Enlisting Beetles Where Trees are Pests
徵召甲蟲對付有害樹種
By Ken Belson

LEES FERRY, Arizona – In this corner of America known for its vast landscapes, rugged mountains and deep river canyons, signs of the havoc created by the minuscule tamarisk beetle are everywhere.
在以視野遼闊、山脈起伏與河谷高深著稱的美國亞利桑納州李斯渡口（編按；大峽谷的起點），檉柳甲蟲肆虐的痕跡隨處可見。

For stretches along the banks of the Colorado River, hundreds of tamarisk trees – also known as salt cedars – are gray and withered. Their parched branches look like victims of fire or drought.
在科羅拉多河兩岸的部分地區，數百棵又稱紅荊的的檉柳呈灰色已經枯萎。它們的樹枝已經乾枯，彷彿火災或乾旱的受害者。

But this is not the story of beloved trees being ravaged by an invasive pest. Farmers, ranchers and the water authorities here are eager to get rid of the tamarisk trees, which are not native to Arizona and which they say suck too much water.
然而這不是人們鍾愛的樹木被外來害蟲蹂躪的故事。當地的農民、牧場經營者與水資源當局急於剷除這些吸收太多水分的非本土樹種。

They have welcomed the beetles, which have made their way from Colorado and Utah over the last decade, and have watched as the centimeter-long workhorses have damaged the trees by eating their spindly leaves. The hope is that the beetles will now rid Arizona of the trees.
他們歡迎過去10年自科羅拉多州與猶他州一路而來的甲蟲，看著體長僅一公分的牠們啃食檉柳的細長葉子，使檉柳受到重創。他們希望甲蟲能夠替亞利桑納州除掉這種樹。

“We view the tamarisk as a pest,” said Joseph Sigg, of the Arizona Farm Bureau.
亞利桑納州農業局的席格說：「我們把檉柳視為有害的樹種。」

But scientists say that nature is rarely a zero-sum game, and that removing the deep-rooted tamarisks – which the authorities have tried with bulldozers, chain saws and now beetles – will not produce more water. New tamarisks or other trees will replace the fallen ones, the scientists say, and the birds that live in the tamarisks, like the endangered Southwestern willow flycatcher, will be harmed.
當局曾經嘗試以推土機、電鋸與如今的甲蟲對付這些檉柳。然而科學家表示，大自然不是零和遊戲，剷除這些扎根很深的樹不會使水量增加，新的檉柳或其他樹木會取而代之，以檉柳為家的鳥類，如瀕危的西南柳樹鶲，必然受害。

Plus, once the beetles are done eating tamarisk leaves, they are likely to feed on other trees.
還有，啃完檉柳的葉子之後，這些甲蟲可能繼續啃食其他樹木。

Ruinous droughts and rapid population growth in recent years have strained the state’s vulnerable water supply and heightened the scramble to find new solutions, from desalination to cloud seeding to vegetation management, which includes eliminating the tamarisk.
近年來的多次嚴重乾旱與人口快速增加導致該州原已不足的水供應更加吃緊，促使有關方面加緊尋找其他對策，包括去鹽化、人工造雨與植被管理，其中包括消除檉柳。

The tamarisk, which lives in Asia and the Middle East, was imported more than a century ago to prevent erosion. With a dense and sprawling network of roots and an ability to thrive in arid terrain, the tree did that job well.
當地人為了防止土壤侵蝕而於100多年前引進原產於亞洲與中東的檉柳。它們根部濃密，蔓延面積大，可在不毛之地存活，充分發揮了作用。

But as rivers were dammed, riverbanks receded, starving many native trees and pushing out the insects, birds and other wildlife that relied on them. In their place, the tamarisk took over.
然而隨著河流築壩，河岸為之倒退，導致本地樹木枯死，仰賴它們的昆蟲、鳥類與其他野生動物遷至他處。檉柳取而代之。

Advocates of removing the tamarisk claim that a mature tree can consume more than 750 liters of water a day.
主張剷除檉柳的人說，一棵成熟的檉柳每天可消耗逾750公升的水。

There is little proof, though, that removing the tamarisk will increase the amount of available water. And if thirstier trees replace it, there could be even less water.
不過並無具體證據足證，剷除檉柳會使可用的水增加，而如果被更會喝水的樹木取代，可用的水將更少。

While the beetle appears to be efficient at defoliating tamarisk trees, it works on its own schedule, which is why the tree is still often removed manually. It is a costly and imperfect process.
甲蟲似可有效啃掉檉柳葉，卻有自己的作息時間表。因此檉柳經常還是須以人力移除。這麼做很花錢，效果也不理想。

To save money and avoid the constant culling, the United States Department of Agriculture studied how to introduce the tamarisk beetle, the tree’s natural predator. About a decade ago, the first beetles were released in Colorado, and despite predictions that they would move slowly, they have arrived in Northern Arizona sooner than expected.
為了省錢與避免必須不斷移除，美國農業部開始研究如何引進檉柳的天敵甲蟲。大約10年前，在科羅拉多州釋放了第一批甲蟲。雖然當局預期牠們移動速度會很緩慢，牠們卻提早抵達了亞利桑納州北部地區。

The beetles are likely to reach the southern parts of Arizona in about two years, said Stacy Beaugh of the Tamarisk Coalition, which restores riversides. “It hasn’t been overnight, but it’s been much faster than expected,” she said.
檉柳聯盟專門復育河畔，成員史黛絲．畢奧格表示，這些甲蟲可能兩年後就會抵達亞利桑納州南部。她說：「不是一夜之間就來到，卻比預期快許多。」

On this stretch of the Colorado River near the Grand Canyon National Park, the beetles’ handiwork is evident. But the trees’ roots are so dense that it may take several seasons before they die, said Gibney Siemion, an ecologist with the Grand Canyon Wildlands Council, which spent about $24,000 to remove the trees.
在鄰近大峽谷國家公園的科羅拉多河李斯渡口河段，甲蟲的工作成果明顯可見。不過大峽谷荒野協會的生態專家塞米恩表示，由於檉柳的根部實在太密，可能幾季之後才會枯死。該協會曾以2.4萬美元的經費移除檉柳。

Kelly Burke of the Council said that 15 people spent 10 days cutting tamarisks from a two-hectare slice of shoreline 14 kilometers downriver from the Glen Canyon Dam. They applied Garlon, a herbicide, to the stumps, and the fallen trees were burned.
協會的凱莉．柏克表示，協會委託15人以10天的時間，砍除葛蘭峽谷大壩下游14公里處2公頃岸線地帶的檉柳。他們對殘幹施用「賈農」除草劑，同時燃燒倒下的檉柳。

Yet nearly five years later, tamarisk saplings have sprouted next to the blackened stumps, a reminder of how difficult it is to remove a tree that produces hundreds of millions of seeds.
然而將近五年之後，檉柳的幼樹在焦黑殘幹旁快速成長，證明要剷除可產生無數種子的檉柳何其困難。

“You’ll never get the last tree,” Ms. Siemion said. “You do your best, but the tamarisk is very adaptable.”
塞米恩說：「你永遠不可能砍到最後一棵檉柳。你盡力而為，檉柳卻有很強的適應力。」

原文參照：
http://www.nytimes.com/2014/07/15/us/arizona-water-tamarisk-beetle.html

2014-07-29聯合報/G9版/UNITEDDAILYNEWS 陳世欽譯 原文參見紐時週報七版右