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荷兰乌得勒支大学J. H. Nienhuis等研究人员发现，全球范围内人类对三角洲形态的影响导致净土地面积增加。该项研究成果于2020年1月22日在线发表于《自然》杂志。

研究人员展示了全球约11000个沿海三角洲的形态（从小湾角三角洲到巨型三角洲）如何受到河坝和森林砍伐的影响。研究人员引入了一个模型，其表明当今的三角洲形态在波浪（约占80％）、潮汐（约占10％）和河流（约占10％）的主导地位之间连续变化，但是大多数三角洲都是潮汐和河流为主。

在过去30年中，尽管海平面上升，但全球三角洲每年仍净增土地净额54±12平方公里（标准差为2），其中最大的三角洲占总三角洲的30％土地净收益。人类是这些土地净增加的重要驱动力，即三角洲增长的25％，可以归因于森林砍伐引起的河流沉积物供应增加。然而，对于近1000个三角洲而言，大坝导致人为沉积物通量急剧下降（超过50％），迫使三角洲土地每年集体损失12±3.5平方公里（标准差为2）。

并非所有三角洲都会因河水泛滥而失去土地：向潮汐主导地位过渡的三角洲目前正在获得土地，可能是通过渠道充填。然而，由于预计海平面将加速上升，因此在整个二十一世纪，近期的土地增长不太可能持续。了解波浪和潮汐造成的沉积物重新分布对于成功预测人类引起的三角洲局部和全球变化至关重要。

据介绍，三角洲是地球上最具经济和生态价值的环境之一。即使没有海平面上升，三角洲也越来越容易受到沿海灾害的威胁，因为沉积物供应的减少和气候变化改变了沉积物的预期，从而影响了三角洲的形态，并可能导致水土流失。但是，三角洲沉积物预期、海浪和潮汐的海洋学力以及三角洲形态之间的关系仍然很难量化。

附：英文原文

Title: Global-scale human impact on delta morphology has led to net land area gain

Author: J. H. Nienhuis, A. D. Ashton, D. A. Edmonds, A. J. F. Hoitink, A. J. Kettner, J. C. Rowland, T. E. Trnqvist

Issue&Volume: 2020-01-22

Abstract: 

River deltas rank among the most economically and ecologically valuable environments on Earth. Even in the absence of sea-level rise, deltas are increasingly vulnerable to coastal hazards as declining sediment supply and climate change alter their sediment budget, affecting delta morphology and possibly leading to erosion1,2,3. However, the relationship between deltaic sediment budgets, oceanographic forces of waves and tides, and delta morphology has remained poorly quantified. Here we show how the morphology of about 11,000 coastal deltas worldwide, ranging from small bayhead deltas to mega-deltas, has been affected by river damming and deforestation. We introduce a model that shows that present-day delta morphology varies across a continuum between wave (about 80 per cent), tide (around 10 per cent) and river (about 10 per cent) dominance, but that most large deltas are tide- and river-dominated. Over the past 30 years, despite sea-level rise, deltas globally have experienced a net land gain of 54 ± 12 square kilometres per year (2 standard deviations), with the largest 1 per cent of deltas being responsible for 30 per cent of all net land area gains. Humans are a considerable driver of these net land gains—25 per cent of delta growth can be attributed to deforestation-induced increases in fluvial sediment supply. Yet for nearly 1,000 deltas, river damming4 has resulted in a severe (more than 50 per cent) reduction in anthropogenic sediment flux, forcing a collective loss of 12 ± 3.5 square kilometres per year (2 standard deviations) of deltaic land. Not all deltas lose land in response to river damming: deltas transitioning towards tide dominance are currently gaining land, probably through channel infilling. With expected accelerated sea-level rise5, however, recent land gains are unlikely to be sustained throughout the twenty-first century. Understanding the redistribution of sediments by waves and tides will be critical for successfully predicting human-driven change to deltas, both locally and globally.

DOI: 10.1038/s41586-019-1905-9

Source: https://www.nature.com/articles/s41586-019-1905-9

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