when they felt the cold lack of fire in their lives.

他們因生活缺乏火而時感寒冷

But anthropologists theorize that early hominids

但人類學家推論

relied on lightning to cause forest fires,

原始人類依賴閃電引發森林大火

from which they could collect coals and burning sticks.

由此他們能收集木炭 和燃燒的樹枝

Fire gave them the ability to cook food and clear land,

火讓他們能夠煮食和清理土地

and became central in many rituals and traditions.

並成為很多儀式和傳統的中心

So instead of seeing forest fires as an exclusively bad thing,

所以古代人類 並不完全視森林大火為壞事

ancient humans may have learned to appreciate them.

且可能已知道要感謝它們

Yet, it wasn't just humans who benefitted from these natural phenomena.

但並不只是人類受益於這種自然現象

Even as they destroy trees, fires also help the forest themselves,

即使大火燒毀樹木， 但同時也幫助森林本身

however counterintuitive that seems.

這看來悖於常理

In fact, several forest species, such as select conifers,

事實上，許多森林樹種── 如高等的針葉樹── 需要火來生存

need fire to survive.

但火如何既毀滅生命，又創造生命？

But how can fire possibly create life in addition to destroying it?

答案在於這些森林的成長方式

The answer lies in the way that certain forests grow.

在北美洲西部的針葉樹林

In the conifer-rich forests of western North America,

美國黑松總設法尋求陽光

lodgepole pines constantly seek the Sun.

它們的種子偏好生長於 空曠多陽的土地

Their seeds prefer to grow on open sunny ground,

幼樹互相競爭 試圖掙得更多陽光

which pits saplings against each other as each tries to get more light

要比旁邊的樹 生長得更筆直、更迅速

by growing straighter and faster than its neighbors.

經年累月，一代代細長高聳的美國黑松

Over time, generations of slender, lofty lodgepoles

形成傘狀樹冠， 遮蔽下面的「地面層 (forest floor)」

form an umbrella-like canopy that shades the forest floor below.

但當這些樹木的球果成熟， 釋放它們隨風旋轉的種子

But as the trees' pine cones mature to release their twirling seeds,

這預示了美國黑松將面對一個問題

this signals a problem for the lodgepoles' future.

只有少數種子能在高聳 母樹下的陰涼地方發芽

Very few of these seeds will germinate in the cool, sunless shade

為適應這問題， 這些樹木生長出兩種球果

created by their towering parents.

一種是一般的年生球果， 會自發釋放種子

These trees have adapted to this problem by growing two types of cones.

而另一種是「晚熟球果」

There are the regular annual cones that release seeds spontaneously,

需要環境誘因來釋放種子

and another type called serotinous cones,

樹木生長出數以千計的晚熟球果

which need an environmental trigger to free their seeds.

它們被樹脂封實， 如同防水的時空膠囊

Serotinous cones are produced in thousands,

多數能夠留在樹上數十年，不受破壞

and are like waterproofed time capsules sealed with resinous pitch.

這種球果掉落地上後， 也可獨立存活數年

Many are able to stay undamaged on the tree for decades.

而當温度夠高，這些球果便會裂開

Cones that fall to the ground can be viable for several years, as well.

讓我們看看實際發生情況

But when temperatures get high enough, the cones pop open.

當一場針葉林大火開始

Let's see that in action.

通常會如此蔓延開來

Once it's gotten started, a coniferous forest fire

火焰燒毀茂密的「灌木層 (understory)」， 當中包括花旗松

typically spreads something like this.

花旗松耐蔭， 能在美國黑松的樹冠下生長

Flames ravage the thick understory provided by species like douglas fir,

大火利用這些小樹作階梯

a shade-tolerant tree that's able to thrive

向上蔓延至以老美國黑松為主的 「樹冠層 (canopy)」

under the canopy of lodgepole pines.

引燃巨大的樹冠火

The fire uses these smaller trees as a step ladder

火場温度高達華氏 2400 度

to reach the higher canopy of old lodgepole pines.

這遠遠高於華氏115-140 度

That ignites a tremendous crown fire

即晚熟球果種子 能被釋放的所需温度

reaching temperatures of up to 2400 degrees Fahrenheit.

達到那些温度時，球果裂開

That's well more than the 115-140 degrees

釋放出數以百萬的種子

that signal the moment when serotinous seeds can be freed.

種子隨熱空氣而飄散，形成新的森林

At those temperatures, the cones burst open,

大火之後，富含碳的泥土 及空曠多陽的地形

releasing millions of seeds,

促使滿地的美國黑松種子 迅速發芽生長

which are carried by the hot air to form new forests.

老森林的死亡帶來新森林的誕生

After the fire, carbon-rich soils and an open sunlit landscape

火對於整個 更廣泛的生態系統也很重要

help lodgepole seeds germinate quickly and sprout in abundance.

沒有森林大火來更新樹木， 主要樹木品種便會消失

>From the death of the old forest comes the birth of the new.

很多依靠這些樹木的生物亦會消失

Fires are also important for the wider ecosystem as a whole.

而如果一個依賴火的森林 太久沒有被燃燒

Without wildfires to rejuvenate trees, key forest species would disappear,

會提高災難性大火的風險

and so would the many creatures that depend on them.

火災足以燒毀整個森林

And if a fire-dependent forest goes too long without burning,

更不要說人類的居所和生命

that raises the risk of a catastrophic blaze,

這正是為何森林管理員 有時故意進行可控制的火燒

which could destroy a forest completely,

藉此減少可燃物， 避免更危險的森林大火

not to mention people's homes and lives.

森林大火或許是駭人的自然破壞

That's why forest rangers sometimes intentionally start controlled burns

但它們對於維持北方針葉林的 健康生態系統必不可少

to reduce fuels in order to keep the more dangerous wildfires at bay.

接受這樣的事實

They may be frightening and destructive forces of nature,

我們可保護自己， 免於它們進一步的傷害

but wildfires are also vital

同時讓森林如同傳說中的鳳凰

to the existence of healthy boreal forest ecosystems.

從自身的灰燼中，浴火重生

By coming to terms with that,

翻譯：Crystal Yip

we can protect ourselves from their more damaging effects

while enabling the forests, like the legendary phoenix,

to rise reborn from their own ashes.