Data from: Forty years of seagrass population stability and resilience in an urbanizing estuary

Coasts and estuaries contain among the most productive and ecologically important habitats in the world and face intense pressure from current and projected human activities, including coastal development. Seagrasses are a key habitat feature in many estuaries perceived to be in widespread decline owing to human actions.
We use spatio-temporal models and a 41-year time-series from 100s of km of shoreline which includes over 160,000 observations from Puget Sound, Washington, USA to examine multi-scale trends and drivers of eelgrass (Zostera spp.) change in an urbanizing estuary.
At whole estuary scale (100s of km) we find a stable and resilient eelgrass population despite a more than doubling of human population density and multiple major climactic stressors (e.g. ENSO events) over the period. However, the aggregate trend is not reflected at the site scale (10s of km), where some sites persistently increase while others decline.
Site trends were spatially asynchronous; adjacent sites sometimes exhibited opposite trends over the same period. Substantial change in eelgrass occurred at the sub-site (0.1 km) scale, including both complete local loss and dramatic increase of eelgrass.
Metrics of local human development including shoreline armoring, upland development (imperviousness), and human density provide no explanatory power for eelgrass population change at any spatial scale.
Our results suggest that the appropriate scale for understanding eelgrass change is smaller than typically assumed (approximately 1 to 3 km scale) and contrasts strongly with previous work.
Synthesis. Despite ongoing conservation concern over seagrasses worldwide, eelgrass in Puget Sound has been highly resilient to both anthropogenic and environmental change over four decades. Our work provides general methods that can be applied to understand spatial and temporal scales of change and can be used to assess hypothesized drivers of change.

海岸与河口是全球生产力最高、生态价值最为重要的生境类型之一，同时正面临当前及未来人类活动（包括海岸开发）的强烈干扰压力。海草是众多河口的关键生境特征，且因人类活动而被认为正处于大范围衰退之中。
本研究采用时空模型（spatio-temporal models），结合源自美国华盛顿州普吉特湾（Puget Sound）数百公里岸线、包含超16万条观测记录的41年时间序列数据，探究城市化河口内鳗草（Zostera spp.）种群变化的多尺度趋势与驱动因子。
在整个河口尺度（数百公里级别）下，尽管研究期间人类人口密度增长超一倍，且遭遇了多次重大气候胁迫事件（如厄尔尼诺-南方涛动(ENSO)事件），鳗草种群仍保持稳定且具备较强恢复力。然而，这一整体趋势在区域站点尺度（数十公里级别）下并未体现：部分站点的鳗草种群持续增长，而另一些则出现衰退。
各站点的种群变化趋势在空间上呈现异步性；相邻站点在同期有时会表现出完全相反的变化趋势。鳗草种群的显著变化则发生在亚站点尺度（0.1公里级别），既包括局部种群的完全消失，也包括鳗草覆盖范围的大幅扩张。
当地人类开发活动相关指标，包括岸线加固、高地开发（不透水面，imperviousness）以及人口密度，均无法解释任何空间尺度下的鳗草种群变化。
本研究结果表明，解析鳗草种群变化的适宜空间尺度小于此前的普遍认知（约1至3公里级别），这与既往研究结论存在显著差异。
研究综合：尽管全球范围内海草仍持续受到保护层面的关注，但普吉特湾的鳗草种群在过去四十年间，对人为活动与环境变化均展现出极强的恢复力。本研究提出的通用方法可用于解析变化的时空尺度，也可用于评估已被提出的种群变化驱动因子。