森林起火引发北方气候谜团(下)

I think that I would have anticipated something like twice as fast, not necessarily four times as fast.

我想我应该能预期到两倍的速度，而不是四倍。

And the reason that this number is really interesting, this increase in rate or are so remarkable to us is that prior to this point,

这个数字很有趣的原因是，这个速率的增加对我们来说很显著，因为在这之前，

we always assumed that the stands that burned severely were a net source of carbon to the atmosphere,

我们一直认为，燃烧严重的树丛是大气中碳的净来源地，

meaning they lost more carbon in the fire than they could hope to reaccumulate before the next fire came through.

这意味着它们在大火中失去的碳比它们希望在下一次火灾发生前重新积累的碳要多。

Ecologists like Johnstone have worried for years about the amount of carbon that could be lost to the atmosphere from wildfire in the boreal forest, because that could lead to what she calls a “runaway feedback loop with climate change.”

多年来，像约翰斯通这样的生态学家一直担心北方森林野火可能会导致大量碳流失到大气中，因为这可能会导致她所说的“气候变化的失控反馈循环”。

And so this example of more rapid accumulation of carbon in deciduous broadleaf stands is a way of thinking of putting the brakes on the runaway train.

所以落叶阔叶林碳积累更快是一种给失控的列车踩刹车的方式。

And it's really valuable to recognize that by changing that type of vegetation that recovers after fire or we actually change the carbon accumulation rate.

认识到通过改变火灾后恢复的植被类型或者实际上改变了碳的积累速率是很有价值的。

Johnsone says the change in vegetation regime might help bring the system back into “control”—at least for a bit.

约翰森表示，植被状况的改变可能有助于使整个生态系统恢复“控制”——至少在一定程度上是这样。

There are limits to this seeming self-regulation.

这种看似自动调节的做法有其局限性。

So let's change the metaphor to driving a bus down the highway.

所以让我们把这个比喻改成在高速公路上开巴士。

And what we're concerned about is that as far as climate warming leads to more fire weather, we get more severe and active fires burning in the boreal forest that releases more carbon.

我们担心的是，只要气候变暖导致更多的火灾天气，北方森林的火灾就会更严重、更活跃，从而释放更多的碳。

And that's just pushing the accelerator pedal down on this bus.

这只是把这辆巴士的油门踩下去。

The added carbon accumulation, as the forest regime regenerates and shifts from coniferous to deciduous trees—that’s like putting the parking brake on while driving the bus, says Johnstone.

约翰斯通表示，随着森林环境更新，针叶树转变到阔叶树，增加的碳积累就像在驾驶公共汽车时踩刹车一样。

So, you're slowing down that acceleration, but it's not enough to stop it completely.

所以，你减慢了加速度，但这不足以让它完全停止。

And as long as we are continuing to pump carbon into the atmosphere.

只要我们继续向大气中排放碳。

Particularly through our own fossil fuel combustion, then we're going to keep accelerating.

特别是我们自己的化石燃料燃烧，我们将继续加速这一进程。

But this feedback of vegetation change in the boreal forest is at least pushing back against that acceleration to slow us down.

但这种北方森林植被变化的反馈至少会把加速的速度往回推，让我们减速。

And we need to use all the tools available to us to help slow that bus down because it's headed to go over a cliff.

我们需要使用所有可用的工具来减缓那辆巴士的速度因为它正朝着悬崖驶去。

Discovering this natural shift took some sleuthing.

需要一些侦查才能发现这种自然的转变。

Well, this research really played out like a detective novel.

这项研究的逐步开展就像一部侦探小说。

At first we noticed, oh, the fires seem to be doing different things and asking questions about, well, if the fire, the way the fire burns changes, how does that change the forest regeneration?

一开始，我们注意到，哦，火灾似乎是重要的事情，并提出了一些问题：如果火灾，大火燃烧的方式发生了变化，这将如何改变森林再生?

And that required a bunch of experiments and following patterns of forest regeneration for five, 10,15 years.

这需要大量的实验，跟踪5年，10年，15年森林更新的模式。

Deciduous trees like birch and aspen live for about 100 years, so the team couldn’t simply wait for one or two centuries to find out what happens in the forest.

像桦树和白杨这样的阔叶树的寿命约为100年，所以研究小组不能只是等上一两个世纪来发现森林里发生了什么。

So we went out and found all these different age stands across the boreal forest in Alaska and sampled them and tried to make sure that we had a good comparative set of ages that could be linked together as being probably starting from the same initial conditions and then just have different ages.

所以我们去了阿拉斯加的北方森林，发现了这些不同年代的树木, 我们对它们进行了抽样，并试图确保我们有一个可以把树木年龄联系在一起的很好的年龄对比集合，因为这些树木可能从相同的初始条件开始生长，然后有着不同的年龄。

And that piecing together is like doing a jigsaw puzzle.

这种组合资料就像做拼图游戏。

The pieces of the puzzle that are still missing are the ones that help explain how we pump the brakes before that bus reaches the cliff.

目前仍未解开的谜题是那些有助于解释我们如何在巴士到达悬崖前刹住车的谜题。

For Scientific American, I’m Emily Schwing.

我是《科学美国人》的艾米丽·施温。