許多瀕臨滅絕的物種有可能未留下化石紀錄就此消失

原始網址：www.sciencedaily.com/releases/2016/03/160321200445.htm

Many species now going extinct may vanish without a fossil trace

Human-made 'sixth extinction' may seem small compared to five prehistoric die-offs

許多瀕臨滅絕的物種有可能未留下化石紀錄就此消失

人類導致的第六次大滅絕規模與前五次史前大滅絕相比看似小了許多

Scientists struggle to compare the magnitude of Earth's ongoing sixth mass-extinction event with the five great die-offs of prehistory. A new study by three paleontologists shows that the species now perishing may vanish without a permanent trace -- and earlier extinctions may be underestimated as well.

科學家力圖比對地球上正在發生的第六次大滅絕和前五次史前大滅絕事件之間的差異。一項由三位古生物學家進行的新研究顯示，現今的瀕危物種可能不留下一絲能保存良久的記錄便就此消失，而我們或許也低估了過往大滅絕事件的規模。

"Comparing the current biodiversity crisis, often called the 'sixth extinction,' with those of the geological past requires equivalent data," says Roy Plotnick, professor of earth and environmental sciences at the University of Illinois at Chicago.

「我們需要對等的資料才能將現今發生的生物多樣性危機，又稱『第六次大滅絕』跟地質史上的其他次滅絕事件互相比較。」芝加哥伊利諾大學的地球與環境科學教授 Roy Plotnick說。

He and two colleagues compared the "Red List" of endangered species with several ecological databases of living species and three paleontological databases of catalogued fossils. They ran a statistical analysis to indicate which threatened species were most likely to disappear with no mark of their existence.

他和另外兩外同僚比對了編列瀕危物種的「紅皮書」(Red List)、數個紀錄現存動物的生態資料庫，以及三個記載已編目化石的古生物資料庫。接著他們進行統計分析以找出哪些受威脅的物種最有可能不留下牠們曾經存在的痕跡而永遠消失。

The researchers were shocked to find that more than 85 percent of the mammal species at high risk of extinction lack a fossil record. Those at highest risk have about half the probability of being incorporated into the fossil record compared to those at lower risk.

研究人員相當驚訝地發現高度瀕危的哺乳類物種中有85%以上會缺乏化石紀錄。面臨最高瀕危風險的物種成為化石紀錄一部分的機率，比那些處在較低風險的物種形成化石的機率低了一半。

Animals least likely to be found as fossils are "the small, cute and fuzzy ones, like rodents and bats," Plotnick said. "Body size is an obvious factor -- bigger things tend to leave a fossil record, as do things with larger geographical ranges."

動物中最難發現的化石便是那些「小巧可愛、毛茸茸的動物，像是齧齒類和蝙蝠」。 Plotnick說。「體型是相當明顯的要素，大型物種比較容易留下化石紀錄，而那些地理分布比較廣的也是。」

Viewed from the perspective of the fossil record alone, the magnitude of the current mammal die-off thus appears markedly reduced. The picture may be even more distorted for other land-dwelling vertebrates: only 3 percent of today's threatened bird species and 1.6 percent of threatened reptile species have a known fossil record.

若僅由化石紀錄的觀點來看，當今哺乳類的滅絕規模會顯得輕微了許多。對於其他陸生脊椎動物而言，從同樣的觀點出發可能會更加曲解牠們面臨的滅絕困境。今日備受威脅的鳥類中只有百分之3留下了為人所知的化石紀錄；而爬蟲類更是只有百分之1.6。

Comparing the scale of the current extinction episode, which is based primarily on terrestrial vertebrates, to earlier extinctions that are mostly calculated from the fossil record of hard-shelled marine invertebrates, is particularly problematic, Plotnick said, although ancient extinctions may also be underestimated by contemporary paleontologists.

Plotnick說現行的滅絕事件主要對象是陸生脊椎動物，然而過去滅絕事件的規模大多是利用具有硬殼的海生無脊椎動物化石紀錄來估算，因此要比較兩者的規模就會特別有問題。而現代的古生物學家也可能低估了古代滅絕事件的規模。

Nevertheless, fossils will provide the only reliable record of life on Earth for posterity.

然而，化石終究是地球生命留給後裔的紀錄中唯一可靠的。

"There are species going extinct today that have never been described," Plotnick said. "Others are going extinct that are known only because someone wrote it down." All such species would thus be unknown in the far future, he said, if the written historical record is lost -- as it might well be.

「今日許多邁向滅亡的物種是人們從來沒有記述到的。」 Plotnick說。「而其他消失的物種能夠為人所知僅僅是因為有人將牠書寫下來。」如果這些歷史文字紀錄消失，那麼所有這類物種在遙遠的未來都將被淡忘，而這確實很有可能發生，他說。

The fossil record, Plotnick points out, is much more durable than any human record.

Plotnick指出化石紀錄遠比人類所有的紀錄方式禁得起時間考驗。

"As humanity has evolved, our methods of recording information have become ever more ephemeral," he said. "Clay tablets last longer than books. And who today can read an 8-inch floppy?" he shrugged. "If we put everything on electronic media, will those records exist in a million years? The fossils will."

「隨著人類的進步，我們保存資訊的方式卻顯得越來越稍縱即逝。」他說。「泥片(clay tablet，巴比倫人將文字刻於其上)可以比書本流傳的更久。而今日又有誰能讀取8吋磁碟片？」他聳聳肩。「如果我們將所有事物都保存在電子裝置中，這些檔案可以存在百萬年之久嗎？無庸置疑的是化石絕對可以。」

Other authors on the study, published earlier this month in Ecology Letters, are Felisa A. Smith of the University of New Mexico and S. Kathleen Lyons of the National Museum of Natural History in Washington, D.C.

此篇本月稍早刊登於《生態學通訊》的論文的其他作者還包括了新墨西哥州大學的 Felisa A. Smith，以及華盛頓國立自然歷史博物館的 S. Kathleen Lyons。

引述自：University of Illinois at Chicago. "Many species now going extinct may vanish without a fossil trace: Human-made 'sixth extinction' may seem small compared to five prehistoric die-offs." ScienceDaily. ScienceDaily, 21 March 2016.