There was a time before our ancestors smashed flint and steel together, when they felt the cold lack of fire in their lives.
很久以前，我们的祖先还未将燧石和铁器互击，他们因生活缺乏火而时感寒冷。
But anthropologists theorize that early hominids relied on lightning to cause forest fires,
但人类学家推论原始人类依赖闪电引发森林大火，
from which they could collect coals and burning sticks.
由此他们能收集木炭和燃烧的树枝。
Fire gave them the ability to cook food and clear land, and became central in many rituals and traditions.
火让他们能够煮食和清理土地，并成为很多仪式和传统的中心。
So instead of seeing forest fires as an exclusively bad thing, ancient humans may have learned to appreciate them.
所以古代人类并不完全视森林大火为坏事，且可能已知道要感谢它们。
Yet, it wasn't just humans who benefitted from these natural phenomena.
但并不只是人类受益于这种自然现象。
Even as they destroy trees, fires also help the forest themselves, however counterintuitive that seems.
即使大火烧毁树木，但同时也帮助森林本身，这看来悖于常理。
In fact, several forest species, such as select conifers, need fire to survive.
事实上，许多森林树种，如高等的针叶树，都需要火来生存。
But how can fire possibly create life in addition to destroying it?
但火如何既毁灭生命，又创造生命？
The answer lies in the way that certain forests grow.
答案在于这些森林的成长方式。
In the conifer-rich forests of western North America, lodgepole pines constantly seek the Sun.
在北美洲西部的针叶树林，美国黑松总设法寻求阳光。
Their seeds prefer to grow on open sunny ground,
它们的种子偏好生长于空旷多阳的土地，
which pits saplings against each other as each tries to get more light by growing straighter and faster than its neighbors.
幼树互相竞争，试图挣得更多阳光，要比旁边的树生长得更笔直、更迅速。
Over time, generations of slender, lofty lodgepoles form an umbrella-like canopy that shades the forest floor below.
经年累月，一代代细长高耸的美国黑松形成伞状树冠，遮蔽下面的地面层。
But as the trees' pine cones mature to release their twirling seeds, this signals a problem for the lodgepoles' future.
但当这些树木的球果成熟，释放它们随风旋转的种子，这预示了美国黑松将面对一个问题。
Very few of these seeds will germintate in the cool, sunless shade created by their towering parents.
只有少数种子能在高耸母树下的阴凉地方发芽。
These trees have adapted to this problem by growing two types of cones.
为适应这问题，这些树木生长出两种球果。
There are the regular annual cones that release seeds spontaneously,
一种是一般的年生球果，会自发释放种子
and another type called serotinous cones, which need an environmental trigger to free their seeds.
而另一种是晚熟球果，需要环境诱因来释放种子。
Serotinous cones are produced in thousands, and are like waterproofed time capsules sealed with resinous pitch.
树木生长出数以千计的晚熟球果，它们被树脂封实，如同防水的时空胶囊。

Many are able to stay undamaged on the tree for decades.
多数能够留在树上数十年，不受破坏。
Cones that fall to the ground can be viable for several years, as well.
这种球果掉落地上后，也可独立存活数年。
But when temperatures get high enough, the cones pop open.
而当温度够高，这些球果便会裂开。
Let's see that in action.
让我们看看实际发生情况。
Once it's gotten started, a coniferous forest fire typically spreads something like this.
当一场针叶林大火开始，通常会如此蔓延开来。
Flames ravage the thick understory provided by species like douglas fir,
火焰烧毁茂密的灌木层，当中包括花旗松
a shade-tolerant tree that's able to thrive under the canopy of lodgepole pines.
花旗松耐荫，能在美国黑松的树冠下生长。
The fire uses these smaller trees as a step ladder to reach the higher canopy of old lodgepole pines.
大火利用这些小树，作阶梯向上蔓延至以老美国黑松为主的树冠层。
That ignites a tremendous crown fire reaching temperatures of up to 2400 degrees Fahrenheit.
引燃巨大的树冠火，火场温度高达华氏2400度。
That's well more than the 115-140 degrees that signal the moment when serotinous seeds can be freed.
这远远高于华氏115-140度，即晚熟球果种子能被释放的所需温度。
At those temperatures, the cones burst open, releasing millions of seeds, which are carried by the hot air to form new forests.
达到那些温度时，球果裂开，释放出数以百万的种子种子，随热空气而飘散，形成新的森林。
After the fire, carbon-rich soils and an open sunlit landscape help lodgepole seeds germinate quickly and sprout in abundance.
大火之后，富含碳的泥土及空旷多阳的地形，促使满地的美国黑松种子迅速发芽生长。
From the death of the old forest comes the birth of the new.
老森林的死亡带来新森林的诞生。
Fires are also important for the wider ecosystem as a whole.
火对于整个更广泛的生态系统也很重要。
Without wildfires to rejuvenate trees, key forest species would disappear, and so would the many creatures that depend on them.
没有森林大火来更新树木，主要树木品种便会消失，很多依靠这些树木的生物亦会消失。
And if a fire-dependent forest goes too long without burning, that raises the risk of a catastrophic blaze,
而如果一个依赖火的森林，太久没有被燃烧，会提高灾难性大火的风险
which could destroy a forest completely, not to mention people's homes and lives.
火灾足以烧毁整个森林，更不要说人类的居所和生命。
That's why forest rangers sometimes intentionally start controlled burns to reduce fuels
这正是为何森林管理员有时故意进行可控制的火烧，藉此减少可燃物，
in order to keep the more dangerous wildfires at bay.
避免更危险的森林大火。
They may be frightening and destructive forces of nature,
森林大火或许是骇人的自然破坏
but wildfires are also vital to the existence of healthy boreal forest ecosystems.
但它们对于维持北方针叶林的健康生态系统必不可少
By coming to terms with that, we can protect ourselves from their more damaging effects
接受这样的事实，我们可保护自己，免于它们进一步的伤害
while enabling the forests, like the legendary phoenix, to rise reborn from their own ashes.
同时，让森林如同传说中的凤凰从自身的灰烬中浴火重生。