Are We Facing the Sixth Mass Extinction?
Many scientists think we're now in the middle of a mass extinction event.
Is this true and will we survive?
First of all, let's define what a mass extinction event is.
It's a large die-off of species and it's only happened five or six times in the 4 billion year history of life on this planet.
The most famous extinction event happened 65 million years ago when an asteroid struck what's now the Yucatan Peninsula in Mexico.
The asteroid kicked up a lot of dust, creating a shift in climate and wiping out the dinosaurs and many other species.
Of course, this event had a happy ending for us because it killed off the big reptiles and created space for mammals and ultimately, humans.
We may not be so lucky next time.
Mass extinction events can wipe out as many as 90 percent of all species.
Humans would most certainly not survive an event of that magnitude.
But there's no iron-clad proof that we're in a mass extinction event now.
The only thing we know about past extinction events is what we see in the fossil record.
translation
sentence:
许多科学家认为我们现在正处于大规模灭绝事件中。
这是真的吗?我们能活下来吗?
首先，让我们定义一下什么是大规模灭绝事件。
这是一次大规模的物种灭绝，在地球40亿年的生命历史中只发生过五六次。
最著名的灭绝事件发生在6500万年前，当时一颗小行星撞击了现在的墨西哥尤卡坦半岛。
这颗小行星扬起了大量的灰尘，造成了气候的变化，恐龙和许多其他物种灭绝。
当然，这一事件对我们来说有一个美好的结局，因为它杀死了大型爬行动物，为哺乳动物创造了空间，最终为人类创造了空间。
我们下次可能就没这么幸运了。
大规模灭绝事件可以消灭多达90%的物种。
人类肯定无法在这种规模的事件中幸存下来。
但没有确凿的证据表明我们现在正处于大规模灭绝事件中。
我们对过去灭绝事件的唯一了解是我们在化石记录中看到的。
Even though today, we're losing, by some estimates, 200 species a day, that still doesn't add up to what we know happened in the past.
The passenger pigeon is a case in point.
It once numbered in the billions in North America and is now extinct.
But there are only two known examples of this species in the fossil record.
What has scientists worried, though, is a similarity between what's happening now and what we see in past extinction events.
For example, the Permian Extinction Event, about 250 million years ago, was started by a massive volcanic eruption in what is now Siberia.
Lava vaporized a huge cold deposit, causing a spike in carbon emissions on the order of what we're seeing today.
Another example is the Great Oxygenation Event of 2.4 billion years ago.
Here, cyanobacteria, a precursor to modern-day plants, began emitting oxygen, gassing much of the anaerobic bacteria into oblivion.
We're currently changing Earth's atmospheric chemistry in similarly large ways.
Only time will tell if we're causing another mass extinction.
translation
sentence:
即使在今天，据估计，我们每天失去200个物种，这仍然与我们所知道的过去发生的事情不相符。
旅鸽就是一个很好的例子。
它曾经在北美有数十亿只，现在已经灭绝。
但在化石记录中，这种物种只有两个已知的例子。
然而，科学家们担心的是，现在发生的情况与我们在过去的灭绝事件中看到的情况有相似之处。
例如，大约2.5亿年前的二叠纪大灭绝事件是由现在西伯利亚地区的一次大规模火山爆发引发的。
熔岩蒸发了一个巨大的冷沉积物，导致碳排放量激增，就像我们今天看到的那样。
另一个例子是24亿年前的大氧化事件。
在这里，蓝藻，现代植物的前身，开始释放氧气，使大部分厌氧菌消失。
我们目前正在以类似的大规模方式改变地球的大气化学。
只有时间才能证明我们是否正在造成另一次大灭绝。
vocabulary
[
{
"name": "mass",
"trans": [
"n. 质量；群众；大量；块",
"v. 聚集；集结",
"adj. 大批的；数量极多的；广泛的"
],
"usphone": "'mæs'",
"ukphone": "''"
},
{
"name": "extinction",
"trans": [
"n. 灭绝，消亡；（债务的）偿清；消光"
],
"usphone": "'ɪkˈstɪŋkʃ(ə)n'",
"ukphone": "''"
},
{
"name": "first of all",
"trans": [
"首先；首要；是首先的意思"
],
"usphone": "''",
"ukphone": "''"
},
{
"name": "asteroid",
"trans": [
"n. 小行星；海星",
"adj. 星状的；类似海星的"
],
"usphone": "'ˈæstərɔɪd'",
"ukphone": "''"
},
{
"name": "struck",
"trans": [
"adj. <英，非正式>对……印象很好（be **** on sb./sth.）；受罢工影响的",
"v. 打，撞；（用手或武器等）打；（使）碰撞（strike 的过去式和过去分词）"
],
"usphone": "'strʌk'",
"ukphone": "''"
},
{
"name": "kick up",
"trans": [
"激起; 引起骚动; 显示混乱; 挑起",
"na. 踢起(灰尘)；引起(骚动)"
],
"usphone": "'kɪk ʌp'",
"ukphone": "''"
},
{
"name": "wipe",
"trans": [
"v. 擦；抹；拭；消除",
"n. 擦；拭；揩；（湿）抹布"
],
"usphone": "'waɪp'",
"ukphone": "''"
},
{
"name": "wipe out",
"trans": [
"na. 擦去；【无线】遮蔽；遮蔽地域；【信】封闭",
"消灭；消除"
],
"usphone": "''",
"ukphone": "''"
},
{
"name": "reptile",
"trans": [
"n. 爬行动物；（非正式）卑鄙的人",
"adj. 爬行动物的"
],
"usphone": "'ˈreptaɪl'",
"ukphone": "''"
},
{
"name": "as many as",
"trans": [
"prep. …和…一样多",
"多达；和……一样多；像……一样多"
],
"usphone": "''",
"ukphone": "''"
},
{
"name": "magnitude",
"trans": [
"n. 巨大，重要性；震级；规模，大小；数量，数值；（恒星的）亮度，星等"
],
"usphone": "'ˈmæɡnɪtuːd'",
"ukphone": "''"
},
{
"name": "iron-clad",
"trans": [
"adj. 装甲的；不可改变，打不破的",
"n. 铁甲舰，装甲舰"
],
"usphone": "''",
"ukphone": "''"
},
{
"name": "ironclad proof",
"trans": [
"铁证：指无可辩驳、确凿的证据。"
],
"usphone": "''",
"ukphone": "''"
},
{
"name": "fossil",
"trans": [
"adj. 化石的，从地下采掘出的；不变的，古老的",
"n. 化石；<非正式>思想僵化的人；僵化的事物"
],
"usphone": "'ˈfɑːs(ə)l'",
"ukphone": "''"
},
{
"name": "add up to",
"trans": [
"na. 总计共达；〔口语〕总之就是",
"网络. 合计达；合计为；意味着"
],
"usphone": "'æd ʌp tu'",
"ukphone": "''"
},
{
"name": "passenger pigeon",
"trans": [
"na. (能飞长距离的)北美候鸽",
"旅鸽；侯鸽；北美旅鸽"
],
"usphone": "''",
"ukphone": "''"
},
{
"name": "once",
"trans": [
"adv. 曾经，一度；任何一次，从来；乘以一；一次， 一回；",
"conj. 一.....就， 一旦",
"n. 一次"
],
"usphone": "'wʌns'",
"ukphone": "''"
},
{
"name": "numbered",
"trans": [
"adj. 编号的；有限的；时日无多的；计数的",
"v. 总计；包含；编号；把……算作（**** 的过去式和过去分词）"
],
"usphone": "'ˈnʌmbərd'",
"ukphone": "''"
},
{
"name": "similarity",
"trans": [
"n. 相似性；相似点，类似的地方"
],
"usphone": "'ˌsɪməˈlærəti'",
"ukphone": "''"
},
{
"name": "Permian",
"trans": [
"adj. 二叠纪的",
"n. 二叠纪；二叠纪岩；二叠统"
],
"usphone": "'ˈpɜːrmiən'",
"ukphone": "''"
},
{
"name": "eruption",
"trans": [
"n. 喷发；（战争、怒气等的）爆发；发疹"
],
"usphone": "'ɪˈrʌpʃ(ə)n'",
"ukphone": "''"
},
{
"name": "vaporized",
"trans": [
"vi. 蒸发",
"vt. 使……蒸发"
],
"usphone": "'ˈveɪpəraɪz'",
"ukphone": "''"
},
{
"name": "deposit",
"trans": [
"v. 放下，放置；储蓄；存放，寄存；沉积，沉淀；支付（押金、订金或预缴费用）",
"n. 沉积物，沉积层；订金；押金；存款；竞选保证金"
],
"usphone": "'dɪˈpɑzɪt'",
"ukphone": "''"
},
{
"name": "spike",
"trans": [
"n. 穗；穗状花序；猛增；尖状物",
"v. 用尖物刺入（或扎破）；在…中偷偷掺入（烈酒、毒药或毒品）"
],
"usphone": "'spaɪk'",
"ukphone": "''"
},
{
"name": "emission",
"trans": [
"n. 排放物，散发物；（尤指光、热、气等的）散发，排放；射精，遗精；<古>发行"
],
"usphone": "'ɪˈmɪʃ(ə)n'",
"ukphone": "''"
},
{
"name": "oxygenation",
"trans": [
"n. 以氧处理，氧化作用"
],
"usphone": "'ˌɑːksɪdʒəˈneɪʃn'",
"ukphone": "''"
},
{
"name": "cyanobacteria",
"trans": [
"n. 蓝藻细菌；蓝藻目"
],
"usphone": "'saɪænɒ'bæktɪərɪə'",
"ukphone": "''"
},
{
"name": "precursor",
"trans": [
"n. （事物）先驱，先兆；（尤指经新陈代谢形成另一种物质的）前体，前质"
],
"usphone": "'priˈkɜːrsər'",
"ukphone": "''"
},
{
"name": "anaerobic",
"trans": [
"adj. [微] 厌氧的，[微] 厌气的；没有气而能生活的"
],
"usphone": "'ˌænəˈroʊbɪk'",
"ukphone": "''"
},
{
"name": "oblivion",
"trans": [
"n. 遗忘；湮没；赦免"
],
"usphone": "'əˈblɪviən'",
"ukphone": "''"
},
{
"name": "atmospheric",
"trans": [
"adj. 大气（层）的，有关大气的；有神秘（美）感的，富有情调的"
],
"usphone": "'ˌætməsˈfɪrɪk'",
"ukphone": "''"
}
]