Half of World’s Sandy Beaches at Risk from Climate Change

全球一半的沙灘面臨氣候變化威脅

Scientists say that half of the world's sandy beaches could disappear by the end of the century if climate change continues unchecked.

       科學家說，如果氣候變遷到本世紀末還未能有效控制(unchecked)的話，全球一半的沙灘可能消失。

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Half of World’s Sandy Beaches at Risk from Climate Change
VOA News｜Europe
March 02, 2020 04:58 PM (source)

Half of World's Sandy Beaches at Risk from Climate Change

全球一半的沙灘面臨氣候變化威脅

March 02, 2020 04:58 PM

Associated Press

Scientists say that half of the world's sandy beaches could disappear by the end of the century if climate change continues unchecked.

Researchers at the European Union's Joint Research Center in Ispra, Italy, used satellite images to track the way beaches have changed over the past 30 years and simulated how global warming might affect them in the future.

"What we find is that by the end of the century around half of the beaches in the world will experience erosion that is more than 100 meters," said Michalis Vousdoukas. "It's likely that they will be lost." 

The study, published Monday in the journal Nature Climate Change, found that the extent to which beaches are at risk depends on how much average global temperatures increase by the year 2100. Greater temperature increases mean more sea level rise and more violent storms in some regions, causing more beaches to vanish beneath the waves.

"The projected shoreline changes will substantially impact the shape of the world's coastline," more than a third of which is sandy beach, the authors wrote.

Beaches are valuable for recreation, tourism and wildlife, while also providing a natural barrier that protects coastal communities from waves and storms.

Many coastal areas, including beaches, are already heavily affected by human activity such as seashore construction and inland dams, which reduce the amount of silt flowing into oceans that's crucial for beach recovery.

Some countries will be more affected than others, the researchers said. Gambia and Guinea-Bissau in West Africa could lose more than 60% of their beaches, while predictions for Iraq, Pakistan, the island of Jersey in the English Channel and the Pacific island of Palau are similarly dire.

Australia would be hardest-hit in terms of total beach coastline lost, with over 12,000 kilometers (7,500 miles) at risk. The United States, Canada, Mexico, China, Iran, Argentina and Chile would also lose thousands of kilometers (miles) of beach, according to the study.

Andres Payo, an expert on coastal hazards and resilience at the British Geological Survey, said that while the study's methods were sound, its claims should be treated with caution.

"There are many assumptions and generalizations that could change the outcome of the analysis both qualitatively and quantitatively," said Payo, who wasn't involved in the study.

However, Vousdoukas said the amount of beach loss estimated by his team was in fact "a bit conservative" and could be higher.

The group considered two different warming scenarios _ one in which average global temperatures rise by 2.4 degrees Celsius by the end of the century and another that predicts an increase twice as high. The Paris climate accord's most ambitious target, of capping warming at 1.5 C, wasn't considered because scientists consider it unlikely to be achieved, Vousdoukas said.

The study's authors calculated that up to 40% of shoreline retreat could be prevented by reducing the greenhouse gas emissions that are driving climate change, but said that large and growing populations living along the coast will also need to be protected through other measures.

Citing the example of the Netherlands, which has battled the sea for centuries and even reclaimed substantial areas of low-lying land, the authors said "past experience has shown that effective site-specific coastal planning can mitigate beach erosion, eventually resulting in a stable coastline." 
 

科學家說，如果氣候變遷到本世紀末還未能有效控制(unchecked)的話，全球一半的沙灘可能消失。

位於義大利（Italy）伊斯普拉（Ispra）的歐盟聯合研究中心（European Union's Joint Research Center）的研究人員運用衛星(satellite)影像追蹤(track)了過去 30 年海灘的變化，並且模擬(simulate)了全球暖化(global warming)對未來海灘的影響。

「我們發現到本世紀末，世界上約有一半的海灘將遭受侵蝕(erosion)，且侵蝕程度高達 100 公尺以上。」研究員米卡利斯．伏斯杜卡斯（Michalis Vousdoukas）說：「這些海灘很可能會消失。」

這項研究於週一（編按：2020 年 3 月 2 日）發表在《自然氣候變化》（Nature Climate Change）期刊上。研究結果發現，海灘受到威脅的程度取決於到 2100 年全球平均氣溫升高多少。氣溫升高越多，代表著某些地區的海平面上升越多且面臨的暴風雨越強烈，因而導致更多的海灘在海浪的吞噬下消失(vanish，註 1)。

研究人員指出：「目前預測的(projected)海岸線變化將大幅度地(substantially，註 2)影響世界海岸線的形狀。」受到影響的海岸線中三分之一以上是沙灘。

海灘對於休閒娛樂、觀光旅遊以及野生動植物來說很重要，同時也提供了天然屏障(natural barrier)，可以避免沿岸社區受到海浪和暴風雨的影響。

許多包括海灘在內的海岸地區已經受到人類活動的嚴重影響，例如海濱建設和內陸水壩等建築減少了流入海洋的泥沙(silt，註 3)量，然而這些泥沙對於恢復原有的海灘至關重要。

研究人員說，相較於其他國家，某些國家會受到更大的影響。西非（West Africa）的岡比亞（Gambia）和幾內亞比紹（Guinea-Bissau）可能會失去超過60% 的海灘，而對於伊拉克（Iraq）、巴基斯坦（Pakistan）、英吉利海峽（English Channel）的澤西島（Jersey），以及帛琉（Palau）的太平洋島（Pacific Island）等地的海岸線變化，其預測的結果也同樣嚴重(dire，註 4)。

就海灘海岸線的消失而言，澳洲（Australia）可能會遭受最嚴重的打擊，該國超過 1 萬 2000 公里（7500 英里）的海岸受到威脅。這項研究顯示，美國（the United States）、加拿大（Canada）、墨西哥（Mexico）、中國（China）、伊朗（Iran）、阿根廷（Argentina）以及智利（Chile）也將失去數千公里的海灘。

安德烈斯．帕約（Andres Payo）是英國地質調查局（British Geological Survey）沿海災害（coastal hazards）與應變(resilience，註 5)專家。他表示，儘管這項研究使用的方法合理，但對其主張應謹慎(caution)看待。

未參與這項研究的帕約解釋：「有許多假設(assumption)和概括(generalization，註 6)都可能在質性和量化上改變分析的結果。」

不過，伏斯杜卡斯說，他團隊估計的海灘損失數量其實「有點保守(conservative，註 7)」，實際數量可能更高。

該小組考慮了兩種不同的暖化情景(scenario)：一種是到本世紀末全球平均氣溫升高攝氏 2.4 度，另一種則是預測氣溫升高為前者的兩倍。伏斯杜卡斯說，巴黎（Paris）氣候協議(accord，註 8)最雄心勃勃的目標是把升溫限制(cap)在攝氏 1.5 度以內，但因為科學家們認為這不可能實現，所以並未納入考量。

研究人員計算出，透過減少溫室氣體排放(emission)，可以防止多達 40% 的海岸線後退(retreat，註 9)，這些溫室氣體也是導致氣候變化的原因。然而他也提到，仍需要藉由其他措施來保護沿海地區大量且持續成長的人口。

研究人員以荷蘭（Netherlands）為例：該國與海洋奮戰(battle)了數百年，甚至開墾(reclaim)了許多低窪的(low-lying)土地，同時進一步解釋：「過去的經驗證明，針對特定地點制定的海岸規畫可以有效減緩(mitigate，註 10)海灘侵蝕，進而維持海岸線的穩定。」