When will the next mass extinction occur? - Borths, D'Emic, and Pritchard

翻译人员: Lyn Beaumont 校对人员: Gabriella Hu

About 66 million years ago,

大约在六千六百万年以前，

something terrible happened to life on our planet.

我们的星球上的生命遭遇了一次恐怖的劫难。

Ecosystems were hit with a double blow

我们的生态系统遭受了双重打击

as massive volcanic eruptions filled the atmosphere with carbon dioxide

空气中弥漫着大规模的火山喷发带来的二氧化碳

and an asteroid roughly the size of Manhattan struck the Earth.

同时一个体积相当于曼哈顿的小行星撞击了地球。

The dust from the impact reduced or stopped photosynthesis from many plants,

大气中的尘埃严重得影响了许多植物的光合作用，

starving herbivores and the carnivores that preyed on them.

饥饿肆虐着食草动物和捕食它们的食肉动物。

Within a short time span,

在很短的时间内，

three-quarters of the world's species disappeared forever,

世界上四分之三的物种灭绝了，

and the giant dinosaurs,

许多巨型恐龙、

flying pterosaurs,

飞翼龙、

shelled squids,

甲壳类软体动物、

and marine reptiles that had flourished for ages

和那些世代繁衍的海洋爬行动物

faded into prehistory.

都从我们的史前史中渐渐消失了。

It may seem like the dinosaurs were especially unlucky,

恐龙看上去似乎非常不幸，

but extinctions of various severities have occurred throughout the Earth's history,

但这却是地球史上适者生存的法则，

and are still happening all around us today.

并且一直延续至今。

Environments change,

环境一直在变化，

pushing some species out of their comfort zones

挑战到一些物种的生存极限

while creating new opportunities for others.

同时也为其它一些物种创造新的机遇。

Invasive species arrive in new habitats, outcompeting the natives.

入侵物种在新的栖息地中战胜原生物种。

And in some cases, entire species are wiped out

有时是整个物种被歼灭，

as a result of activity by better adapted organisms.

这就是适者生存的法则。

Sometimes, however, massive changes in the environment

有时急剧的环境改变

occur too quickly for most living creatures to adapt,

让大部分生物来不及自身调整，

causing thousands of species to die off in a geological instant.

导致成千上万的物种在地质突变中灭绝。

We call this a mass extinction event,

我们称之为生物大灭绝，

and although such events may be rare,

尽管这种事件很罕见，

paleontologists have been able to identify several of them

古生物学家已经能从化石记录的

through dramatic changes in the fossil record,

戏剧性改变中鉴定出其中的几个案例。

where lineages that persisted through several geological layers

例如某些物种化石在几个

suddenly disappear.

地质层后突然消失。

In fact, these mass extinctions are used to divide the Earth's history

我们用这些生物大灭绝事件

into distinct periods.

将地球的历史划分为不同的时期。

Although the disappearance of the dinosaurs

虽然恐龙的消失

is the best known mass extinction event,

是最有名的大灭绝事件，

the largest occurred long before dinosaurs ever existed.

但是最大的大灭绝是在恐龙出现之前。

252 million years ago, between the Permian and Triassic periods,

2.52亿年前， 在二叠纪和三叠纪时期之间，

the Earth's land masses gathered together into the single supercontinent Pangaea.

地球上的陆地聚集 成 一个超级大的盘古大陆。

As it coalesced, its interior was filled with deserts,

由于陆地中充满了沙漠，

while the single coastline eliminated many of the shallow tropical seas

在合并的过程，堆积的沙滩湮没了

where biodiversity thrived.

许多生物赖以生息的热带浅海海域。

Huge volcanic eruptions occurred across Siberia,

巨大的火山喷发 横跨整个西伯利亚，

coinciding with very high temperatures,

持续的高温

suggesting a massive greenhouse effect.

造成大规模的温室效应。

These catastrophes contributed to the extinction

这些灾难促成了

of 95% of species in the ocean,

95%的海洋生物的灭绝。

and on land, the strange reptiles of the Permian

陆地上二叠纪的爬行动物

gave way to the ancestors of the far more familiar dinosaurs we know today.

被我们现在熟知的恐龙所取代。

But mass extinctions are not just a thing of the distant past.

然而大规模的生物灭绝并非只是遥远的过去。

Over the last few million years,

在过去的几百万年，

the fluctuation of massive ice sheets at our planet's poles

地球两极巨大的冰层波动

has caused sea levels to rise and fall,

造成了海平面的上升和下降，

changing weather patterns and ocean currents along the way.

以及气候和洋流的变化。

As the ice sheets spread, retreated, and returned,

在冰层蔓延和回退的同时，

some animals were either able to adapt to the changes,

有些动物能够适应这些变化，

or migrate to a more suitable environment.

或迁移去更适合它们的地方，

Others, however, such as giant ground sloths,

但是其余的动物，如巨型地懒、

giant hyenas,

巨鬣狗、

and mammoths went extinct.

和猛犸象则灭绝了。

The extinction of these large mammals

这些巨型哺乳动物的灭绝

coincides with changes in the climate and ecosystem due to the melting ice caps.

与气候和生态系统的变化同步，都是由于冰层融化所致。

But there is also an uncomfortable overlap

另一个双重效应就是

with the rise of a certain hominid species originating in Africa 150,000 years ago.

15万年前某些原于非洲的原始人种的进化。

In the course of their adaptation to the new environment,

在适应新环境的过程中

creating new tools and methods for gathering food and hunting prey,

他们创造新的工具和方法来采集食物和狩猎，

humans may not have single-handedly caused the extinction of these large animals,

人类也许并没有直接造成这些大型动物的灭绝，

as some were able to coexist with us for thousands of years.

因为其中的一些动物和我们共存了数千年。

But it's clear that today,

但是显然今天

our tools and methods have become so effective

我们的捕食工具和方式已经变得如此有效，

that humans are no longer reacting to the environment,

人类不再需要适应自然环境，

but are actively changing it.

而是开始改变自然环境。

The extinction of species is a normal occurrence

物种的灭绝在当今生态系统的

in the background of ecosystems.

大背景下已变成一种正常现象。

But studies suggest that rates of extinction today

但研究显示，

for many organisms

我们今天许多生物的灭绝率

are hundreds to thousands of times higher than the normal background.

高于自然生态灭绝率的几百至几千倍。

But the same unique ability that makes humans capable of driving mass extinctions

人类能够大规模地灭绝生物，

can also enable us to prevent them.

也能用同样的能力来阻止它的发生。

By learning about past extinction events,

通过对物种灭绝的了解，

recognizing what is happening today as environments change,

让我们认识到环境的变化对今天的影响。

and using this knowledge to lessen our effect on other species,

人类正利用这些知识来减少我们对其他物种的影响。

we can transform humanity's impact on the world

我们可以改变人类对自然界的影响

from something as destructive as a massive asteroid

从如小行星撞击地球般的破坏力的转变为

into a collaborative part of a biologically diverse future.

一个和谐共存的生物多样性的未来。