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河川管理が世界有数の湿地保全の主要因であることを解明(Researchers reveal why river management is so crucial to protecting one of world’s most important wetlands)

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2026-07-27 スウォンジー大学

スウォンジー大学の研究チームは、イラク南部の世界遺産「メソポタミア湿地」の保全には、現地の降雨量よりもチグリス川・ユーフラテス川の上流域における河川管理が決定的に重要であることを明らかにした。研究では、2000~2023年のNASA MODIS、Copernicus Sentinel-2、JRC Global Surface Waterなどの衛星データに加え、河川流量や降水量データを解析した。その結果、2003年以降の湿地回復は進んだものの、2008~2009年および2022~2023年には干ばつや上流ダムの運用、水資源管理の影響で植生と水域が大幅に減少したことが判明した。また、植生量は河川流量と強く相関する一方、地域降雨との関連は認められなかった。さらに、植生が豊富な地域では地表面温度が低く、植生減少が気温上昇を招く正のフィードバックも確認された。研究は、湿地保全には国境を越えた流域管理と国際協力が不可欠であることを示している。

河川管理が世界有数の湿地保全の主要因であることを解明(Researchers reveal why river management is so crucial to protecting one of world’s most important wetlands)
A boat stranded on dried-out marshland in the Mesopotamian Marshes, southern Iraq, due to drought.

<関連情報>

2000年から2023年の期間における気候要因と地表水管理がメソポタミア湿地に与える影響 The impact of climate factors and surface water management on the Mesopotamian Marshes for the period 2000–2023

Akram Alqaraghuli,Peter North,Sietse Los,Iain Bye & Jacqueline Rosette
Scientific Reports  Published:15 July 2026
DOI:https://doi.org/10.1038/s41598-026-61808-9  Unedited version

Abstract

The Mesopotamian Marshes, a UNESCO World Heritage site in southern Iraq, have experienced severe degradation due to climate change, upstream dam construction, and water management policies. This study quantifies the drivers of vegetation and water dynamics from 2000 to 2023 — a period spanning post-2003 restoration, the full MODIS record, and recent droughts. We integrated MODIS, Sentinel-2, JRC Global Surface Water, CHIRPS precipitation, and streamflow data, applying spectral indices (NDVI, MNDWI), regression, cross-correlation, hysteresis, partial correlation, and Mann-Kendall tests with Sen’s slope. Vegetation area ranged from 550 to 2,600 km², and water area from 100 to 1,650 km². Mann-Kendall analysis revealed that water area increased significantly (τ = 0.41, p < 0.01) with a Sen’s slope of 16.43 km² yr⁻¹, while vegetation showed a trend with a Sen’s slope of 36.60 km² yr⁻¹ (τ = 0.30, p = 0.05). Land Surface Temperature (LST) showed the strongest negative correlation with vegetation (R = − 0.87). Streamflow was the dominant predictor of vegetation area (p = 0.029, R = 0.81), while local precipitation had no significant effect. Cross-correlation showed that vegetation decline precedes temperature increases (R = − 0.74 at lag 1 year), confirming a positive feedback loop. Partial correlation confirmed vegetation’s independent cooling effect (P = − 0.82) beyond open water. Major water and vegetation losses occurred in 2008–2009 and 2022–2023, linked to upstream drought, dam operations, and water policies. We conclude that transboundary water management, not local rainfall, governs marshland sustainability. These findings provide quantitative evidence for policymakers to prioritize river flow allocation over local precipitation in arid-region wetland conservation.

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