Coastal tidal wetland change in the northeastern United States

Coastal tidal wetlands are highly altered ecosystems at substantial risk due to widespread and frequent land-use change, coupled with sea-level rise, leading to disrupted hydrologic and ecologic functions and ultimately, significant reduction in climate resiliency. Knowing where and when the changes have occurred, and the nature of those changes and their associated risks, is paramount to coastal communities and natural resource management. Large-scale mapping of the costal tidal wetland changes is extremely difficult due to their inherent dynamic nature.
To bridge this gap, we developed an automated algorithm for DEtection and Characterization of cOastal tiDal wEtlands change (DECODE) using dense Landsat time series. We used DECODE to track the status of coastal tidal wetlands in the northeastern United States from 1986 to 2020. The overall accuracy of land cover classification and change detection is approximate 95.8% and 99.8%, respectively. The vegetated wetlands and open water were mapped with 94.6% and 99.0% user’s accuracy, and 98.1% and 93.5% producer’s accuracy, respectively. The cover change and condition change were mapped with 68.0% and 80.0% user’s accuracy, and 80.5% and 97.1% producer’s accuracy, respectively. We discovered that approximately 3283 km2 (12%) of coastal tidal wetlands in the northeastern United States occurred at least one time of change but condition changes were responsible for majority (84.3%). Vegetated coastal tidal wetland decreased consistently (approximately 2.6 km2 per year) in the past 35 years, largely due to its conversion to open water.

海岸潮汐湿地是经过高度改造的生态系统，其面临着因广泛且频繁的土地利用变化以及海平面上升而带来的巨大风险。这些变化干扰了水文和生态功能，最终导致气候适应能力的显著下降。了解变化的地点、时间以及变化的性质及其相关风险，对于沿海社区和自然资源管理至关重要。由于海岸潮汐湿地的内在动态特性，对其变化的规模化制图极为困难。为了弥合这一差距，我们开发了一种名为DECODE（海岸潮汐湿地变化检测与表征自动化算法）的算法，利用密集的Landsat时间序列数据。我们运用DECODE对1986年至2020年美国东北部海岸潮汐湿地的状况进行了追踪。土地覆盖分类和变化检测的整体精度分别约为95.8%和99.8%。植被湿地和开阔水域的制图用户精度分别达到94.6%和99.0%，而制图者精度分别达到98.1%和93.5%。覆盖变化和状况变化的制图用户精度分别为68.0%和80.0%，制图者精度分别为80.5%和97.1%。我们发现，美国东北部约3283平方公里（12%）的海岸潮汐湿地至少经历了一次变化，其中状况变化占主导地位（84.3%）。在过去35年间，植被海岸潮汐湿地持续减少（每年约减少2.6平方公里），这主要归因于其转化为开阔水域。