by Christopher Joyce

Walking through the Atlantic coastal forests of Brazil in the morning is like eavesdropping[偷聽] on a toucan[巨嘴鳥] symphony[交響曲]. Each produces its own unique sound to cut through the auditory[聽覺的] clutter[混亂]. But over the past century， the toucans have been disappearing. Hunting， farming， logging[伐木]—its all taken a big toll[產(chǎn)生負(fù)面影響] on toucans.

With fewer and fewer birds， the toucan symphony is down to a murmur[低語(yǔ)]. Theyre just about gone from many parts of the forest. And it appears that their disappearance kickstarted[（比喻）強(qiáng)勁推動(dòng)] a whole evolutionary[進(jìn)化的] change in the forest itself， particularly in its palm trees.

According to research in the journal Science， this is what happened. The dominant[占優(yōu)勢(shì)的] palm tree depends on birds to eat its fruit and then defecate[通便] the seeds somewhere， so it will germinate[發(fā)芽] and grow a new tree.

Mauro Galetti is a biologist at the Estadual Paulista University in Brazil. He says toucans play a big part in this reproductive[生殖的] process[過(guò)程].

Mauro Galetti： These large birds， they have an extremely important role in the forest not only because they disperse[散播] seeds， but because they disperse large seeds.

The largest palm seeds， some the size of marbles[彈球]， are too big for most birds to eat except for those big-mouthed toucans. So as the toucans disappeared， the palms that made big seeds were out of luck—no seed dispersers[分散器]. Meanwhile， the palms that were

genetically[從遺傳學(xué)角度] disposed[處理] to make small seeds did just fine； in fact， they thrived[茁壯成長(zhǎng)] and started to dominate[占優(yōu)勢(shì)] the forest. Galetti： The extinction[滅絕] of large birds changed the evolution of this palm.

Now， humans have always been messing with[干擾] nature. When we cut down forests or prairie[大草原]， or when we over-hunt， we change the mix of plants and animals. But in this case，humans actually altered[改變] the genetic makeup[組成] of a wild palm tree population， in just a century， by accident.

So what happens if these small-seed palms eventually[最后] take over？ Well， it turns out that smaller seeds arent so good. They dry up and die faster in hot， dry weather. And scientists predict[預(yù)言] that climate change will make parts of Brazil hotter and drier， so much so that these palms could be in trouble.

Galetti： The impacts[沖擊] on the forest can be quite dramatic[戲劇性的] because several animal species[種類] depends， rely on this palm for food.

About 60 species of animals， in fact. So the take-home[實(shí)際得到的] message is： As the toucan goes， so goes the forest.

晨間在巴西的大西洋沿岸森林中漫步，就像無(wú)意中聽見巨嘴鳥的交響樂(lè)一樣。每一只巨嘴鳥都有自己獨(dú)特的叫聲，在嘈雜紛繁的大合奏當(dāng)中清晰可辨。但是在過(guò)去一個(gè)世紀(jì)以來(lái)，巨嘴鳥的數(shù)目不斷減少。人類的獵殺農(nóng)耕以及大肆伐木都對(duì)巨嘴鳥產(chǎn)生了極大的危害。

隨著鳥群不斷縮減，巨嘴鳥大合唱逐漸變成了呢喃細(xì)語(yǔ)。林中各處如今都看不見它們的身影了。而巨嘴鳥的消失似乎觸發(fā)了森林本身的演變——尤其體現(xiàn)在棕櫚樹（的變化）上。

《科學(xué)》雜志上的研究指出，事情是這樣的：大多數(shù)棕櫚樹依賴?guó)B類吞食果實(shí)，隨后在其他地方將種子排出，這樣種子就能（在別的地方）發(fā)芽生根，長(zhǎng)成一棵新的樹苗。

莫羅·加萊蒂是巴西圣保羅州立大學(xué)的生物學(xué)家。他說(shuō)巨嘴鳥在這個(gè)繁衍過(guò)程中充當(dāng)了非常重要的角色。

莫羅·加萊蒂：這些大型鳥類在森林當(dāng)中占據(jù)著相當(dāng)重要的地位，因?yàn)樗鼈儾粌H傳播種子，傳播的還是大顆的種子。

最大的棕櫚樹種子有些大如彈珠，大多數(shù)鳥類無(wú)法下咽，只有巨嘴鳥可以吞下去。所以隨著巨嘴鳥的消失，出產(chǎn)大種子的棕櫚樹就不走運(yùn)了——它們失去了播種者。與此同時(shí)，那些在遺傳上更容易長(zhǎng)出小種子的棕櫚樹則一切如常；事實(shí)上，它們生機(jī)勃勃地壯大起來(lái)，開始逐步占領(lǐng)森林。

加萊蒂：大型鳥類的滅絕改變了這種棕櫚樹的演化過(guò)程。

人類向來(lái)對(duì)大自然肆意妄為。當(dāng)我們不斷砍伐森林，破壞草原，或者過(guò)度捕獵，我們就會(huì)改變（當(dāng)?shù)氐模﹦?dòng)植物構(gòu)成。不過(guò)在這個(gè)例子當(dāng)中，僅僅是一個(gè)無(wú)意的行為，人類便在一百年間改變了一個(gè)國(guó)家的野生棕櫚樹群的遺傳結(jié)構(gòu)。

如果這些小種子棕櫚樹徹底占領(lǐng)了森林，那會(huì)發(fā)生什么事情呢？事實(shí)上，小種子并不好。它們?cè)诟稍锟釤岬奶鞖饫锶菀赘砂T，壽命更短?？茖W(xué)家預(yù)言，由于氣候變化，巴西多處將會(huì)變得更加炎熱，更加干燥，這種劇烈的變化將會(huì)給這些棕櫚樹帶來(lái)極大的麻煩。

加萊蒂：森林（系統(tǒng)）可能會(huì)受到很嚴(yán)重的影響，因?yàn)樽貦皹涫呛脦追N動(dòng)物的食物來(lái)源。

事實(shí)上，（這將影響到）將近60種動(dòng)物。所以（這件事的）實(shí)際結(jié)論就是：巨嘴鳥沒了，森林也沒了。