Two thousand year old moss in permafrost

While scientists are working on bringing extinct species like mammoths back to life, some things that we thought had gone for good may not be quite as dead as we had imagined. Peter Convey and his colleagues at the British Antarctic Survey examine ancient moss to study climate change, but were in for a surprise when, just like the film Gremlins, they simply added wate, as he explained to Kat Arney and Chris Smith...

Peter - Mosses give quite a good climate record and in parts of the Antarctic mosses have been growing in one place for several thousand years, up to 5,000 years is the oldest moss bank we know. And they're unusual in that mosses grow at the surface. They're green on top and each year they put on a few more millimetres of green growth. But the stem stays behind underneath them if you like. And ultimately, in the Antarctica, you'll get up to 2 or 3 meters thickness of moss and 20 centimetres down in this, it goes into permafrost because the Antarctic is very cold environment. And once it's in the permafrost, it's effective in stasis. We status cores from this moss banks because they tell us things about what the climate was like when the moss was actively growing hundreds or thousands of years ago, like that's our primary interest. But we looked at these moss cores and they actually looked very well preserved. The stems looked pretty well preserved, the leaves looked pretty well preserved, even if you go down to cellular level, the cell walls are intact. They don't look very damaged at all. So, we simply thought, how far down a moss core might it be possible for the moss to recover? We started out with, figuring the literature on the subject suggests a small number of decades. That's the sort of the time span the people have managed to get mosses to regrow from. But we got a core out that covered about 1600 years and we divided it into sections and put it in a plant growth incubator very simply. As you said, just added water and gave it some light. And lo and behold! We did get some shoots growing right through the depth of the core.

Kat - That must've been staggering when you sort of opened the lid, like crikey, it's gone green! How do you know that that's definitely those very, very old 1600 years for a plant to come back to life? How did you know it's definitely them?

Peter - It was surprising and pleasing, I must say. You have a feeling that's something is going to happen and it's nice when it does for once. If you looked in great detail, if you stick the core surface under the microscope and you look at the old shoots that were there, then the new shoot is growing, very definitely emerged from the older shoots. They were very firmly attached to them which wouldn't be the case if you got a sort of polluting spore in or a plant fragment in while we were drilling the core out. So, I think we're actually pretty confident that the new growth we're getting is from that depth, that age in the core. We're confident of the age. It's within radio carbon dating range. We're confident of the age because we've got plenty of very well preserved carbon based core material to get dates from.

Kat - So, these are mosses that were last green and leafy, around about the time of the end of the Roman Empire. It's fascinating that you can make them grow again, but is this little more than just, "Ooh! That's kind of cool!" What can it tell us?

Peter - To be fair, it was a blue sky question to start with, how long can things stay alive for? But having to discover they can stay alive, it tells us that if for instance you have an area of ground, an area of moss that's covered by ice, ice expands and contracts over century or millennial timescales. Then you have potential for surviving in the place where they are rather than being - we always used to think as ice comes forward, everything underneath it is wiped out. If that's not the case then biology survives or biodiversity survives where it is. The next time the ice retreats, you have potential for recolonizing the area so understanding the biodiversity of the area in a different way.

Kat - You mentioned that these mosses, they're 1600 years old and you said, "We thought they might be decades old." How does that compare to some of the other animals that we know that can kind of go into stasis and then be rehabilitated?

Peter - Well, it's sort of an open question. The ability to survive in these conditions is known as cryptobiosis, so the ability to survive long term freezing or long term drying out. And when you have an animal or a plant or even a microbial cell in that state, you or I can look at it and we can't do anything that tells us it's alive. We've sort of got to put it back in normal conditions and see if it gets up and walks away so to speak.

Now, there are a number of invertebrate animal groups best known are tardigrades and nematodes, but also some mites, some springtails, even some insects that can survive similar sorts of periods to what we thought mosses could survive, so 10, 20, 30 years, that sort of order. One thing we haven't done as yet with any of these cores is look to see whether there are any contained animals or any way that we can actually revive any contained animals within them. It's actually perfectly viable question. It's just we haven't had the chance to do it.

Kat - Jurassic Park for ants.

Peter - Yes, so much smaller. There's no dinosaurs in there.

Kat - This is fascinating. We talked on the show last week about taking humans to the Moon. If you could take maybe some plants in a dried static form, that would be quite useful if we were going to go and terraform or colonise other planets.

Peter - Well certainly, it's a way of carrying things in a sort of much lighter and much easier to maintain condition. I mean, it's sort of it's science fiction at the moment I guess. But we do know for instance that lichens, which are another sort of - they aren't plants. They're a symbiosis between algae and fungi, but they're very common in polar regions and extreme environments as well. We know that you can take either whole lichens or spores from lichens up onto the space station and they can survive space conditions. So yeah, potentially, these groups could play a role in, we would call it terraforming or at least providing oxygen into a space capsule environment.

Kat - Just very briefly, what would happen to the mosses that you've brought back to life if you then just planted them outside? Would they just be okay?

Peter - Basically, yes. I mean, they are polar species, so they are reasonably well-adapted to cold environments. But one of the species that we can do this or that we have in the Antarctic is actually a species that occurs up in the Arctic, it occurs in mountains in Scotland. I think a very close relative even occurs in Thetford Forest. So, in principle, you could actually sort of put it at least not in bright sunshine, but somewhere with reasonably cool, moist conditions and it would be quite happy here.

Kat - So, maybe one day, we might have George Church's woolly mammoths eating your rehabilitated moss.

Peter - We'd have to grow an awful lot of them, but yes.

Chris - Peter, have you done any genetic analysis on the moss to see if the stuff right at the bottom is similar to the stuff 1600 years younger right at the top?

Peter - The straight answer is no, but it is a question we're looking at. I mean, it's actually very interesting to see whether there have been any genetic or even physiological biochemical changes over that time because if the conditions were different 1600 years ago. You might expect different gene expression or different physiological adaptation to be there.

Chris - We interviewed a lady, quite a while ago now, but she found in an archaeological site some date pips that have been spat out by someone several thousand years ago in what's now Israel. And she was able to germinate them, and she got dates back from them, but she said the plants do look subtly different than the plants that grow now. And so it strikes me, your moss may have evolved as it's grown up its stem over those 2,000 years.

Peter - It's quite possible. It's a very fair approach to take. It's something we would like to - we are trying to do it.