VOA标准英语2015--河马创造了河流生命力

Hippos Called River Life Force 河马创造了河流生命力

A new study says the hippopotamus¹ is very important to the health of Africa’s rivers and lakes. That’s because hippos produce a key ingredient for aquatic² life -- and a lot of it. But researchers warn that hippo populations are on the decline and that could damage ecosystems⁴.

The mighty⁵ hippopotamus is the third largest land mammal following the elephant and rhinoceros⁶. Its name is derived⁷ from the ancient Greek for river horse. Hippos spend up to 16 hours a day in the water and venture on to land at night to feed. They eat tropical grasses, more than 200 kilograms per meal. And what goes in must come out. And there is the magic ingredient for Africa’s aquatic ecosystems – dung.

Douglas McCauley and his colleagues decided⁸ to study it.

“Well, we started looking at hippopotamus and realized that a big part of the story was their poop – was this vast amount of nutrients¹⁰ and energy that are moved across systems via their eating and their defecation,” he said.

McCauley is an assistant professor of ecology, evolution and marine¹¹ biology at the University of California Santa Barbara. He said hippos cross the boundaries of ecosystems.

“Transiting between two different domains¹² – between land, the terrestrial world, and then the aquatic world – means that there are also these important nutrient⁹ vectors. Because their eating lots and lots of stuff on land and then taking that all back to the place where they rest in the water -- in lakes and rivers -- and then basically dunging that all out. And it turns out when you start crunching¹³ the numbers to be a huge amount of material and energy and nutrients of this sort of natural fertilizer that is moved across these boundaries,” he said.

So, each hippo contributes, if you will, over 60,000 kilograms of dung to African lakes and rivers every year.

“It’s a big animal,” he said, “We’re talking about an animal that’s about 4,000 to 8,000 pounds. So, it’s got a big appetite. When you look across the entire continent and our estimate of how many hippos we now have in sub-Saharan Africa that comes out to millions of kilograms.”

So, by now you understand it’s a tremendous amount of dung. But did you know that hippo dung looks like straw?

“That’s right. So, they are mostly feeding on grass, sort of a straw-like grass. In fact, a lot of African grasses are used as straw and forage¹⁴ for cattle in places like America. So, they have these wonderfully well-developed lips that they use like a lawnmower to go across these short grass lawns that they actually manicure. And they keep them short because it seems to keep this resource accessible just to them,” said McCauley.

McCauley said it’s even used as a communication device.

“They actually use dung as a kind of signal amongst themselves. So, a male animal will dung at a sub-dominant male. They actually fling it back and forth¹⁵ with their paddle-like tail.”

But the really important thing about hippo dung is its place in the food chain.

“Well, there’s a lot of good stuff in dung. There’s a lot of nitrogen, carbon, even a bit of phosphorus. And some of these nutrients can be limiting in river systems. These are sort of the building blocks of life in some cases. So it really is injecting more of this food into these rivers. And a lot of the animals it seems in the rivers are quite happy to receive it. Some of them eat it up directly and some consumers, like fish, will eat insects that started their lives feeding on dung,” he said.

McCauley actually described it as a life force in Africa’s rivers and lakes. But he said if the water flow is too low, the dung could overwhelm the ecosystem³ and be a pollutant¹⁶. Too much water and its value is diluted¹⁷.

But as researchers learn more about the importance of hippos, there are fewer of them.

“Hippos are declining across sub-Saharan Africa. In the past decade or so, we’ve seen about a 10 to 20 percent decline in their numbers. And beyond how many there are they’re in a lot fewer places. There are entire countries that have completely lost hippopotamus -- Egypt, for example. Hippos used to be an iconic god. It was the god of birth in Egypt. You see the hippo god. It’s a goddess turning up on amulets¹⁸ and wands and swords,” he said.

McCauley said humans are responsible for most of the decline in the hippo population through hunting and habitat loss as human populations spread.

“They have to have water. Well, guess what? Everybody else wants water. And it’s really unfortunate if you’ve tied your fate to water because when you compete with humans for water you often lose. So, people want water from rivers and lakes for building out cities – for helping¹⁹ to cool turbines– or damming rivers,” he said.

It’s estimated hippos kill about 3,000 people a year. The animals may attack, for example, if people get too near a mother and calf²⁰.

McCauley said careful thought must be given to the management of water, both for humans and wildlife. He says if managed intelligently, there should be plenty of water to go around, adding that the fates of humans, wildlife and ecosystems are closely tied together.

The study appeared in the journal Ecosphere.

1 hippopotamus   

n.河马

参考例句：

• The children enjoyed watching the hippopotamus wallowing in the mud.孩子们真喜观看河马在泥中打滚。
• A hippopotamus surfs the waves off the coast of Gabon.一头河马在加蓬的海岸附近冲浪。

2 aquatic   

adj.水生的，水栖的

参考例句：

• Aquatic sports include swimming and rowing.水上运动包括游泳和划船。
• We visited an aquatic city in Italy.我们在意大利访问过一个水上城市。

3 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

4 ecosystems   

n.生态系统( ecosystem的名词复数 )

参考例句：

• There are highly sensitive and delicately balanced ecosystems in the forest. 森林里有高度敏感、灵敏平衡的各种生态系统。 来自《简明英汉词典》
• Madagascar's ecosystems range from rainforest to semi-desert. 马达加斯加生态系统类型多样，从雨林到半荒漠等不一而足。 来自辞典例句

5 mighty   

adj.强有力的；巨大的

参考例句：

• A mighty force was about to break loose.一股巨大的力量即将迸发而出。
• The mighty iceberg came into view.巨大的冰山出现在眼前。

6 rhinoceros   

n.犀牛

参考例句：

• The rhinoceros has one horn on its nose.犀牛鼻子上有一个角。
• The body of the rhinoceros likes a cattle and the head likes a triangle.犀牛的形体像牛，头呈三角形。

7 derived   

vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取

参考例句：

• Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
• He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》

8 decided   

adj.决定了的，坚决的；明显的，明确的

参考例句：

• This gave them a decided advantage over their opponents.这使他们比对手具有明显的优势。
• There is a decided difference between British and Chinese way of greeting.英国人和中国人打招呼的方式有很明显的区别。

9 nutrient   

adj.营养的，滋养的；n.营养物，营养品

参考例句：

• Magnesium is the nutrient element in plant growth.镁是植物生长的营养要素。
• The roots transmit moisture and nutrient to the trunk and branches.根将水分和养料输送到干和枝。

10 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

11 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

12 domains   

n.范围( domain的名词复数 )；领域；版图；地产

参考例句：

• The theory of thermodynamics links the macroscopic and submicroscopic domains. 热力学把宏观世界同亚微观世界联系起来。 来自辞典例句
• All three flow domains are indicated by shading. 所有三个流动区域都是用阴影部分表示的。 来自辞典例句

13 crunching   

v.嘎吱嘎吱地咬嚼( crunch的现在分词 )；嘎吱作响；（快速大量地）处理信息；数字捣弄

参考例句：

• The horses were crunching their straw at their manger. 这些马在嘎吱嘎吱地吃槽里的草。 来自《简明英汉词典》
• The dog was crunching a bone. 狗正嘎吱嘎吱地嚼骨头。 来自《简明英汉词典》

14 forage   

n.(牛马的)饲料，粮草；v.搜寻，翻寻

参考例句：

• They were forced to forage for clothing and fuel.他们不得不去寻找衣服和燃料。
• Now the nutritive value of the forage is reduced.此时牧草的营养价值也下降了。

15 forth   

adv.向前；向外，往外

参考例句：

• The wind moved the trees gently back and forth.风吹得树轻轻地来回摇晃。
• He gave forth a series of works in rapid succession.他很快连续发表了一系列的作品。

16 pollutant   

n.污染物质，散布污染物质者

参考例句：

• Coal itself is a heavy pollutant.煤本身就是一种严重的污染物。
• Carbon dioxide may not be a typical air pollutant.二氧化碳可能不是一种典型的污染物。

17 diluted   

无力的，冲淡的

参考例句：

• The paint can be diluted with water to make a lighter shade. 这颜料可用水稀释以使色度淡一些。
• This pesticide is diluted with water and applied directly to the fields. 这种杀虫剂用水稀释后直接施用在田里。

18 amulets   

n.护身符( amulet的名词复数 )

参考例句：

• Amulets,\"guards,\" as they are popularly called, intended to ward off evil spirits. 护身符――或者象他们普遍的叫法：“警卫”用来抵御妖魔鬼怪。 来自辞典例句
• However, all oval amulets in a single game are the same. 当然，所有的魔法用品也有类似的情形。 来自互联网

19 helping   

n.食物的一份&adj.帮助人的，辅助的

参考例句：

• The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
• By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。

20 calf   

n.小牛，犊，幼仔，小牛皮

参考例句：

• The cow slinked its calf.那头母牛早产了一头小牛犊。
• The calf blared for its mother.牛犊哞哞地高声叫喊找妈妈。