最近在澳大利亞我參觀了一片桉樹林，那里剛剛發(fā)生了一場可怕的火災(zāi)。我之前曾經(jīng)天真地認為很多樹肯定都被燒死了，不過沒有。樹皮都被燒黑了，但是看起來這些桉樹長得卻相當(dāng)好，很多書都長處了很多新葉子。這促使我想到了那場大火以及它作為自然力量所發(fā)揮的作用。
石炭告訴我們，野火在陸地上出現(xiàn)植物后就一直是地球生命的一部分�；鹪诓葸@類植物存在前很久就存在;而且吞噬了第1批花朵。因為不想把它變得很神秘，所以說火在很多方面是一種動物，盡管是種飄渺不定的動物。像任何一種動物一樣，它消耗氧氣。它像綿羊一樣吞食植物。它有時僅僅咬掉幾片葉子，有時卻燒死長成的大樹。有時它比成群的蝗蟲更加致命，更具破壞力。
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火不斷變換形態(tài)的性質(zhì)使它很難研究。有些火焰像地獄般炙熱;有些則相當(dāng)涼爽。有些火焰呆在地面上;另一些則爬上了樹。此外，世界上有些地方的火災(zāi)比其他地方要頻繁地多。地球的衛(wèi)星成像顯示如歐洲北部這樣的地方很少出現(xiàn)野火，而非洲中部的一些地方和澳大利亞則常有野火。
火焰一旦燃起，其行動就會受到很多因素的影響。很明顯，天氣對此有著極大的影響： 風(fēng)能煽起火焰，雨則能撲滅火焰。陸地的走勢也有影響：火焰順山勢而上比沿山坡向下要快得多。但另一個關(guān)鍵因素是：火焰將吞噬哪類植物。
有一項常識：那些經(jīng)常接受火焰考驗的植物會擁有有助它們應(yīng)對火災(zāi)的特征——如厚厚的樹皮或只有經(jīng)過烈火和濃煙的磨練才會生長的種子。
When in Australia recently, I visited a eucalyptus forest that was once the scene of an appalling wildfire. Perhaps naively, I had expected to find that many trees had been killed .They hadn’t. They had blackened bark, but were otherwise looking rather well, many of them wreathed in new young leaves. This prompted me to consider fire and the role it plays as a force of nature.
Fossil charcoals tell us that wildfires have been part of life on the earth for as long as there have been plants on land. Fire was here long before such plants as grasses; it predated the first flowers. And without wanting to get mystical about it, fire is ,in many respects , a kind of animal, albeit an ethereal one .Like any animal, it consumes oxygen .Like a sheep, it eats plants. Sometimes, it merely nibbles a few leaves; sometimes it kills grown trees. Sometimes it is more deadly and destructive than a swarm of locusts.
The shape-shifting nature of fire makes it hard to study. Some fires are infernally hot; others, relatively cool. Some stay at ground level; others climb trees. Moreover, fire is much more likely to appear in some parts of the world than in others. Satellite images of the earth show that wildfires are rare in, say, Northern Europe, and common in parts of Central Africa and Australia.
Once a fire gets started, many factors contribute to how it will behave. The weather obviously has a huge effect: winds can fan flames, rains can quench them. The lie of the land matters, too: fire runs uphill more readily than it goes down. But another crucial factor is what type of plants the fire has to eat.
It’s common knowledge that plants regularly exposed to fire tend to have features that help them cope with it, such as thick bark, or seeds that only grow after being exposed to intense heat or smoke.
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