What happens when continents collide? - Juan D. Carrillo

譯者: Isabel Lin 審譯者: 庭芝 梁

Tens of millions of years ago,

數千萬年前，

大自然的力量造成了兩大板塊 一場無可避免的撞擊歷程，

a force of nature set two giant masses on an unavoidable collision course

that would change the face of the Earth

這場歷程將改變地球的面貌，

and spell life or death for thousands of species.

並且決定成千上萬物種的 生存與滅亡。

The force of nature was plate tectonics,

這股自然之力源自板塊構造，

and the bodies were North and South America.

而這兩大板塊， 正是北美洲和南美洲。

And even though they were hurdling towards each other

即使它們以毫不起眼， 每年移動 2.5 公分的速度，試圖跨越對方，

at an underwhelming 2.5 cm per year,

their collision actually did have massive biological reprocussions

這場撞擊卻因此引發了一場 地球史上最大的生物移徙事件，

by causing one of the greatest episodes of biological migration in Earth's history:

並且實際上造成了 生物學上的巨大影響：

The Great American Biotic Interchange.

南、北美洲生物大遷徙。

Our story begins 65 million years ago, the beginning of the age of mammals,

我們的故事要從六千五百萬年前， 哺乳動物的出現說起，

when what is now North and South America

當時，現今的南、北美洲 還是完全分開的板塊，

were continents separated by a marine connection

中間隔著一片海域，則是連接著 太平洋和大西洋。

between the Pacific and Atlantic Oceans.

在這段期間， 居住在南美洲的物種，

During this time, South America was the home of fauna

that included armored glyptodonts as large as compact cars,

包括全身披著厚甲的雕齒獸， 體型與小型車一樣大；

giant ground sloths weighing more than a ton,

以及巨型地懶， 重量超過一公噸；

opossums, monkeys, and carnivorous terror birds.

此外還有負鼠、猴子， 以及肉食駭鳥。

North America had its own species,

在北美洲，也有自己的物種，

such as horses, bears, and saber-toothed cats.

例如馬、熊，和劍齒虎。

Over 20 million years, the shifting of the Farallon and Caribbean Plates

在二千萬年前，"法拉隆" 與 "加勒比" 兩個板塊的位移，

produced the Central America Volcanic Arc, a peninsula connected to North America,

形成了一個連接北美洲的 中美火山弧半島，

with only a very narrow seaway separating it from South America.

與南美洲之間， 僅僅相隔一道狹窄的海道，

As these plates continued to surf the Earth's magma layer

由於這些板塊持續延伸至

太平洋板塊下深處的地球岩漿層，

far beneath the Pacific Ocean floor,

the Caribbean Plate migrated eastward,

加勒比板塊向東位移，

並在大約一千五百萬年前

and about 15 million years ago,

South America finally collided with this Central American Arc.

南美陸塊撞上了中美洲島弧。

這逐漸關閉了太平洋 和加勒比海之間的水路連結，

This gradually closed the water connection between the Pacific and the Caribbean,

creating a land bridge,

並且形成一座陸橋，

which connected North America to South America.

連接北美洲和和南美洲。

陸生生物現在可以橫越兩大洲間，

Terrestrial organisms could now cross between the two continents,

從化石記錄看來，

and from the fossil records,

it's evident that different waves of their dispersals took place.

當時明顯出現了 好幾次的生物播遷。

Even though plants don't physically move,

儘管植物不會自己移動，

they are easily dispersed by wind and waves,

它們很容易藉由風和海浪擴散，

so they migrated first, along with a few species of birds.

因此，它們跟著一些鳥類 最先開始遷徙；

They were followed by some freshwater fishes

接著是一些淡水魚類 和兩棲動物，

and amphibians,

and finally, various mammals began to traverse the bridge.

最後，各種哺乳動物 開始橫越此陸橋。

From South America, mammals like ground sloths and glyptodonts

從南美洲來的哺乳動物， 例如地懶和雕齒獸，

were widly distributed in North America.

廣泛散佈到北美洲。

Moreover, many South American tropical mammals,

此外，許多南美熱帶哺乳動物，

like monkeys and bats, colonized the forests of Central America,

例如猴和蝙蝠， 定居於中美洲的森林中，

至今也大量繁衍。

and are very abundant today.

South American predator marsupials went extinct 3 million years ago,

在南美洲，一種有袋類的掠食動物 於三百萬年前絕種了，

at which point North American predators, such as cats, bears and foxes,

此時北美洲的掠食者， 例如貓科動物、熊和狐狸，

migrated south and occupied the ecological space left behind.

向南遷徙，並佔據了 留下來的生態環境。

Horses, llamas, tapirs, cougars, saber-toothed cats, gomphotheres,

馬、大羊駝、貘、美洲獅、 劍齒虎、嵌齒象，

and later humans also headed south across the land bridge.

和之後的人類， 也往南越過了此陸橋。

But what happened on land is only half the story.

但是，在陸地上發生的一切 僅僅是是半個故事。

What had been one giant ocean was now two,

這裡曾是一片海洋， 現在被一分為二，

creating differences in temperature and salinity for the two bodies of water.

造成這兩個水域 具有不同溫度和鹽度。

The isthmus also became a barrier for many marine organisms,

這地峽也成為 許多海洋生物的屏障，

like mollusks, crustaceans, foraminifera, bryozoans, and fish,

例如軟體動物、甲殼類動物、 有孔蟲、苔蘚蟲、還有魚類，

and separated the populations of many marine species.

並隔開了許多海洋生物群。

It also allowed the establishment of the thermohaline circulation,

地峽也使得 溫鹽環流得以形成，

a global water conveyor belt,

這一條全球水路輸送帶，

which transports warm water across the Atlantic,

運送溫水橫過整個大西洋，

and influences the climate of the East Coast of North America,

並且影響北美洲東海岸、

歐洲西岸，和其他 許多地區的氣候。

the West Coast of Europe, and many other areas.

It's a challenge to track all of the ways

想要追蹤所有 因為美洲陸塊撞擊

the collision of the Americas changed the world,

而造成世界的改變， 是一項艱困的挑戰。

但我們可以肯定地說：

but it's safe to say that the ripples of the Great American Biotic Interchange

南北美洲生物大遷徙 造成的連鎖反應

have propagated through the history of life on the planet,

已遍佈於地球和人類的生命史。

and that of mankind.

倘若這些生物沒有絕種，

What if these species hadn't gone extinct,

or if there were no monkeys in Central America,

或是中美洲沒有出現猴子，

or jaguars in South America?

或是南美洲沒有出現美洲虎？

What if the thermohaline circulation wasn't flowing?

倘若溫鹽環流沒有流動，

Would the East Coast of North America be much colder?

那麼北美洲的東海岸會冷得多嗎？

It all goes to show some of the most impactful transformations of our planet

這一切都顯示出 我們地球上最具衝擊的轉變，

aren't the explosive ones that happen in an instant,

不是發生在爆炸性的瞬間，

but the ones that crawl towards irreversible change.

而是一種徐徐前進， 不可逆的轉變。

We are the product of history.

我們就是歷史的產物。