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An animal species becomes extinct when it fails to produce enough young is each generation to keep pace with the death-rate. We can tell from fossil evidence in rocks that many living species have become extinct over the millions of years since life began. It is a natural process and extinction is the fate of many animal that has specialized too far to change when its environment changes, or has to compete with a better-adapted and more powerful animal. Because of remarkable technical developments during the past few centuries, man has destroyed or nearly destroyed some species by killing them at such a rate that they couldn't produce enough offspring, or by completely changing their natural environment at surprising speed.
A number of examples can be given of the way in which natural environments are being rapidly changed - Amazonia, for instance. There is every likelihood that many species of animals will be made extinct because of these and similar clearances of natural vegetation. Large numbers of animals have been hunted and killed for food. The North American buffalo is a case of the near-extinction of a species through hunting. Often the numbers are so great the hunters may not realize the danger. But even when the danger is widely publicized, the financial rewards for the hunters may be so great that they choose to ignore the threat to the species. Attitudes like this have led to hunters killing animals for furs, for ivory or merely for ornaments. A slight variation on this is when tourists hunt animals for trophies. Magnificent creatures such as lions and tigers have been hunted out of existence in some parts of the world. It is important to realise, though, that animals are sometimes killed out of fear. Big cats are killed in this way. And animals are sometimes killed out of a wish to reduce numbers to help the species to survive. The killing of the Canadian seals is claimed to be for this purpose, and the use of their skins for furs is only a by-product.
Many people are concerned about animals and wildlife conservation. One way to preserve species under threat of extinction - whatever the cause - is to remove them to zoos and parks and breed them there. There is always the chance that enough offspring will be born to return them one day to their natural environment - provided it still exists, and that hunters don't kill them again! Another method is to protect the animals in their natural environment by creating wildlife reserves and parks and using game wardens to look after them. But the parks are large, the wardens few and the determination of hunters very great. Early in 1980 wardens and hunters clashed in East Africa. The hunters were armed with modern weapons and several people were killed.
There is great pleasure in watching wildlife in natural or near-natural environments, and tourism can add to the income of countries. The animals are still resources - but in a very different form.
种种动物都濒临灭绝的危险境地,有谁关心?
不论何种动物,只要每一代不能繁殖出足够的后代,不能与这种动物的死亡数字相平衡,那么这种动物就会逐渐灭绝。我们从岩石中的化石遗留下的证据中可以辨别出来,自从地球上有生命时开始,在若干个百万年中,有很多动植物的物种已经逐渐地灭绝了。任何一种生性过于特殊化以致于不能随着环境的变化而改变自己的特性的动物,或者是任何一种必须与一种能更好地适应环境而又更加强大的动物相竞争的动物,它们的命运都将是灭绝,这是个很自然的演化过程。由于最近几百年来各项科学技术的迅猛发展,以惊人的速度大量杀死了某些种动物,或以惊人的速度彻底改变了这些动物的生存的自然环境,致使这些动物不能生育繁衍出足够的后代,人类已经消灭了或已经接近于消灭了某些种动物。
可以举出很多很多的例子说明自然生态环境已经被迅速地改变了,亚马逊河流域就是最好的例证。因为在这些地区以及和这些地区相类似的地区,自然界的植物已经被砍伐净尽,许多种动物将完全有可能灭绝。一大批一大批的动物被当作食品而遭猎杀。北美洲的野牛就是因为捕猎而接近于灭绝的物种之一。这些动物的数量非常庞大,以致于猎手们意识不到这些动物会有灭绝的危险。但即使是把这种动物行将灭绝的危险已经广泛地公诸于众,偷猎对猎人们财务上的回报是非常巨大的,以致猎人们选定了对这些物种行将灭绝的危险采取不理不睬的态度。这类态度已经导致了猎人为了获得毛皮、获得象牙或者仅仅是为了用作装饰品就去猎杀动物。与此稍有不同的是,那些旅游观光客错杀动物是为了留作战胜猎物的纪念品。像狮子、老虎之类雄伟的动物在世界有些地区已经灭绝了。然而要注意到,有时人们杀死了动物是由于人们害怕,这一点是很重要的。大猫科的动物就是这样被杀死的。有时杀死一些动物是希望减少一些数目,以便有助于这种动物能生存下去。据说杀死了一批加拿大的海豹就是为了这个目的,而利用海豹皮只是一种副产物而已。
许多人都关心动物及野生动植物的保护工作。不管是什么原因造成了灭绝,一种保存遭受灭绝威胁的物种的办法就是把这些物种搬进动植物园里面去,并让这些动植物在那里生息繁衍下来。假如这种动物能存活下来,假如猎手们不再杀死它们,那么等将来它们繁衍出足够的后代之后,总会有这样的机会,总有一天会让它们的大自然的环境中去!另一种在自然环境中保护动物的办法,就是创建野生动植物保护区和野生动植物园并设置禁止渔猎野生动物监督官来看护这些动物。但是野生动植物园范围很广大,禁止渔猎野生动物监督官人手又很少,偷猎野生动物的猎人们的偷猎决心都很大。1980年初监督官与猎手们发生了冲突。猎手们都装备有现代化的武器,结果有数人在冲突中死亡。
在大自然当中或在接近于大自然的环境当中,欣赏野生动植物,真是一大赏心乐事,况且这种旅游观光业也能为国家或地方增加收入。各种动物都依然是我们的资源--但却是一种不同形式的资源。 |
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