Levende Wolken

Levende Wolken
VPRO Noorderlicht / 25 min / 06-12-1998
Onderzoekers zoals evolutie-expert Prof Bill Hamilton en Dr. Tim Lenton beginnen te vermoeden dat micro-organismen zoals bacterieën en algen een grote rol spelen bij de vorming van wolken. Dat levende organismen invloed zouden hebben op de atmosfeer werd begin jaren zeventig voor het eerst geopperd door James Lovelock in zijn Gaia-theorie. De theorie van Lenton en Hamilton lijkt de eerste bevesting van Lovelocks ideeën.

tekst van de uitzending:

VPRO NOORDERLICHT – TRANSCRIPT
AFLEVERING “LEVENDE WOLKEN”
DOOR JOS WASSINK
UITZENDING 06 DECEMBER 1998

DR JAMES LOVELOCK,
AUTEUR GAIA-THEORIE:
If there were no algae in the oceans, there would be very little other sealife at all. But not only that, the Earth would be enormously hotter than it is now. Perhaps 10 or even 20 degrees Celsius hotter than the climate we have at present.

PROF. BILL HAMILTON
ZOOLOGY, UNIVERSITY OF OXFORD:
Oh, it is a very good place to do clouds natural history, there are very nice selections of cumulus clouds here, and you can see various things are going on and most of it just physics, but there may be some biology in it and that’s of course what’s interest me.

COMMENTAAR:
Op school wordt verteld dat water verdampt, opstijgt, condenseert tot wolken en weer neerdaalt als regen. Natuurkunde van het vrije veld. Maar er is meer aan de hand. Onderzoekers beginnen te vermoeden dat micro-organismen zoals bacterieën en algen een grote rol spelen in de vorming van wolken.

TITEL LEVENDE WOLKEN

COMMENTAAR:
Dat levende organismen invloed zouden hebben op de atmosfeer werd begin jaren zeventig voor het eerst geopperd door James Lovelock in zijn Gaia-theorie.

DR JAMES LOVELOCK:
The best way to understand what Gaia is is to think of it as a giant planetary thing, rather with the properties of a living organism, but nowhere near as complicated as a living organism.

DR TIM LENTON,
GAIA-DESKUNDIGE:
The essence of Gaia theory is that the Earth is a self-regulating system in which life has a key role to play in regulating it’s planetary environment.

COMMENTAAR:
Tim Lenton promoveerde onlangs op de moeizame verhouding tussen Lovelock’s Gaia theorie en de evolutieleer. In de afgelopen jaren ontwikkelde hij een intensieve samenwerking en vriendschap met Lovelock.

DR TIM LENTON:
I read Jim Lovelock’s books and was immediately captivated by the idea. And then, when I went to university to study natural sciences, I began to realise that the GAIA theory was what I really wanted to do some research on in the future.

COMMENTAAR:
Lentons keuze voor de Gaia-theorie was opmerkelijk omdat Gaia in wetenschappelijke kringen weinig serieus genomen werd. Veel wetenschappers ergerden zich aan het idee van een regulerend bewustzijn dat aan de theorie ten grondslag leek te liggen.

DR TIM LENTON:
Historically speaking there has been quite a lively and controversial debate. And I would say that in past evolutionary biologists have been some of the most incisive critics of Gaia theory because they couldn’t see how on Earth organisms could be contributing to regulating their planetary environment in a way that would pay, that would make sense in natural selection.

COMMENTAAR:
In de jaren zeventig ondernam James Lovelock een zeereis van Engeland naar Antartica. Hij stond onder druk om met voorbeelden te komen van organismen die een regulerende invloed uitoefenden op hun omgeving.
Zijn aandacht was getrokken door het gas dimethylsulfide oftewel DMS dat door algen geproduceerd wordt. Tijdens de reis mat hij overal de concentraties van DMS boven zee en van algen in het water.

DR JAMES LOVELOCK:
Algae produce a gas called dimethylsulphide which goes up into the atmosphere. It’s quite an unconscious thing, they don’t do it on purpose, but nevertheless it happens and this gas when it oxidises in the atmosphere is the source of the tiny droplets that flow in the air around which clouds form.

WOLKEN CONDENSEREN

COMMENTAAR:
Lovelock had het mechanisme ontdekt van hoe algen wolken maken. Daarmee verschoof de vraag naar waarom ze dat doen. Wat voor baat heeft een alg bij het veroorzaken van een wolk?

DR JAMES LOVELOCK:
Of course the benefit for the algae for doing this is that the clouds tend to keep the Earth cooler. Without the clouds the Earth would be 10 to 20 degrees hotter than it is today and dreadfully uncomfortable not only for us but for the algae in the ocean.

COMMENTAAR:
Volgens Lovelock zouden algen dus wolken produceren om de Aarde koel te houden. Evolutie-expert Bill Hamilton uit Oxford las Lovelock’s verklaring, maar was er niet van onder de indruk

PROF. BILL HAMILTON:
A evolutionist immediately asks: why the hell should these algae in the sea be producing clouds which are going to benefit the lands and benefit everyone else, in act benefit much more organisms as they benefit themselves?

COMMENTAAR:
Tim Lenton, die milieuwetenschappen studeerde aan de universiteit van Norwich, begon zich te realiseren waar de schoen wrong tussen Gaia en evolutie.

DR TIM LENTON:
We can see that the Earth shows some remarkable properties of regulation and that organisms are clearly involved in this, but we have the challenge to sort of rationalize that in terms, which make sense to the individual organisms.

COMMENTAAR:
Om na te gaan of selectie op individueel niveau klimaatregeling tot gevolg kon hebben, ontwierp Lovelock het computermodel Daisyworld. Hierin compenseren zwarte en witte madeliefjes de invloed van de toenemende zonnestraling. Zwarte madeliefjes nemen de zonnewarmte op, witte daarentegen weerkaatsen het grootste deel.

DR TIM LENTON:
When conditions get warm enough, as the Sun is warming, daisy seeds begin to germinate. Than the black daisies by virtue of their colors will start to warm themselves up, this increases their spread, and as they spread, they darken the planet and they take the temperature from 5 degrees to something more like 25 degrees on the planet surface.
Now if we are beginning to force the system by warming the Sun further, things start to be too hot around the equator, and the white daisy seeds begin to germinate and the white daisies are beginning to take over.
Now this has a counterbalancing effect. As the white daisies start to cool the planet, to counteract the warming Sun, and this can go on for great length of time, with the warmer the Sun gets, the more the white daisies take over from the black daisies. Until eventually we will be left with a planet that’s covered only with white daisies, as the dark daisies are squeezed out from the poles.
Until eventually we are going to be left with a white planet, a planet of white daisies, and if one warms the Sun even further, eventually they will die off. To begin with at the equator, but as the daisies disappear, the planet darkens very rapidly, and they will all disappear as things warm up in a kind of positive feedback. And that’s the end of life on Daisy World.

PROF. BILL HAMILTON:
Daisyworld, I am afraid I am not enthusiastic about because it is set up in a way that almost bound to produce the effect desired. The basic trouble is that daisies benefit themselves as they benefit the planet and given that there is really no problem, what we have think of something is some other kind of organism that benefits itself in the same time as it harms the planet.

COMMENTAAR:
Dit had het einde kunnen zijn van het verhaal.
Maar Lovelock besloot de confrontatie met Hamilton aan te gaan.

DR JAMES LOVELOCK:
It so happens that I’m a visting fellow at one of the Oxford colleges, and when I was there I called up Bill Hamilton and we arranged to meet in the evening. And spent a very pleasant evening arguing together and finishing up by saying oh, well that’s your view of it and this is my view of it and we’ll have to agree to differ.

PROF. BILL HAMILTON:
It was almost an argument. I was not very happy with his Daisyworld and various other things. And eventually we agreed to differ, but he said: could I suggest that I send a student that I know to send you a copy of a manuscript that he is working on for review of all these various phenomena, including some of which we haven’t discussed.
And I said yes and a week or so later I received an early draft of the article, which Tim Lenton has now published in the journal Nature.

DR TIM LENTON
So Jim sort of put the two of us in touch, in that he suggested that I write to Bill Hamilton and I sent Bill a copy of an article I’ve written on Gaia and natural selection. And I guess we took it from there.

COMMENTAAR:
Tim Lentons artikel in NATURE ging over de vraag hoe zelf-regulering op planetair niveau kan ontstaan uit natuurlijke selectie op individueel niveau.

PROF. BILL HAMILTON:
I read it through and I immediately appreciated that this was a better account of Gaia from an evolutionist’s point of view that I have seen before.
To my mind there were then and still are some big holes to be filled but still at least it was taking notice of evolutionary theory as we know it.

DR TIM LENTON:
And he was very complementary when he wrote back.
And than a little bit later on, I think something that I had written about plankton producing this gas – DMS – had got him thinking.

PROF. BILL HAMILTON:
I noticed a word in Tim Lenton’s account, which was the word antifreeze. He said that probably there was an original purpose, which wasn’t cloud building, it was prevention of freezing. And for most part he had been talking about algae which had been sampled in the tropical oceans and so on so I thought: why the hell to produce antifreeze in the middle of tropical ocean. Then I thought waterspouts, and I thought that occasionally these organisms were sent up high up onto the atmosphere, in some kind of a thunderstorm or a waterspout, and there they might really need antifreeze.

PROF. BILL HAMILTON:
And this gave me the idea, that almost anywhere in the ocean wherever there are cumulus clouds forming above, the algae could be getting themselves a ride if only they could get themselves out of the sea surface. There will be winds that will be converging and going up to form the basis of fluffy cumulus clouds.

COMMENTAAR:
Het bijzondere aan Hamilton en Lentons idee is dat het eerst verklaart wat voor baat algen zouden hebben bij het veroorzaken van wolken. Namelijk verspreiding.

PROF. BILL HAMILTON:
It’s difficult at first to imagine that just jumping out from the sea and popping down somewhere else is going to help you, and you tend to think that the sea is a very uniform habitat, but it does help you, even if it is a uniform habitat. This is a very important point of the theory.

DR JAMES LOVELOCK:
I’ve always felt that the establishment of Gaia as a truebill would depend on finding the links, and they’re are going to be many and subtle, between the organisms and the big system of the climate and the chemistry and I see this story of spora and Gaia as one of those first links. So it’s most important that this should be established, for Gaia that is.

COMMENTAAR:
Het zou allemaal heel mooi zijn, maar tot nu toe is het verhaal van Hamilton en Lenton pure theorie. Wat ontbreekt is het bewijs dat algen inderdaad in de lucht voorkomen.
Als eerste stap wilde Hamilton weten of algen zich inderdaad los kunnen maken uit het zeewater. Hij nam daarvoor contact op met veldbioloog Chad Marshall die veel ervaring heeft men luchtbemonsteringen.

DR WILLIAM (CHAD) MARSHALL,
LUCHTBIOLOOG, MARINE BIOLOGICAL ASSOCIATION:
I was working in Antartica and even in Antartica, one of the most pristine environments in the world, you’re still able to grow micro-organisms that you catch out of the air. So what we’re looking for is algae ejecting themselves into the air and being taken into the air and acting as cloud condensation nuclei. This is all part of Bill’s hypothesis for a driving mechanism behind Gaia.
We have a rotarod sampler which spins round two rods and they collect the particles through impaction, very much like if you imagine you drive your car along the road, very fast and on the end of the day you might have lots of flies on your windscreen and this is how these samplers work. Only they’re working on collecting much smaller particles, so the leading edges on which the particles are colecting are a lot smaller than a car, obviously.
A day like today it’s very windy, we’ve got lot of white caps. Any organism that’s in the water column are going to be injected into the air column through bubbleburst porcesses and splashing and it’s very fine aerosoles that get injected into the air and the organisms are held within a droplet and the droplet might evaporate away very very quickly, it’s just a couple of micron’s across. Then you have an aerosole of micro-organisms and we’re hoping to catch that.

COMMENTAAR:
De monsters worden onderzocht in het laboratorium van de Marine Biological Association in Plymouth. Het laboratorium heeft een speciale koelcel ingericht voor het kweken van algen.

DR CHAD MARSHALL
(IN CULTURE ROOM:)
Okay, today’s collection we’re gone put in here. And hopefully these lights will encourage some algae to grow. And we can see these are collections that we made eight, nine weeks ago and in there you can see the strip with there’s some funghi growing in there, we’re not particularly interested in the funghi, this shows there’s stuff living in the air of course but… what we’re mainly interested in is .. the algae. The green stuff in there, there’s funghias well in there, but this shows quite clearly that we’ve got algae that we’ve collected and that we’ve observed under the microscope on the strips and this tells us that those algae are viable and they can grow.

DR. CHAD MARSHAL
(ACHTER CONFOCAL MICROSCOPE)
Here we’ve got some pictures that are taken from the strips from the rotarod samplers that we’ve made into slides. These round blobs here are actual algal cells, they are each about 5 microns across each cell. There, there, there. Generally when I’m looking through the sample, we scan using ultraviolet light so I can pick out the cells, cause there’s not many compared to the other material here. In this instance we see bright blobs against a dark background and these blobs are chloroplasts, the photosynthetic part of the algae, which fluoresce back when they are excited with ultraviolet light, high-energy light.

COMMENTAAR:
Enkele meters boven zee blijken dus groene algen in de lucht te zweven. Dat is goed nieuws, maar hoe zit het met algen in de wolken?

PROF. BILL HAMILTON:
There has been a lot of collection of fungal spores, bacteria and algae in the clouds, but as yet the ones that are the most famous for DMS production have not been recorded from clouds.
And I would like very much to get up in an airplane with an appropriate collecting apparatus hopefully with someone who knows how to handle that apparatus to try to prove that they are there.

COMMENTAAR:
De onderzoekers slaagden er niet in zo’n monstering in de wolken tot stand te brengen. Tenslotte besloot Noorderlicht zelf maar de proef op de som te nemen.

JOS WASSINK:
We huurden een vliegtuig en vlogen naar Schiermonnikoog. Boven de Waddenzee namen we een luchtmonster op een manier die in de jaren vijftig nog gebruikelijk was.
Na tien minuten werd het petrischaaltje luchtdicht afgesloten en zes weken later bij ons tweede bezoek aan het laboratorium in Plymouth onderzocht.

DR CHAD MARSHALL:
You definetely got something growing.
– It’s smelly isn’t it?
It is yes, you definetely got some funghi. They’ve probably got producing spores so that we can look at those under the microscope and see what you’ve got. We’re about to identify those probably without too much of a problem.
We’ve got some fungal spores here. And a few what I think are pollen grains but it’s quite hard to tell, there’s definitely fungal spores. Massal fungal fibers there, you can see the chains of spora there.

DR CHAD MARSHALL
(THROUGH MICROSCOPE)
– No algae? – No algae in there at all, no. If there had been algae trapped on these plates, that you’ve exposed they would have been very very quickly overgrown by this mass here. This mass of funghi and bacteria and it wouldn’t really have had a chance to grow.

JOS WASSINK:
OK, so we underestimated the problem a bit of catching algae in the air.

DR CHAD MARSHALL:
I think you did, but it was a nice try and it demonstrates you know, we’ve caught our funghi and there’s living organisms in the air.

COMMENTAAR:
Ons is het niet gelukt om algen aan te tonen in wolken. Nu zegt dat niet zoveel, want bij nader inzien bleken de door ons onderzochte wolken niet boven zee, maar boven land ontstaan te zijn. Of zoals Chad zei: leuk geprobeerd, maar ieder z’n vak.

COMMENTAAR:
Inmiddels heeft de samenwerking tussen Hamilton en Lenton er wel toe geleid dat biologen de Gaia-theorie serieus beginnen te nemen.

PROF. BILL HAMILTON:
My opinion on the Gaia theory generally got more favorable as it rolled by. At first I just didn’t see how it could work. However right from the beginning there’s examples of feedback mechanisms that seemed to be stabilizing and beneficial to life generally were quite impressive and I have to say that over the years they got more and more impressive, and till now I think we have to recognize at least that there is a phenomena that needs to be explained.

DR TIM LENTON:
I think Gaia theory has a great deal to offer to evolutionary
theory, because sometimes what an organism does, changes the environment in a way that then feeds back on the growth rate of that organism or even on the forces of the natural selection operating on that organism. And that would add something to conventional evolutionary theory, which has never really explicitly thought of that link. It has only dealt with individuals interacting with one another, not this kind of feedback to the whole system.

DR JAMES LOVELOCK:
I should say that I’ve reached a time in life when trying to keep up with the complexities of Gaia is getting too much for me and I thought it was high time that someone younger like Tim took on the task and he’s done so admirably.

© Het Inzicht / Jos Wassink, 1998

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