Official 39 Passage 3


Forest Fire Suppression


According to paragraph 5, people in the United States would probably not support the described forest-management and restoration techniques because they

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  • A
    think that the use of small, controlled fires may be too dangerous
  • B
    do not want to spend money on the expensive process of managing forest understory
  • C
    distrust the Forest Service due to the harmful fire-suppression techniques of the past
  • D
    do not want politicians involved in forest management
正确答案: B

我的笔记 编辑笔记

  • 原文
  • 译文
  • Forest fires have recently increased in intensity and extent in some forest types throughout the western United States. This recent increase in fires has resulted partly from climate change (the recent trend toward hot, dry summers) and partly from human activities, for complicated reasons that foresters came increasingly to understand about 30 years ago but whose relative importance is still debated. One factor is the direct effect of logging, which often turns a forest into something approximating a huge pile of kindling (wood for burning): the ground in a logged forest may remain covered with branches and treetops, left behind when the valuable trunks are carted away; a dense growth of new vegetation springs up, further increasing the forest's fuel loads; and the trees logged and removed are of course the biggest and most fire-resistant individuals, leaving behind smaller and more flammable trees.

    Another factor is that the United States Forest Service in the first decade of the 1900s adopted the policy of fire suppression (attempting to put out forest fires) for the obvious reason that it did not want valuable timber to go up in smoke, or people's homes and lives to be threatened. The Forest Service's announced goal became "Put out every forest fire by 10:00 A.M. on the morning after the day when it is first reported." Firefighters became much more successful at achieving that goal after 1945, thanks to improved firefighting technology. For a few decades the amount of land burnt annually decreased by 80 percent. That happy situation began to change in the 1980s, due to the increasing frequency of large forest fires that were essentially impossible to extinguish unless rain and low winds combined to help.People began to realize that the United States federal government's fire-suppression policy was contributing to those big fires and that natural fires caused by lightning had previously played an important role in maintaining forest structure.

    The natural role of fire varies with altitude, tree species, and forest type. To take Montana's low-altitude ponderosa pine forest as an example, historical records, plus counts of annual tree rings and datable fire scars on tree stumps, demonstrated that a ponderosa pine forest experiences a lightning-lit fire about once a decade under natural conditions (i.e., before fire suppression began around 1910 and became effective after 1945). The mature ponderosa trees have bark two inches thick and are relatively resistant to fire, which instead burns out the understory-the lower layer-of fire-sensitive Douglas fir seedlings that have grown up since the previous fire. But after only a decade's growth until the next fire, those young seedling plants are still too low for fire to spread from them into the crowns of the ponderosa pine trees. Hence the fire remains confined to the ground and understory. As a result, many natural ponderosa pine forests have a parklike appearance, with low fuel loads, big trees spaced apart, and a relatively clear understory.

    However, loggers concentrated on removing those big, old, valuable, fire-resistant ponderosa pines, while fire suppression for decades let the understory fill up with Douglas fir saplings that would in turn become valuable when full-grown. Tree densities increased from 30 to 200 trees per acre, the forest's fuel load increased by a factor of 6, and the government repeatedly failed to appropriate money to thin out the saplings. When a fire finally does start in a sapling-choked forest, whether due to lightning or human carelessness or (regrettably often) intentional arson, the dense, tall saplings (young trees) may become a ladder that allows the fire to jump into the crowns of the trees. The outcome is sometimes an unstoppable inferno.

    Foresters now identify the biggest problem in managing Western forests as what to do with those increased fuel loads that built up during the previous half century of effective fire suppression. In the wetter eastern United States, dead trees rot away more quickly than in the drier West, where more dead trees persist like giant matchsticks. In an ideal world, the Forest Service would manage and restore the forests, thin them out, and remove the dense understory by cutting or by controlled small fires. But no politician or voter wants to spend what it would cost to do that.

  • 近期,发生在美国西部地区的一些森林中的森林火灾,无论是强度还是范围,都有所增加。 近期火灾的上升趋势一部分是由于气候变化(夏天变得更热更干燥),另一部分是由于人类活动。由于一些比较复杂的原因,护林人30年前就愈发认识到这一问题了,但是人类活动的重要性现在却仍存在争议。 一个因素是伐木作业的直接影响,伐木将森林变成一大堆引火物(等待被点燃的柴火):被砍伐了的森林的地面上仍会被树枝和树梢覆盖,更有价值的树干则被运走了;新的植被密集生长出来,进一步增加了森林里的燃料总量;被砍伐和运走的树木肯定是最大的也是最耐火的,剩下的都是小树和更加易燃的树木。

    另一个因素是美国林业局在二十世纪头十年采取的灭火政策,很显然他们不想让有价值的木材付之一炬,也不想让人们的家和生命安全受到威胁。 林业局声称的目标是“在接到火灾报告的第二天早上十点之前扑灭任何一个森林大火”。1945年之后,由于灭火技术的发展,消防员在达成这一目标上做的更加成功了。 数十年间,每年发生火灾的土地数量降低了80%。这一乐观的形势在二十世纪八十年代发生了改变,因为不断发生的森林大火,除非在雨水和低风的联合作用下,否则几乎不可能被扑灭。人们逐渐意识到,是联邦政府的灭火政策导致了这些大火的发生,因为之前,由闪电引导的自然火灾在维持森林构成方面起到了重要的作用。

    火灾的自然角色随着海拔高度、树木的种类和森林类型而异。 以蒙大拿州的低海拔的美国黄松林作为例子。历史记录、每年的年轮以及树桩上可以确定年代的火灾留下的疤痕都表明,在自然状态下,黄松林差不多每十年就要遭受一次由雷电引起的大火(也就是说,在灭火政策于1910年开始执行并于1945年后取得成效之前)。 成熟的黄松树树皮有两英寸厚,相对而言比较不易燃,着火的往往是上次火灾之后生长出来的道格拉斯冷杉幼苗,它们是森林的下层植被。 但是仅在这十年间长出来的幼苗仍然太矮,而不足以让火势蔓延至黄松树的树冠上去。 因此大火仅在地面和下层植被间燃烧。 因此许多自然生长的黄松林有点像公园,燃料量很少,树与树之间的间距大,下层植物比较少。

    但是,伐木工人正考虑砍除这些又大又老,很有价值又耐火的黄松树,因为多年来的灭火政策使得下层生长的道格拉斯冷杉幼树一旦生长成熟也可以变得非常有价值。 每英亩的树木数量从30株上升至200株,森林里的燃料总量增长了6倍,而政府又迟迟不能拿出拨款来减少幼苗的数量。 当长满幼苗的森林一旦开始着火,不管是由于雷电还是由于人类的疏忽,或者是非常令人遗憾的蓄意纵火,那些长得很高的幼苗可能变成了梯子,将火苗引至大树的树冠上。 结果就会造成无法遏制的地狱之火。

    护林人现在意识到,管理西部森林时面临的最大的问题在于如何处理这些不断增加的燃料总量,这些燃料是在过去的半个世纪间由于有效的灭火政策而积聚起来的。 在更加潮湿的美国东部,槁木比在更加干燥的西部腐烂的更快,在西部,更多的槁木像巨大的火柴棒一样存留在地面上。 在理想的情况下,林业局应该对森林进行管理和修复,增加树木间距,通过砍伐或者可控的小范围燃烧去除稠密的下层植被。 但是没有政客或者选民愿意花费这笔钱。
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    题干分析:关键词:the described forest-management and restoration techniques


    选项分析:根据题干关键词,定位最后两句In an ideal world, the Forest Service would manage and restore the forests, thin them out, and remove the dense understory by cutting or by controlled small fires. But no politician or voter wants to spend what it would cost to do that.”最后一句说明了原因,政客和选民不愿意花钱,因此选项B符合句意。