2010年6月12日土曜日

ツバル沈下せず、周辺拡大

ツバルは沈下しないようだ。
 「太平洋の島々は成長を続けており、海面が上昇しても沈むことはない」。
そう主張する研究論文が英科学誌「ニュー・サイエンティスト」に掲載され、
議論を呼んでいる。

論文「変形する島々が海面上昇を否定」によると
過去60年間に撮影された航空写真と高解像度の衛星写真を使い、太平洋諸島
の27島の陸地表面の変化を調査。

結果
・海面は60年前よりも12センチ上昇
・表面積が縮小しているのは4島のみ。23島は変化なし、または、面積拡大。
 ツバルでは9島のうち7島が3%以上拡大、ウチ1島は約30%拡大。

サイクロンが島々に上陸したときに、波が岩礁や浜辺から珊瑚礁を破壊した
後、島の表面に置いていくことで、島が拡大していく自然現象とのこと。

温暖化懐疑論者が少しずつメッキをはがしていく。
でも、多くの人間が住んでいる4島は、土地整備が悪かったために生活でき
ず、転居せざるを得ない。いまさらだが、島の生い立ちが、珊瑚礁や火山岩
等の違いで、将来に渡って生活できるか検討する必要があり、自らの将来を
決断する時期なのかもしれない。
土地の住民は、土地整備を行い、快適にした米政府に対して、損害賠償
や慰謝料を請求するのか。

DNI 諜報活動のゴッドファーザ就任


---温暖化:「海面上昇でもツバル沈まず」 英科学誌に論文---
毎日新聞 2010年6月9日 12時37分(最終更新 6月9日 13時04分)
http://mainichi.jp/select/world/asia/news/20100609k0000e030062000c.html

 【ジャカルタ佐藤賢二郎】「太平洋の島々は成長を続けており、海面が上昇しても沈むことはない」--。そう主張する研究論文が英科学誌「ニュー・サイエンティスト」に掲載され、議論を呼んでいる。
 ツバルやキリバス、ミクロネシア連邦など南太平洋の島々は温暖化による海面上昇の影響で、将来的には地図上から消える「沈む島」と呼ばれてきた。
 論文のタイトルは「変形する島々が海面上昇を否定」。過去60年間に撮影された航空写真と高解像度の衛星写真を使い、ツバルやキリバスなど太平洋諸島の27島の陸地表面の変化を調査した。
 その結果、海面は60年前よりも12センチ上昇しているにもかかわらず、表面積が縮小しているのは4島のみ。23島は同じか逆に面積が拡大していることが明らかになった。ツバルでは九つの島のうち7島が3%以上拡大し、うち1島は約30%大きくなったという。
 拡大は「浸食されたサンゴのかけらが風や波によって陸地に押し上げられ、積み重なった結果」であり、「サンゴは生きており、材料を継続的に供給している」と説明。1972年にハリケーンに襲われたツバルで、140ヘクタールにわたってサンゴのかけらが堆積(たいせき)し、島の面積が10%拡大した事例を紹介している。
 研究に参加したオークランド大学(ニュージーランド)のポール・ケンチ准教授は「島々が海面上昇に対する回復力を備えていることを示す」と指摘し、「さらなる上昇にも対応する」と予測。一方、海面上昇が農業など島民生活に影響を与えることは避けられないとして、「どのような地下水面や作物が温暖化に適応できるか調べる必要がある」としている。


---Coral islands bigger despite ocean's rise---
Friday, 4 June 2010
http://www.independent.co.uk/environment/climate-change/coral-islands-bigger-despite-oceans-rise-1991017.html

Some South Pacific coral atolls have held their own or even grown in size over the past 60 years despite rising sea levels says new research.

Scientists worry that many of the tiny low-lying islands in the South Pacific will vanish under rising seas. But two researchers who measured 27 islands where local sea levels have risen 4.8in - an average of 0.08in per year - over the past 60 years, found just four had diminished in size. This is because coral islands respond to changes in weather patterns and climate, with coral debris eroded from encircling reefs pushed up on to the islands' coasts by wind and waves. Professor Paul Kench of Auckland University's environment school, and Arthur Webb of the Fiji-based South Pacific Applied Geoscience Commission, used historical aerial photographs and satellite images to study changes in the islands' land area.

While four were smaller, the other 23 had stayed the same or grown, according to the research, published in Global and Planetary Change.


---Low-lying Pacific islands 'growing not sinking'---
By Nick Bryant BBC News, Sydney
Page last updated at 6:07 GMT, Thursday, 3 June 2010 7:07 UK
http://news.bbc.co.uk/2/hi/world/asia_pacific/10222679.stm

A new geological study has shown that many low-lying Pacific islands are growing, not sinking.

The islands of Tuvalu, Kiribati and the Federated States of Micronesia are among those which have grown, because of coral debris and sediment.

The study, featured in the magazine the New Scientist, predicts that the islands will still be there in 100 years' time.

However it is still unsure whether many of them will be inhabitable.
Prognosis 'incorrect'

In recent times, the inhabitants of many low-lying Pacific islands have come to fear their homelands being wiped off the map because of rising sea levels.

But this study of 27 islands over the last 60 years suggests that most have remained stable, while some have actually grown.

Using historical photographs and satellite imaging, the geologists found that 80% of the islands had either remained the same or got larger - in some cases, dramatically so.

They say it is due to the build-up of coral debris and sediment, and to land reclamation.

Associate Professor Paul Kench of Auckland University, who took part in the study, published in the journal Global and Planetary Change, says the islands are not in immediate danger of extinction.

"That rather gloomy prognosis for these nations is incorrect," he said.

"We have now got the evidence to suggest that the physical foundation of these countries will still be there in 100 years, so they perhaps do not need to flee their country."

But although these islands might not be submerged under the waves in the short-term, it does not mean they will be inhabitable in the long-term, and the scientists believe further rises in sea levels pose a significant danger to the livelihoods of people living in Tuvalu, Kiribati and the Federated States of Micronesia.

One scientist in Kiribati said that people should not be lulled into thinking that inundation and coastal erosion were not a major threat.


---Pacific islands adapt to climate change---
By David Brooks (AFP) - 20100603
http://www.google.com/hostednews/afp/article/ALeqM5jgTEgMkoC0oVpPZOLi-cpM2FiEyA

WELLINGTON - New research has cast doubt on warnings that rising sea levels caused by climate change are slowly inundating low-lying Pacific islands.

Scientists have studied 27 low-lying Pacific islands, comparing aerial photos from 60 years ago with modern satellite images, according to an article published Wednesday in The New Scientist.

Paul Kench of the University of Auckland in New Zealand and Arthur Webb at the South Pacific Applied Geoscience Commission in Fiji found only four of those 27 islands had declined in size despite an average rise in sea level of 12 centimetres (4.7 inches) during the 60-year period.

Half of the rest had remained the same size and the other half had increased in size.

Kench told AFP Thursday the study shows that islands respond in different ways to climate change and rising seas.

"One thing our results tell us there is no one model fits all kind of scenario," Kench said.

It was important to have a sensible debate over the impact of climate change, "rather than just saying the sea level's going up and the islands must all disappear".

The study says some islands are growing because waves, currents and winds are pushing coral debris from the surrounding reefs onto the shore.

Although this study only involved studying the land area, Kench said his previous research had shown cyclones and storms -- which are predicted to become more frequent with climate change -- also often played an important role in increasing the height of islands.

"I've been in Tuvalu and know when cyclones hit Tuvalu, the waves go right across the island and in doing so, they are ripping up coral from the reef and beach and depositing them on the island surface.

"So there's a natural mechanism of how these islands can rise vertically and in many cases can keep pace with sea level rise projected over the next century."

Low-lying Pacific island nations such as Kiribati and Tuvalu have said they are suffering increasing problems due to rising sea levels -- including crop destruction and water contamination.

They say their citizens face the prospect of having to resettle in other countries as their islands are slowly submerged.

The study by Kench and Webb found that seven islands in one of Tuvalu's nine atolls have grown in area by more than three percent on average since the 1950s, with one island expanding nearly 30 percent.

A lot more research needed to be done to see how low-lying Pacific atolls would be affected by climate change, Kench said.

"We've looked at 27 islands out of around 20,000, so it's a very small sample, but it's given us some clues and I think we've got to expand that sample."

He said more research could lead to better identifying which islands in a Pacific country would best adapt to rising sea levels and villages could possibly be relocated to those islands.

More work also needed to be done to see how water tables and crops adapted to climate change.

"An important question is -- if islands still exist, will they still be able to carry human communities?"

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