海氷減少で「セイウチがうじゃうじゃ」【動画】

生息域である北極の海氷が減少し、行き場を失ってしまった結果として、およそ1万頭のタイヘイヨウセイウチが、アラスカの浜辺で大集団を形成している。その様子を撮影した画像がこのほど公開された。

生息域である北極の海氷が減少し、行き場を失ってしまった結果として、およそ1万頭のタイヘイヨウセイウチが、アラスカの浜辺で大集団を形成している。その様子を撮影した画像がこのほど公開された。

浜辺でぎゅうぎゅう詰めになるその痛ましい姿を撮影したのは、米国海洋大気庁(NOAA)の研究者たちだ。

セイウチたちは現在、アラスカ州アンカレッジの北西およそ1125キロメートルの地点にある小さな浜辺に、すし詰め状態となっている。研究者たちは、地球温暖化で生息域の氷が溶解してしまったからだと説明している。

セイウチはこれまで、氷塊の上で休憩し、そこから海底に潜って餌を獲って暮らしていた。しかしここ最近、海氷が大規模に消失しており、大陸棚の浅瀬からはるか離れた沖のほうにしか残っていない。

セイウチが浜辺に集結する現象は、温暖化で夏に北極の海氷が大規模に溶け出している現象(日本語版記事)に伴って起きている。

その混雑ぶりは凄まじく、一部のセイウチが暴走したら、幼い個体を中心に圧死が生じると危惧されている。ホッキョクグマや猟師、低空で飛ぶ飛行機などに驚けば、暴走の可能性があるのだ。

Open Image Modal

米国魚類野生生物局(FWS)は、セイウチを刺激しないよう対策に乗り出している。AP通信によると、FWSは近隣の住民と協力して、セイウチが暴走しないよう、人の立ち入りや航空機の飛行を制限しているという。

2009年には、チュクチ海に面するアラスカのアイシー岬でセイウチの暴走が発生し、130頭の死骸が確認された。そのほとんどは幼いセイウチだった。

氷の失われた北極圏では、ホッキョクグマの餓死も報道されている(日本語版記事)。

[(English) 日本語版:遠藤康子/ガリレオ]

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