PBS高端访谈:气候变化正在减少雄性海龟的数量

 　　GWEN IFILL: Now we turn to another angle of our continuing of climate change and its impact.

　　Tonight, our science team looks at the toll¹ it is taking on sea turtles and some of their tiniest offspring. We went to the coast of Southern Florida and came back with a major report that we are launching on our Web site tonight. Here's a part of it.

　　JEANETTE WYNEKEN, Florida Atlantic University: Turtles go back around 230 million years. Sea turtles go back around 110 million years.

　　And while I'm happy to report that we have had a really big nesting year this year and last year, the numbers are still depleted² from what they have been historically. So we're not looking at a species that is out of the woods yet.

　　When we think about the biology of the animal, the loggerhead has been around for around 60 million years. There have been a lot of climatic changes during that time, and very few of them have occurred at this rate.

　　It changes where the droughts occur. It changes where the heavy rainfall events occur. It changes where major tropical storms occur and the sizes of the tropical storms. The shift in climate is shifting turtles as well.

　　Now, one of the things that we discovered from those major rainfall amounts or major storm surge events, that we can see the changing in the temperature of the nest. So the reason why the temperature matters is because sea turtles have environmentally determined³ sex. They don't have an X or Y chromosome⁴. They have a sex that's defined during development by the incubation environment.

　　And In general, we have higher biased⁶ sex ratios, where female bias⁵ is common. If the sand absorbs more heat, we're going to push that female bias, which we know is really common down here, to an even more extreme situation.

　　So, a typical loggerhead down here in Southern Florida is producing about 105 eggs. If a female nests five times, five times 105, if my math is good today, should be 525 eggs. So she will have to nest over 10 nesting seasons, which is about a — in the case of a loggerhead, a 20- or 30-year period, just to replace herself and maybe one mate.

　　If you do a back-of-the-envelope calculation, we're looking at about one in 7,000 making it to adulthood⁷. Let's take that same turtle and her nesting over 20 years, so that's 10 nesting events. If five of those, everything gets wiped out by storms, and five of those are drought years where turtle production is low, and it's so hot that everything that comes out of the nest is a female, wow, as long as they can find a date, they have got a future.

　　But if there aren't enough males out there, then — then there is a problem. They have been through some climate changes, but we hope this climate-changing event is not one that they can't recover from, that they can't compensate⁸ for. And if it is so bad that they can't compensate, that's a pretty dire⁹ statement, not only for the turtles, but for us.

　　GWEN IFILL: I'm joined now by science producer Nsikan Akpan.

　　So, Nsikan, you're a science guy, so you know about melting glaciers¹⁰ and polar bears. Tell us why we care about loggerhead turtles.

　　NSIKAN AKPAN: So, we're calling the series the Wild Side of Sea Level Rise, because we're looking at the infinite little ways that sea level rise will impact wildlife along the coasts.

　　Now, if you look at adult sea turtles, they are not that small, right? They are not that tiny. We know a leatherback can weigh as much as a motorcycle.

　　GWEN IFILL: Huh.

　　NSIKAN AKPAN: But sea level rise is going to have a huge impact on their very small nestlings.

　　So, as Janet mentioned in the — or Jeanette mentioned in the video, sea level rise is washing out nests at a higher frequency than we have seen in the past. Storm surges are a part of that. And then we also have this issue with beach erosion, which is squeezing the amount of area that sea turtles have to nest.

　　GWEN IFILL: Now, I highly recommend people going and reading your report, which is very interesting.

　　But one of the things that struck me was, you found that — you reported that only one in 7,000 of these loggerheads, once they're born, actually make it to adulthood.

　　NSIKAN AKPAN: Right.

　　So, sea turtles, and especially their hatchlings, often serve as prey¹¹ for a lot of predators¹². So, while we were out there on the beach, producer Mike Fritz and I, we saw a fox running around the beach. And one of the researchers told us that a fox could eat an entire nest of sea turtle eggs, so it could eat 100 eggs in a single sitting.

　　Once the hatchlings make it off the beach and into water, they're often prey for sharks. And so then, when you compound the fact that so few survive natural predation with the fact that beach erosion — or beach erosion and also storm surges washing out more nests, you are going to have sea turtles sort of pushed to the brink¹³ in terms of their genetic¹⁴ diversity and also just their population numbers overall.

　　GWEN IFILL: Predators have always been thus, right?

　　But what's different now, it seems that we're talking about the effects of drought and, as you mentioned, erosion and warming and storm surges. Of all of those factors, what would you say is the most dead — having the most deadly impact?

　　NSIKAN AKPAN: Well, I think all of those are having pretty cataclysmic effects.

　　As Jeanette mentioned in the — with her research, they're seeing that drought is forcing the sex ratio bias, where they are going to have almost primarily females being reproduced. And if you have that occur for multiple generations, you can lose a lot of diversity of sea turtles, but also just their ability to reproduce overall.

　　GWEN IFILL: So, what is the solution — or are there solutions, first of all, and are they — there solutions we can pay for?

　　NSIKAN AKPAN: One solution is beach renourishment, which is when you ship sand from offshore¹⁵ and you just try to physically¹⁶ rebuild the beach.

　　For a couple of different reasons, that isn't always the great for sea turtles. Sea turtles have a harder time digging into a renourished beach. Their nests are often misshapen, which can prevent hatchlings from being able to escape. And you just end up with a big trap.

　　GWEN IFILL: And it's an expensive prospect¹⁷, also.

　　NSIKAN AKPAN: It's also very expensive.

　　So, since 1991, Florida has spent over $2 billion to renourish beaches. And if you think about it — if you think about this prospect long term, it isn't very sustainable, because sea levels are predicted to rise by at least five feet by 2100, which — so, beach renourishment isn't really a solution in that case, right?

　　GWEN IFILL: Right.

　　Well, Nsikan, you introduced me to something I knew nothing about and now I find terribly interesting. So, thank you very much.

　　NSIKAN AKPAN: Thank you, Gwen.

 

1 toll   

n.过路(桥)费；损失，伤亡人数；v.敲(钟)

参考例句：

• The hailstone took a heavy toll of the crops in our village last night.昨晚那场冰雹损坏了我们村的庄稼。
• The war took a heavy toll of human life.这次战争夺去了许多人的生命。

2 depleted   

adj. 枯竭的, 废弃的 动词deplete的过去式和过去分词

参考例句：

• Food supplies were severely depleted. 食物供应已严重不足。
• Both teams were severely depleted by injuries. 两个队都因队员受伤而实力大减。

3 determined   

adj.坚定的；有决心的

参考例句：

• I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
• He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。

4 chromosome   

n.染色体

参考例句：

• Chromosome material with exhibits of such behaviour is called heterochromatin.表现这种现象的染色体物质叫做异染色质。
• A segment of the chromosome may become lost,resulting in a deletion.染色体的一个片段可能会丢失，结果产生染色体的缺失。

5 bias   

n.偏见，偏心，偏袒；vt.使有偏见

参考例句：

• They are accusing the teacher of political bias in his marking.他们在指控那名教师打分数有政治偏见。
• He had a bias toward the plan.他对这项计划有偏见。

6 biased   

a.有偏见的

参考例句：

• a school biased towards music and art 一所偏重音乐和艺术的学校
• The Methods: They employed were heavily biased in the gentry's favour. 他们采用的方法严重偏袒中上阶级。

7 adulthood   

n.成年，成人期

参考例句：

• Some infantile actions survive into adulthood.某些婴儿期的行为一直保持到成年期。
• Few people nowadays are able to maintain friendships into adulthood.如今很少有人能将友谊维持到成年。

8 compensate   

vt.补偿，赔偿；酬报 vi.弥补；补偿；抵消

参考例句：

• She used her good looks to compensate her lack of intelligence. 她利用她漂亮的外表来弥补智力的不足。
• Nothing can compensate for the loss of one's health. 一个人失去了键康是不可弥补的。

9 dire   

adj.可怕的，悲惨的，阴惨的，极端的

参考例句：

• There were dire warnings about the dangers of watching too much TV.曾经有人就看电视太多的危害性提出严重警告。
• We were indeed in dire straits.But we pulled through.那时我们的困难真是大极了，但是我们渡过了困难。

10 glaciers   

冰河，冰川( glacier的名词复数 )

参考例句：

• Glaciers gouged out valleys from the hills. 冰川把丘陵地带冲出一条条山谷。
• It has ice and snow glaciers, rainforests and beautiful mountains. 既有冰川，又有雨林和秀丽的山峰。 来自英语晨读30分（高一）

11 prey   

n.被掠食者，牺牲者，掠食；v.捕食，掠夺，折磨

参考例句：

• Stronger animals prey on weaker ones.弱肉强食。
• The lion was hunting for its prey.狮子在寻找猎物。

12 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

13 brink   

n.(悬崖、河流等的)边缘，边沿

参考例句：

• The tree grew on the brink of the cliff.那棵树生长在峭壁的边缘。
• The two countries were poised on the brink of war.这两个国家处于交战的边缘。

14 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。

15 offshore   

adj.海面的，吹向海面的；adv.向海面

参考例句：

• A big program of oil exploration has begun offshore.一个大规模的石油勘探计划正在近海展开。
• A gentle current carried them slowly offshore.和缓的潮流慢慢地把他们带离了海岸。

16 physically   

adj.物质上，体格上，身体上，按自然规律

参考例句：

• He was out of sorts physically,as well as disordered mentally.他浑身不舒服，心绪也很乱。
• Every time I think about it I feel physically sick.一想起那件事我就感到极恶心。

17 prospect   

n.前景，前途；景色，视野

参考例句：

• This state of things holds out a cheerful prospect.事态呈现出可喜的前景。
• The prospect became more evident.前景变得更加明朗了。