科学美国人60秒 SSS 河马可能危及哥伦比亚的生态环境

This is Scientific American's 60-second Science. I'm Jason Goldman.

Around 115 miles east of Medellín, in Colombia, sits the enormous hacienda built by the drug lord Pablo Escobar—who had his own personal zoo, which included hippos. When Escobar's empire fell, most of the exotic animals were safely relocated—except for the hippos, who eventually escaped.

"So he brought four from a zoo in the U.S. to Colombia, and they lived at his ranch¹. And they've grown slowly but steadily²."

Jonathan Shurin, ecologist from the University of California in San Diego.

The original population of four in 1981 is estimated to be at least 80 now. Hippos have a tremendous influence on their native ecosystems⁴ in Africa, so Shurin wanted to see how they might be affecting their new ecosystem³ in Colombia.

"It shouldn't be a surprise to anybody that hippos poop in the water in South America, just as they do in Africa."

Hippos on both continents wallow in ponds and lakes, where their droppings release a tremendous amount of nutrients⁵ into the water.

"That imported material stimulates⁶ photosynthesis⁷ of algae⁸ and aquatic⁹ plants and also microbial bacterial¹⁰ production—bacteria that are living off of the organic matter that's imported."

And that's where the hippos can cause ecological¹¹ trouble. If there is too much photosynthesis occurring, then the water becomes full of oxygen during the daytime. But at night, when the sun goes down, and the plants and algae stop releasing oxygen into the water, a phenomenon called eutrophication occurs. All the creatures that consume oxygen keep consuming it, and the overall amount of oxygen dissolved in the water becomes critically low.

"The oxygen dropping low enough—you can have all the fish sort of croaking¹² and going belly-up."

The researchers also say the situation provides a unique glimpse into the way that massive mammals like mammoths and mastodons, long extinct in the New World, may have influenced their habitats prior to their extinction¹³.

But they also note that unless we can somehow curtail¹⁴ their population growth, the hippo population could explode in the next couple of decades—at which point, they will disrupt larger and wilder river systems. The study is in the journal Ecology.

Lethal¹⁵ control isn't a popular management strategy among people who love hippos or see them as a valuable tourism attraction. But the question is when, not if, the hippos become detrimental¹⁶ to Colombian ecology—which means that folks should be thinking about the best way to solve the problem now, when there are fewer than a hundred hippos to manage and not thousands.

Thanks for listening for Scientific American's 60-second Science. I'm Jason Goldman.

这里是科学美国人——60秒科学。我是杰森·古德曼。

哥伦比亚麦德林以东115英里处，坐落着毒枭帕布罗·埃斯科巴建造的巨型庄园，拥有私人动物园，园中的动物包括河马。埃斯科巴帝国衰落后，大多数海外动物都被安全迁移，但最终逃跑的河马除外。

“他从美国动物园买了四只河马运到哥伦比亚，养在他的庄园里。这些河马缓慢但稳定地生长。”

加州大学圣地亚哥分校的生态学家乔纳森·舒林说到。

据估计，1981年原种群的4只河马如今至少繁殖为80只。河马对非洲原生态系统有着巨大的影响，因此舒林想了解它们可能对哥伦比亚新生态系统产生的影响。

“和在非洲一样，河马在南美洲也在水中排便，这对任何人来说都不应该感到惊讶。”

两大洲的河马都在池塘和湖中打滚，它们的粪便会向水中释放大量养分。

“进口物质会刺激藻类和水生植物的光合作用，也会刺激微生物细菌的产生，这些细菌靠进口有机物为生。”

这就是河马可能导致生态问题的地方。如果产生太多光合作用，那白天水中就会充满氧气。但到了晚上，太阳下山，植物和藻类停止向水中释放氧气时，就会发生一种名为“富营养化”的现象。消耗氧气的所有生物会继续消耗氧气，而水中溶氧总量会急剧减少。

“水中氧气下降到足够低时，可能会让所有鱼都会因缺氧而死亡。”

研究人员还表示，这种情况提供了独特的视角，让我们得以了解猛犸象和乳齿象等早已在美洲大陆灭绝的大型哺乳动物，在灭绝之前影响栖息地的方式。

但他们也注意到，除非我们能以某种方式加以控制，否则河马数量可能在未来几十年内呈现爆炸式增长，届时，它们会破坏更大、更野生的河系。这项研究发表在《生态学》期刊上。

喜欢河马或将其视为珍贵旅游资源的人，并不欢迎致命控制这种管理策略。但问题是，河马何时——而非是否——会对哥伦比亚的生态环境造成危害，也就是说，人们现在应该考虑解决问题的最佳方法，因为现在河马数量少于一百只，而不是几千只。

谢谢大家收听科学美国人——60秒科学。我是杰森·古德曼。

1 ranch   

n.大牧场，大农场

参考例句：

• He went to work on a ranch.他去一个大农场干活。
• The ranch is in the middle of a large plateau.该牧场位于一个辽阔高原的中部。

2 steadily   

adv.稳定地；不变地；持续地

参考例句：

• The scope of man's use of natural resources will steadily grow.人类利用自然资源的广度将日益扩大。
• Our educational reform was steadily led onto the correct path.我们的教学改革慢慢上轨道了。

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 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》

6 stimulates   

v.刺激( stimulate的第三人称单数 )；激励；使兴奋；起兴奋作用，起刺激作用，起促进作用

参考例句：

• Exercise stimulates the body. 运动促进身体健康。 来自《简明英汉词典》
• Alcohol stimulates the action of the heart. 酒刺激心脏的活动。 来自《现代英汉综合大词典》

7 photosynthesis   

n.光合作用

参考例句：

• In apple trees photosynthesis occurs almost exclusively in the leaves.苹果树的光合作用几乎只发生在叶内。
• Chloroplasts are the structures in which photosynthesis happens.叶绿体就是光合作用发生的地方。

8 algae   

n.水藻，海藻

参考例句：

• Most algae live in water.多数藻类生长在水中。
• Algae grow and spread quickly in the lake.湖中水藻滋蔓。

9 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。

10 bacterial   

a.细菌的

参考例句：

• Bacterial reproduction is accelerated in weightless space. 在失重的空间，细菌繁殖加快了。
• Brain lesions can be caused by bacterial infections. 大脑损伤可能由细菌感染引起。

11 ecological   

adj.生态的，生态学的

参考例句：

• The region has been declared an ecological disaster zone.这个地区已经宣布为生态灾难区。
• Each animal has its ecological niche.每种动物都有自己的生态位.

12 croaking   

v.呱呱地叫( croak的现在分词 )；用粗的声音说

参考例句：

• the croaking of frogs 蛙鸣
• I could hear croaking of the frogs. 我能听到青蛙呱呱的叫声。 来自《简明英汉词典》

13 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

14 curtail   

vt.截短，缩短；削减

参考例句：

• The government hopes to curtail public spending.政府希望缩减公共事业开支。
• The minister had to curtail his visit.部长不得不缩短访问日期。

15 lethal   

adj.致死的；毁灭性的

参考例句：

• A hammer can be a lethal weapon.铁锤可以是致命的武器。
• She took a lethal amount of poison and died.她服了致命剂量的毒药死了。

16 detrimental   

adj.损害的，造成伤害的

参考例句：

• We know that heat treatment is detrimental to milk.我们知道加热对牛奶是不利的。
• He wouldn't accept that smoking was detrimental to health.他不相信吸烟有害健康。