Nature Podcast：南极的雨林

又到了每周一次的 Nature Podcast 时间了！欢迎收听本周由Benjamin Thompson和 Nick Howe 带来的一周科学故事，本期播客片段讨论9000万年前的南极雨林。欢迎前往iTunes或你喜欢的其他播客平台下载完整版，随时随地收听一周科研新鲜事。

音频文本：

Host: Shamini Bundell

Next up on the show, we’re travelling south… far south to latitudes near to the South Pole. It’s a pretty cold and icy place right now, but it wasn’t always that way. This week in Nature, a team of researchers have been finding out about the very different climate and ecology that was there in the Cretaceous period about 90 million years ago. Reporter Dan Fox called up Johann Klages, who led the research, and started by asking him exactly where this research was done?

Interviewee: Johann Klages

Where we work is currently the most rapidly changing part of the Antarctic Ice Sheet. The glaciers are retreating at an accelerating pace. We took a drilling device, a seafloor drilling device, that allowed us to drill deeper and to also, at the same time, go deeper in time and see into time frames of Antarctica that looked completely different than what we see today.

Interviewer: Dan Fox

And what did you find when you dug deeper?

Interviewee: Johann Klages

We drilled into completely different stuff which was full of fossil roots, of very fine material bearing diverse taxa of pollen and spores, and we knew we had something very special.

Interviewer: Dan Fox

So, what do these pollen and spores reveal about the environment during this period?

Interviewee: Johann Klages

It must have been an environment like a swampy, temperate rainforest environment. Antarctica was much warmer than we knew before and than we expected. Today, the latitude of the drill location is about 73 degrees south, but 90 million years ago it was 82 degrees south, which means that it’s only 900 kilometres away from the South Pole. And we had a mean annual temperature of 13 degrees Celsius, which is warmer than the annual mean temperature of Germany right now, and we had summer temperatures of around of 20 degrees Celsius in the air but also in the surface water.

Interviewer: Dan Fox

So, what sort of things could have been living in this swampy rainforest?

Interviewee: Johann Klages

It was a diverse environment, full of plants and you have to assume that in this kind of environment you had, of course, dinosaurs, you had insects because we also have the pollen record of the first flowering plants that far south. So, no one knew before that flowering plants went so far south.

Interviewer: Dan Fox

And so, just to get a kind of real image of this rainforest – ignoring the dinosaurs, obviously – was there somewhere on Earth right now that would be of a similar appearance or makeup?

Interviewee: Johann Klages

I think the closest environment you would look at would be the South Island of New Zealand and on the South Island to the north-western part. There you have pretty coastal, near-temperate rainforests. But we have to emphasise this – we don’t really have a modern analogue for what we found because if you look at latitudes of 80-82 degrees north or south right now, it’s pretty icy.

Interviewer: Dan Fox

Yeah, and one other thing I know about the polar regions is that they’re dark for a lot of the year, so how do you think this kind of verdant ecology survived in those conditions?

Interviewee: Johann Klages

One of the main drivers is CO2, and CO2 not in concentrations we see right now from just about, let’s say, what do we have right now, 400-410 ppm. No, you need something around 1,200-1,700 ppm CO2 in the atmosphere to get something like that.

Interviewer: Dan Fox

And my last question is with global warming, are we likely to see this sort of vegetation at the South Pole again any time soon?

Interviewee: Johann Klages

We have to keep in mind that the plate tectonic or configuration at the time was completely different than it is today, but at the same time, we do also everything to emit a lot of CO2 in the atmosphere, and what we showed is that excessive amounts of CO2 can be very powerful. I could imagine that we get close to CO2 levels where things will get pretty interesting, but to get a similar environment close to the South Pole like we reconstructed now, I think this is pretty unlikely. But at the same time, it shows us this already happened on the planet. We had that already. This is not fiction. This happened. It makes us aware of how fragile and flexible our planet is, and of what can happen when things go out of control.

Host: Shamini Bundell

That was Johann Klages of the Alfred-Wegener-Institut in Bremerhaven, Germany. 

相关论文：

《自然》论文：Temperate rainforests near the South Pole during peak Cretaceous warmth

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