世界規模でのデルタ形状への影響は,土地の純増量をもたらしました
J H Nienhuis1,2,3,4, A D Ashton5, D A Edmonds6
1Department of Physical Geography, Utrecht University, Utrecht, The Netherlands. j.h.nienhuis@uu.nl.
Nature
|January 24, 2020
まとめ
地球上のデルタは 森林破壊などの人間の活動によって 土地が増えているが 川のが多くのデルタで 重要な土地の損失を引き起こしている 将来の海面上昇はこれらの成果を脅かし,沈殿物の動態を理解する必要性を強調しています.
科学分野:
- 地球と環境科学
- 地形学
- 沿岸科学
背景:
- 川のデルタは 経済的にも生態学的にも 重要なシステムです
- デルタは,沈殿物の供給の減少と気候変動によって,沿岸の危険が増加しています.
- 堆積物,海洋力,デルタ形状の相互作用はよく理解されていません.
研究 の 目的:
- 川の堤防と森林伐採が世界のデルタ形状に与える影響を定量化する.
- 波,潮,川の支配の影響によるデルタ形状の連続性をモデル化すること.
- デルタの近年の土地面の変化と特質の要因を評価する.
主な方法:
- 世界中で約11,000の沿岸デルタの形状分析
- 波,潮,川の影響に基づいてデルタ形状を分類するモデルの開発.
- 過去30年の土地面積の変化を定量化し,人間の活動による影響
主要な成果:
- デルタの形状は波 (80%) 潮 (10%) 川 (10%) が支配する連続体で変化します.
- 世界的に見ると,デルタは30年間で54 ± 12 km2/年増加し,その25%は森林破壊に起因しています.
- 河川の堤防により,約1,000のデルタで堆積物流が50%以上減少し,年間12 ± 3.5 km2の集団的な土地損失をもたらしました.
結論:
- 人間の活動がデルタの土地面の変化に大きく影響し,森林伐採が利益をもたらし,ダム建設が損失をもたらしています.
- 現在,いくつかのデルタは支配権の移行により土地を獲得していますが,海面上昇の加速は将来の土地の安定を脅かしています.
- 潮による沈殿物の再分布を理解することは 人為的なデルタの変化を予測するのに不可欠です
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