Data from: Consensus forecasting of intertidal seagrass habitat in the Wadden Sea

After the dramatic eutrophication-induced decline of intertidal seagrasses in the 1970s, the Wadden Sea has shown diverging developments. In the northern Wadden Sea, seagrass beds have expanded and become denser, while in the southern Wadden Sea, only small beds with low shoot densities are found. A lack of documentation of historical distributions hampers conservation management. Yet, the recovery in the northern Wadden Sea provides opportunity to construct robust habitat suitability models to support management. We tuned habitat distribution models based on 17 years of seagrass surveys in the northern Wadden Sea and high-resolution hydrodynamics and geomorphology for the entire Wadden Sea using five machine learning approaches. To obtain geographically transferable models, hyperparameters were tuned on the basis of prediction accuracy assessed by non-random, spatial cross-validation. The spatial cross-validation methodology was combined with a consensus modelling approach. The predicted suitability scores correlated amongst each other and with the hold-out observations in the training area indicating that the models converged and were transferable across space. Prediction accuracy was improved by averaging the predictions of the best models. We graphically examined the relationship between the consensus suitability score and independent presence-only data from outside the training area using the area-adjusted seagrass frequency per suitability class (continuous Boyce index). The Boyce index was positively correlated with the suitability score indicating the adequacy of the prediction methodology. We used the plot of the continuous Boyce index against habitat suitability score to demarcate three habitat classes – unsuitable, marginal and suitable – for the entire international Wadden Sea. This information is valuable for habitat conservation and restoration management. Divergence between predicted suitability and actual distributions from the recent past indicates that unaccounted factors limit seagrass development in the southern Wadden Sea. Synthesis and applications. Our methodology and data enabled us to produce a robust and validated consensus habitat suitability model. We identified highly suitable areas where intertidal seagrass meadows may establish and persist. Our work provides scientific underpinning for effective conservation planning in a dynamic landscape and sets monitoring priorities.20世纪70年代，受富营养化（eutrophication）影响，潮间带海草（intertidal seagrasses）出现大规模衰退，此后瓦登海（Wadden Sea）的海草群落呈现分化发展态势。北瓦登海的海草床不断扩张、密度持续升高，而南瓦登海仅存少量株密度较低的小型海草床。历史分布记录的缺失，阻碍了海草的保护管理工作。不过，北瓦登海的海草恢复为构建可靠的生境适宜性模型（habitat suitability models）以支撑管理工作提供了契机。 本研究基于北瓦登海17年的海草调查数据，结合全瓦登海的高分辨率水动力（hydrodynamics）与地貌（geomorphology）数据，采用5种机器学习方法（machine learning approaches）对生境分布模型进行了调优。为获得具有空间可迁移性的模型，本研究基于非随机空间交叉验证（spatial cross-validation）评估的预测精度对超参数（hyperparameters）进行了调优，并将该方法与集成建模方法（consensus modelling approach）相结合。 预测得到的适宜性得分彼此之间，以及与训练区的预留观测样本（hold-out observations）均呈现显著相关，表明模型收敛且具备空间可迁移性。通过对最优模型的预测结果取均值，进一步提升了预测精度。 本研究通过按适宜性等级调整面积后的海草出现频率（即连续型博伊斯指数（continuous Boyce index）），可视化分析了集成适宜性得分与训练区外独立仅存在数据（presence-only data）之间的关系。博伊斯指数与适宜性得分呈正相关，证明本研究的预测方法具备合理性。 本研究基于连续型博伊斯指数与生境适宜性得分的散点图，为整个国际瓦登海划定了三类生境等级：不适宜（unsuitable）、边缘适宜（marginal）与适宜（suitable）。该结果对于海草生境的保护与修复管理具有重要价值。 近期预测适宜性与实际分布之间的差异表明，尚有未被纳入考量的因素限制了南瓦登海的海草生长。 总结与应用：本研究的方法与数据支撑我们构建了可靠且经过验证的集成生境适宜性模型。本研究明确了潮间带海草床能够定植并持续生长的高适宜区域。本研究为动态海岸带的高效保护规划提供了科学依据，并确立了监测优先级。