2008年12月9日 星期二

海洋酸化、噪音 鯨魚日子難熬

海洋酸化、噪音 鯨魚日子難熬

環境資訊中心
http://e-info.org.tw/node/39543

摘譯自2008年12月3日ENS義大利,羅馬報導;葉松剛編譯;蔡麗伶、禾引審校

白鯨;圖片來源:Jenny Spadafora由野生生物團體組成的聯盟12月3日表示,越來越多的船艦、油氣探勘震波、鄰海建築與遊憩、新式軍用聲納等,使得海洋日趨嘈雜。聯盟警告,以聲音作為溝通媒介、搜索食物以及尋找伴侶的海洋哺乳動物會因此受到更大的威脅。

該聯盟出席了在羅馬由聯合國環境規劃署(UNEP)舉辦的遷徙物種研討會(CMS),於會中呼籲政府與企業應為船隻安裝更安靜的引擎,進行震波探勘時應採用更嚴謹的規範,並讓海軍利用更新、低干擾的聲納技術。

國際野生動物保護組織(IFAW) 在研討會中提出一篇名為〈海洋噪音:降低音量〉(Ocean Noise: Turn it Down)的報告,內容指出噪音增加的程度導致藍鯨能夠溝通的距離減少了90%。根據報告的估算,過去40年間,行駛在太平洋的船隻所製造的噪音每十年就會倍增。全球航運船隊的數量繼1965至2003年間成長一倍之後,預計將在2025年再增加一倍。在震波探勘中使用的空氣槍會產生巨大聲響,音量高峰值達到259分貝,每10秒就產生一次,過程長達數月之久,傳播距離超過3000公里。報告中指出世界上有超過90艘的震波探勘船,其中有1/4終年運行。此外,全球估計有300座海軍用聲納系統,產生超過235分貝壓力音波。如此巨大的聲響,比一般認為對人類安全的145分貝還要強十億倍以上。野生生物團體的律師法蘭克(Veronica Frank)表示:「我們需要大規模的行動,其中包含一項規範:超大型油輪以下,所有船隻的製造商與業主應該與國際間有能力的團體進行合作,將噪音減量方法一開始就列入船艦的設計與運作之中。」

海洋越來越嘈雜的消息也伴隨著新的隱憂:溫室氣體二氧化碳的增加,可能使得水面下的噪音程度更為嚴重。美國蒙特利灣水族研究中心的研究人員在10月份發表的報告中指出,海洋酸度的增加將使海洋環境更吵雜。由跨政府氣候變遷委員會(IPCC)提出的保育計畫內容表示,到2050年時,海水中的化學性質可能會增加0.3個pH值。2008年10月1發刊的《地球物理研究通訊》(Geophysical Research Letters)中,蒙特利灣的赫斯特(Keith Hester)與同事估計,到了2050年海洋酸度的改變可能會讓聲音在水面下傳播的距離再增加70%。赫斯特與他的團隊表示,海水越酸,中低頻音被吸收的量越少。海水化學性質的改變也許意謂著,今日海水吸收低頻音的能力比工業革命之前減少了10%。

大翅鯨;圖片來源:NOAA赫斯特還表示,除非減少溫室氣體的排放-這同時是本周在波蘭波茲南(Poznan)舉辦年度聯合國氣候會議的重要議題-海洋酸度的提升將會增加海中的背景音量,同時可能對海洋哺乳動物的行為造成影響。

鯨豚保育協會(WDCS)科學部門主任西蒙(Mark Simmonds)在羅馬舉行的遷徙物種研討會(CMS)中表示:「全世界許多海洋的水面下,人類製造的噪音已產生了一種聽覺瘴霧與不和諧的聲響。」

西門表示現在有越來越多的證據,證明水面下巨大聲響與一些海洋哺乳動物的集體擱淺有關,尤其是深潛的喙鯨。當鯨豚受到巨響驚嚇,牠們會表現出不尋常的潛水行為,罹患與人類潛水員相似的潛水夫病。

Noisy, Acid Oceans Increasingly Harmful to Whales
ROME, Italy, December 3, 2008 (ENS)

Oceans and seas are becoming noisier with more vessels, increased seismic surveys for oil and gas, off-shore construction and recreation, and a new generation of military sonars, an alliance of wildlife groups said today. They warn that the cacophony is intensifying threats to marine mammals that use sound to communicate, forage for food and find mates.

The groups, attending the United Nations Environment Programme's Convention on Migratory Species conference in Rome, are urging governments and industry to adopt quieter engines for ships, tighter rules on the use of seismic surveys, and new, less intrusive sonar technologies by navies.

At the conference, the International Fund for Animal Welfare issued a report, "Ocean Noise: Turn it Down," showing that the distance over which blue whales can communicate is down by 90 percent as a result of intensified noise levels.

Ship noise in the Pacific Ocean has doubled every decade over the past 40 years and the global shipping fleet is expected to double in size by 2025, after doubling between 1965 and 2003, the report calculates.

Airguns used in seismic surveys generate "colossal" sounds peaking at up to 259 decibels and can be repeated every 10 seconds for months. These sounds travelled more than 3,000 km from the source. There are 90 seismic survey ships in the world, the report states, and a quarter of them are in use on any given day.

In addition, there are an estimated 300 naval sonar systems worldwide able to generate pressure sound waves of more than 235 decibels. Pings this loud are over one billion times more intense than the 145 decibel upper limit deemed safe for humans.

Veronica Frank, an attorney with the wildlife group, said, "We are calling for wide-ranging action, including a requirement that builders and owners of all vessels, from super-tankers down, working with the competent international body, factor noise reduction measures into vessels' design and operation at the outset."

The news of noisier oceans is emerging alongside new concerns that rising levels of the greenhouse gas carbon dioxide may be aggravating underwater noise levels.

Researchers at the Monterey Bay Aquarium Research Institute in the United States published a study in October showing that rising ocean acidity can make the marine environment noisier.

Conservative projections by the Intergovernmental Panel on Climate Change suggest that by 2050 the chemistry of seawater could increase in acidity by 0.3 pH units.

In the October 1, 2008 issue of "Geophysical Research Letters," Monterey Bay's Keith Hester and his co-authors calculate that by 2050 this change in ocean acidity would allow sounds to travel up to 70 percent farther underwater.

The more acidic the seawater, the less low-frequency and mid-frequency sound it absorbs, said Hester and his team. The changing chemistry of seawater may mean that currently it is 10 percent less absorbent of low frequency sound than it was prior to the Industrial Revolution.

Unless greenhouse gases emissions are cut - the key issue this week in Poznan, Poland at the annual UN climate conference - the rising ocean acid level will increase the amount of background noise in the oceans and could affect the behavior of marine mammals, said Hester.

Mark Simmonds, science director of the Whale and Dolphin Conservation Society, who is attending the Convention on Migratory Species meeting in Rome, said, "Underwater, man-made noise, is already triggering a kind of acoustic fog and a cacophony of sound in many parts of the world seas and oceans."
There is now evidence linking loud underwater noises with some major strandings of marine mammals, especially deep diving beaked whales, Simmonds said.

When cetaceans are startled by loud noise, they exhibit unusual diving behavior and suffer something similar to a human diver getting the bends, he said.

全文及圖片詳見:http://www.ens-newswire.com/ens/dec2008/2008-12-03-03.asp

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