Threat to seagrass

Title: Threat to seagrass Description: This indicator shows whether mapped seagrass habitats are within 20 km of the river mouth of a river modelled to emit more than 1 tonne of plastic/year into the ocean. It is based on modelled plastic emissions at river mouths by Lebreton et al. (2017) overlaid with polygon of habitat extents. The calculated plastic emissions are based on upstream activities, where plastic is transported along the rivers to the river mouth. The amount of plastic at the river mouth as well as the distance from the habitat to the river mouth are used to define this indicator. This indicator compares the location of seagrass habitats with modelled plastic emissions from rivers. The plastic emissions are based on Lebreton et al. (2017), which models plastic that is discharged at river mouths, considering plastic with sizes between 0.3 and 500 mm. This study uses annual averages from the 6th version of the point estimates. These points are overlaid with a polygon of habitat extents from UNEP-WCMC Ocean Data Viewer was used to define the habitats. It was dissolved into a 5 by 5 km grid and the habitat area in each cell was calculated. Using these two inputs, the study investigated which habitats were within 20 km of a river that was modelled to emit 1 tonne of plastic/year or more. These two numbers were arbitrarily selected as there are no defined thresholds for when habitats are affected by plastic pollution. The study finds that 24.1% of seagrass habitats are within 20 km of a river modelled to emit more than 1 tonne of plastic/year. The majority of exposed seagrass habitats are on rocky coasts, and the exposed saltmarsh habitats are concentrated in southeast Asia, west Africa, and the Caribbean Sea. This indicator shows the seagrass habitats that are included in this study and whether they are within 20 km of a river modelled to emit more than 1 tonne of plastic/year. This layer is intended for informational, educational and research purposes only. More information about the data layer is available at: https://www.grida.no/publications/537 Source: GRID-Arendal Time Period: 1954-2018 (data range for UNEP-WCMC reefs data on which this data layer is based). Original Source: https://www.grida.no/publications/537 Partners: GRID-Arendal; University of Bergen; UNEP WCMC; The Modelling House标题：海草生境威胁 描述：本指标用于评估已绘制成图的海草生境是否位于某条模拟年向海洋排放塑料超过1吨的河流的20公里范围以内。该指标基于Lebreton等人（2017）的河口塑料排放模拟数据，并与生境范围多边形图层进行叠加分析。所计算的塑料排放量以流域上游活动为基础，塑料经河流输送至河口。河口塑料排放量以及生境至河口的距离共同用于界定本指标。本指标将海草生境的分布位置与河流模拟塑料排放量进行比对。该塑料排放数据源自Lebreton等人（2017）的研究，该研究针对0.3~500毫米粒径的塑料，模拟其在河口的排放情况。本研究采用第6版点估计值的年平均值。上述点数据与通过联合国环境规划署世界保护监测中心（UNEP-WCMC）海洋数据查看器获取的生境范围多边形图层进行叠加。将其聚合为5×5公里的网格单元，并计算每个单元内的生境面积。基于上述两项输入数据，本研究排查出位于年塑料排放量≥1吨的河流20公里范围以内的海草生境。由于尚无明确的海草生境受塑料污染影响的阈值标准，上述两项参数均为任意选定。研究结果显示，24.1%的海草生境位于年塑料排放量超过1吨的河流20公里范围以内。受影响的海草生境多分布于岩质海岸，而受影响的盐沼生境则集中分布于东南亚、西非及加勒比海海域。本指标涵盖本研究涉及的全部海草生境，并标注其是否位于年塑料排放量超过1吨的河流20公里范围以内。本数据图层仅用于信息展示、科普教育及科学研究。有关该数据图层的更多信息可访问：https://www.grida.no/publications/537 数据来源：GRID-Arendal（阿伦达尔环境信息中心） 时间范围：1954-2018年（本数据图层所依托的UNEP-WCMC珊瑚礁数据的时间范围） 原始来源：https://www.grida.no/publications/537 合作机构：GRID-Arendal（阿伦达尔环境信息中心）、卑尔根大学（University of Bergen）、联合国环境规划署世界保护监测中心（UNEP-WCMC）、建模事务所（The Modelling House）