's just that these potatoes are rotting because the weather conditions are bad or there's some sort of mysterious miasma or something like that.

But there were some naturalists who said, no, we see there's an organism growing in these potatoes causing the disease, and they must be able to travel from potato to potato and must be able to travel from farm to farm and from country to country through the air.

With the Second World War looming, governments worked out that, well, if you can use this biology to check for potentially bad diseases, you can can also use it to seed them.

That's right.

In World War II, the American military and the British military, they were very worried that

Nazi Germany and Japan might be using biological warfare.

In other words, creating weapons made from bacteria and other pathogens.

And so Britain and the United States, as well as the Soviet Union, they were all building up their own programs.

And in the the United States in particular, the Army built a huge facility and looked at what the aerobiologists of the 1930s had been doing.

The U.S.

military said, well, what would it take to attack the crops of another country?

And so they actually were crafting these bombs that are full of fungal spores.

Other researchers in the 1930s had worked out how human diseases can spread from person to person through the air, through droplets or through dust and so on.

And so the military said, well, we're going to use their ideas and even literally their scientific equipment to actually figure out how to design the deadliest weapons that can kill people as effectively as possible.

So imagine an anthrax bomb that gets dropped on a city and those spores spread out and are optimized to be inhaled and then to become incredibly deadly.

Given that you've just written the book on aerobiology and you know you reported through COVID, what are you doing differently now?

I bought myself a carbon dioxide monitor while I was working on the book because I just noticed that all the scientists I was talking to, they had them too.

And it's just something that measures the concentration of CO2 in the air around you.

And it's a good way to get get a quick sense of how well ventilated the space is that you're in.

Because if you're with people where the windows are closed, you know, the concentration is rapidly going to increase because everyone's exhaling carbon dioxide.

And if one of them has measles, tuberculosis, COVID, influenza, a whole list of other diseases that can spread through the air, you know, those pathogens are in the air too.

They're floating around in invisible droplets.

And so if I'm in a room and I notice that the concentration is going way up, you know, I might look around and be like, hey, you might have opened that window.

I mean, it's a simple thing to do, and it can make a big difference.

Is there any interesting new science that you came across that would help us, I don't know, more easily detect problems in the air or fight against them?

The Biden administration put up $150 million in a project that will be really exciting if it gets off the ground.

And in this age where the U.S.

government is massively cutting science research funding, I don't know if it's going to get off the ground.

But the idea is that you would

build like a carbon monoxide detector, but for pathogens.

It would sample the air and it would be able to actually sequence the genes of anything that it encountered in that air.

And then in real time, would be able to say, like, you know, warning, like there is, you know, H5N1 influenza in this room, or there is measles, or there is some virus that I've never seen before.

That would be amazing.

Carl Zimmer, author of Airborne, The Hidden History of the Life We Breathe, thank you so much for coming on to Inside Science.

Thank you.

It was a real pleasure.

Sucks, the new musical has made Tony award-winning history on Broadway.

We demand to be hosted.

Winner, best score.

We demand to be seen.

Winner, best book.

We demand to be quality.

It's a theatrical masterpiece that's thrilling, inspiring, dazzlingly entertaining, and unquestionably the most emotionally stirring musical this season.

Suffs, playing the Orpheum Theater, October 22nd through November 9th.

Tickets at BroadwaySF.com.

You're listening to Inside Science.

I'm Marnie Chesterton, and I'm not going to leave you hanging any longer.

Did you identify this bird correctly?

Sadly, no cash prizes, but a warm glow of satisfaction if you said sparrow in our little quiz at the start of the programme.

Back in spring, we reported on the plight of some of our UK wild bird species, and among them was the humble house sparrow, which turns out to be a listener favourite.

Here at Inside Science, we were blown away by your response to the news that the sparrow numbers in the UK have fallen off a cliff.

You wanted answers, so we asked Imperial College's Dr Julia Schroeder, with 15 years of sparrow behaviour research under her belt to give us a deeper dive into the disappearances.

Who doesn't love a house sparrow?

Their cheerful chirps from rooftops, their busy foraging in parks or streets, it's really difficult not to marvel at them.

These little birds have evolved alongside humans for at least 10,000 years.

They started associating with us during the advent of agriculture in the Fertile Crescent and since then have followed humans into most of Eurasia and Northern Africa.

Today, house sparrows are perfectly adapted to cohabiting with humans in these areas, nesting in their roofs, crevices, farms, and towns.

They really like living around people and they don't just nest in our buildings, they also thrive on our mess.

Spilled grain, chicken feed, and even leftover chips outside a kebab shop make for reliable meals.

For house sparrow chicks, the insects found near our livestock offer all the protein they need to grow.

However, house sparrows did not stay put in Eurasia and Northern Africa.

European settlers to the Americas missed them so much that they introduced them to their new land.

From there, house sparrows spread to every continent except Antarctica.

In sub-Saharan Africa, Australia and New Zealand, they're actually still expanding, often along railways and other transport routes where grain and food are plentiful.

Most people today enjoy the presence of house sparrows but that hasn't always been the case.

In Mao Zedong's China they were accused of stealing too much grain.

In a campaign to boost harvests Mao ordered the extermination of all sparrows.

However, the result horribly backfired.

Without sparrows to control them, locusts surged and devastated crops, even leading to starvation.

This is a powerful lesson about the importance of ecological balance and how, of course, animals that may appear to take from us can actually be beneficial to humans.

And even today, in the Americas, house sparrows are seen by some as pests, but elsewhere, a very different problem is emerging.

In the UK, house sparrow numbers have plummeted by on average 68%

and in some areas even up to 90%.

Similar declines are being seen in major cities across South Asia and North America.

So what might be driving this?

Well, the answer lies in a combination of factors, all of which affect the production and the survival of chicks.

This is because while adult sparrows may still find food, the chicks really rely on insects to grow.

But insects have declined drastically recently, especially in cities.

Think about it.

When was the last time you were bitten by a mosquito in a city?

Another culprit is noise.

In loud urban environments, mother sparrows often can't hear their chicks begging for food.

And if they don't hear them, they will feed them less.

It's a real tragic miscommunication.

And perhaps the saddest reason is we have made our houses too perfect.

We sealed off every crack and we eliminated the very spaces house sparrows once used to nest in.

So what can we do about this?

There's lots of cheap and very cheerful actions we can take as individuals and as a society.

We can plant flowers and trees that support insect life.

We can provide nest boxes.

Let's bear house sparrows in mind when building and when developing.

We can avoid plastic grass, gravel and too much asphalt, ditch insecticides and yes, we can put up with the occasional mosquito bite.

But most importantly, let's talk about this issue.

Let's spread the word where you know you can make meaningful impact in schools, at work, in community groups.

Let's make this a conversation that grows and, in doing so, helps sparrow numbers to grow too.

These are all small but very powerful actions that can welcome house sparrows back into all of our lives.

Thank you to Dr.

Julia Schroeder, and thanks to our listeners who got in touch.

Do tell us us what you want us to find out next.

Our email address is insidescience at bbc.co.uk.

Lizzie Gibney and Mark Maslin are with me in the studio.

Did either of you identify the sparrow?

Are you good on your bike?

I thought it sounded familiar.

And I'm a little bit older than Liz, so yes, I remember what sparrows sound like.

Oh, tragic.

I know because I've got really into this app called Merlin.

Do you know this?

No.

Oh, it's so good.

I can recommend it on the BBC because it's free.

It's It's Cornell University's Bird App, and it just tells you what you're listening to.

And at the weekend, it found a tawny owl for me, so I'm quite pleased by that.

Wow.

Lizzie, I'm moving seamlessly from birds to quantum physics.

Weirdly, there is a link.

There is.

But it takes probably about half an hour to explain it, quantum biology.

Let's go back to the oddest ferry ride that I've been on, which took hundreds of physicists, including four Nobel Prize winners, to the windswept island of Heligoland.

Why?

Great question.

The reason why is there's a celebration going on this year of it being the centenary of quantum mechanics.

And something very special happened on Heligoland in 1925.

So Werner Heisenberg went there, 23-year-old physicists, and he came up with the maths that was the foundation of quantum mechanics.

Now, at that time, they knew about atoms and that there were electrons in orbits, but they weren't able to align predictions with their experiments and what he was able to do was come up with a way of just looking at what was observable looking at the leaps that the electrons made rather than the trajectories that they made and he he wrote that he had this epiphany and he went for a wander around the cliff tops and he sat and watched the sun rise and and and from there fell out the whole of quantum mechanics of course there was more work that went into it he had some colleagues that he worked with details details

when he got back you know to dry land but um if you want to have a party, you've got to have a date.

And the date is this year and this week on Heligoland.

So, what I love is: one, that he went to Heligoland to escape the terrible hay fever, which is just going to be my excuse.

Well, I could invent a new branch of physics, but you know, the hay fever just clogged my brain up.

And two, is that a hundred years on, people on this island were genuinely just still arguing about what quantum is.

Absolutely.

So, the mathematics works perfectly.

It's one of the most successful theories in all of science.

You know, it's behind MRI machines and lasers and even like transistors and just a regular computer, you know, harness quantum phenomena.

But that doesn't mean we actually understand what it means when we're talking about it in terms of reality.

We know what the experiments show, and we can make excellent predictions.

But if you get to Nobel Prize winners in a room and ask them, okay, but what is actually happening?

You know, does X cause Y?

Their answers are completely different.

And if you think that you don't understand quantum physics, maybe my documentary, What is Quantum?, which is airing on the 27th of August, will help.

Or at least it'll make you feel like you're not alone in not understanding.

Lizzie, you've also been looking through the week's science journals for us.

What from the incredible new research going on has grabbed your attention?

Okay, so I picked out, it's a paper in Science Advances, but it was written up in Nature by my colleague Davide Costovecki.

And it's looking at mysterious connection, correlation between Earth's magnetic field and the abundance of oxygen in the atmosphere.

Is this another angle for Mark to think about for

systems science?

So, what's the relation?

So, first of all, the way that they did it, I thought, was fascinating because they looked at, to get the oxygen levels, they looked at charcoal deposits because the wildfires that you have correlate with the amount of oxygen in the atmosphere.

So, by looking at charcoal deposits, they could get this oxygen record.

And then, the way that they figured out the magnetic field over the last 500 million years was by looking at lava.

So you have lava comes out and obviously it's flowing and there are little magnetic crystals and they align with magnetic field.

And by studying how they've kind of frozen out when the rock solidified, you can figure out the strength and the direction of the magnetic field at the time.

Oh, that's a good bit of, that's like the smashed watch giving you the time of the murder.

That's great.

Exactly, exactly.

They plotted these and saw that there does seem to be quite a strong correlation.

Now, the question, the big question that is still remaining is why.

So there is one and I have to say it's very speculative idea that perhaps having a stronger magnetic field, you know, it protects Earth's atmosphere from the solar wind, these charged particles that fired at us from the sun, and maybe that stops some leaching of oxygen.

So that is a potential connection.

But it's also possible that something, another completely distinct third thing is affecting both levels.

So one idea that was put forward by the researchers was that it could be a churning of the mantle, so you know, moving tectonic plates that could release a bunch of nutrients, which means algae flourish, which means oxygen is created, and at the same time has some kind of impact on the liquid core of Earth.

Finally, stress and sleep.

We all instinctively know that stress impacts sleep and other things like memory formation and memory ability.

This is a study that adds a little bit to our knowledge about how that actually happens in the brain.

So this was in the Journal of Neuroscience and Katie Kavanaugh at Nature wrote that up for us.

This was in mice, I should say.

They stressed them out, they had them in these little confined tubes and then the next day they did worse at memory tests and also they had disrupted sleep.

And then what the researchers in this paper did was they targeted what they thought was the pathway in the brain by which that happened and they could recreate the effect of stress.

They could also make the mice sleep worse and affect memory or they could dampen that down.

So they had the stress, but they dampened down this particular firing of neurons and then they didn't sleep quite as badly, and they had much better results on their memory tests.

And one thing that they found, which I don't think we knew about before, was that I think we thought that it might have been that stress impacts sleep, and bad sleep causes memory issues.

But actually, those things are independent.

Stress causes bad sleep, and stress also causes issues with memory function, which I take as maybe a tiny bit of a silver lining.

Like, I have tiny people who often wake me up a lot.

So, sometimes my sleep is very bad, but I can say, you know, my bad memory.

Does that make me feel better?

I don't know.

So, maybe getting back to some deep breathing that we did at the start of the programme would help?

It's very apt.

Finish on a deep breath.

Thank you, Lizzie Gibney from Nature and Mark Maslin from UCL.

I'm back next week with more of the science you need to know.

Bye for now.

You've been listening to BBC Inside Science with me, Marnie Chesterton.

The producers were Dan Welsh, Jonathan Blackwell, and Claire Salisbury.

Technical production by Rhys Morris, Sue Mayo, and and Ben Kesselman.

The show was produced in Cardiff by BBC Wales and West.

Suffs, the new musical has made Tony award-winning history on Broadway.

We demand to be hosted.

Winner, best score.

We demand to be seen.

Winner, best book.

We demand to be quality.

It's a theatrical masterpiece that's thrilling, inspiring, dazzlingly entertaining, and unquestionably the most emotionally stirring musical this season.

Suffs, Playing the Orpheum Theater October 22nd through November 9th.

Tickets at BroadwaySF.com