Vulnerability of Louisiana’s coastal wetlands to present-day rates of relative sea-level rise

Coastal Louisiana has lost about 5,000km2 of wetlands over the past century and concern exists whether remaining wetlands will persist while facing some of the world’s highest rates of relative sea-level rise (RSLR). Here we analyse an unprecedented data set derived from 274 rod surface-elevation table-marker horizon stations, to determine present-day surface-elevation change, vertical accretion and shallow subsidence rates. Comparison of vertical accretion rates with RSLR rates at the land surface (present-day RSLR rates are 12±8mm per year) shows that 65% of wetlands in the Mississippi Delta (SE Louisiana) may keep pace with RSLR, whereas 58% of the sites in the Chenier Plain (SW Louisiana) do not, rendering much of this area highly vulnerable to RLSR. At least 60% of the total subsidence rate occurs within the uppermost 5–10m, which may account for the higher vulnerability of coastal Louisiana wetlands compared to their counterparts elsewhere.

在过去的百年间，路易斯安那州沿海地区约丧失了5,000平方公里的湿地，对于剩余湿地在面临全球相对海平面上升（RSLR）速度最快的区域是否能够持续存在，存在一定的担忧。本研究分析了由274个地表标高表格标记的地面高程站点构成的创纪录数据集，以确定当前的地面高程变化、垂直沉积和浅层沉降速率。将垂直沉积速率与地表的RSLR速率进行比较（当前RSLR速率为每年12±8毫米），结果显示，密西西比三角洲（东南路易斯安那州）65%的湿地可能与RSLR保持同步，而陈纳平原（西南路易斯安那州）58%的站点则无法同步，使得该区域的大部分地区对RSLR极为脆弱。总沉降率至少有60%发生在最上层的5-10米范围内，这可能是路易斯安那州沿海湿地相对于其他地区湿地具有更高脆弱性的原因所在。