Coastal wetlands provide vital dynamic ecosystem services. They have become increasingly important after being linked to several sustainable developmental goals, resulting in a focus on their protection, management, and restoration. Therefore, there is an increasing need to detect and compare coastal wetland spatiotemporal dynamics in deltas at a global scale. In this study, we mapped and characterized coastal wetland spatiotemporal patterns for 1990–2019 in the world’s major river deltas using pixel frequency algorithms and Landsat-4/5 (TM), −7 (ETM + ), −8 (OLI), and Sentinel-2 (MSI) time-series imagery obtained from Google Earth Engine (GEE). Our map had a high overall accuracy (91.84 %) for 2019. Tidal flats were primarily distributed in North America (∼6.87 %) and Asia (∼5.91 %), whereas salt marshes were more commonly found in North America (∼45.39 %) and South America (∼10.61 %). Mangroves are more common in South America (∼11.86 %) and Asia (∼5.83 %), primarily because of the Amazon River Delta and tropical and subtropical regions of Asia, which host several large river deltas. South America had the largest coastal delta wetland area (798,569 km2), followed by Asia (640,251 km2), North America (581,977 km2), Africa (181,977 km2), Europe (140,759 km2), and Oceania (15,915 km2). There was a minor difference in the distribution of wetland vegetation and tidal flats in Asian coastal deltas, and the wetland vegetation area in Asia was greater than that in tidal flats on other continents. We found that the coastal wetland areas increased during 1990–2001, decreased during 2001–2012, and steadily increased during 2012–2019. Our study provides a baseline for monitoring the area, status, and health of the coastal wetlands in these river deltas.

中文翻译：

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1990—2019 年世界主要河流三角洲沿海湿地的不同动态


沿海湿地提供重要的动态生态系统服务。在与几个可持续发展目标相关联后，它们变得越来越重要，因此人们开始关注它们的保护、管理和恢复。因此，在全球范围内检测和比较三角洲沿海湿地时空动态的需求越来越大。在这项研究中，我们使用像素频率算法和从 Google Earth Engine （GEE） 获得的 Landsat-4/5 （TM）、-7 （ETM +）、-8 （OLI） 和 Sentinel-2 （MSI） 时间序列图像，绘制并表征了 1990-2019 年世界主要河流三角洲的沿海湿地时空模式。我们的地图在 2019 年的总体准确率很高 （91.84%）。滩涂主要分布在北美 （∼6.87 %） 和亚洲 （∼5.91 %），而盐沼更常见于北美 （∼45.39 %） 和南美洲 （∼10.61 %）。红树林在南美洲 （∼11.86 %） 和亚洲 （∼5.83 %） 更为常见，主要是因为亚马逊河三角洲以及亚洲的热带和亚热带地区拥有几个大型河流三角洲。南美洲的沿海三角洲湿地面积最大（798,569 km2），其次是亚洲（640,251 km2）、北美（581,977 km2）、非洲（181,977 km2）、欧洲（140,759 km2）和大洋洲（15,915 km2）。亚洲沿海三角洲湿地植被和滩涂分布差异较小，亚洲湿地植被面积大于其他大洲滩涂。研究发现，沿海湿地面积在 1990—2001 年期间增加，在 2001—2012 年期间减少，在 2012—2019 年期间稳步增加。我们的研究为监测这些河流三角洲沿海湿地的面积、状况和健康状况提供了基线。