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

1. 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 gotten 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. 2. 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 modeling approach. 3. 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. 4. 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. 5. 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. 6. Divergence between predicted suitability and actual distributions from the recent past indicates that unaccounted factors limit seagrass development in the southern Wadden Sea. 7. 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.

1. 20世纪70年代，富营养化（eutrophication）引发潮间带海草床（intertidal seagrasses）大规模衰退后，瓦登海（Wadden Sea）的海草群落呈现出分化的发展态势。瓦登海北部的海草床面积扩张且株密度提升，而南部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，瓦登海北部的海草恢复为构建可靠的生境适宜性模型（habitat suitability models）以辅助管理提供了契机。2. 本研究基于瓦登海北部17年的海草调查数据，结合全瓦登海的高分辨率水动力学（hydrodynamics）与地貌学（geomorphology）数据，采用5种机器学习方法对海草生境分布模型进行调优。为获得具有地理可迁移性的模型，研究通过非随机空间交叉验证（spatial cross-validation）评估预测精度，以此优化超参数（hyperparameters）。本研究将空间交叉验证方法与集成建模（consensus modeling）方法相结合。3. 预测得到的适宜性得分彼此之间存在相关性，且与训练区内的预留观测样本（hold-out observations）呈相关关系，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平均，进一步提升了预测精度。4. 本研究以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（Boyce index））为指标，可视化分析了集成模型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，证明了本预测方法的有效性。5. 本研究通过连续型博伊斯指数与生境适宜性得分的散点图，为整个跨国界的瓦登海划定了三类生境等级：不适宜生境、边缘适宜生境与适宜生境。该结果可为海草生境的保护与修复管理提供重要参考。6. 模型预测的适宜性与近期实际分布之间的差异表明，仍有未被纳入考量的因素限制了瓦登海南部海草的生长。7. 综合与应用：本研究的方法与数据支持我们构建了可靠且经过验证的集成生境适宜性模型。本研究划定了潮间带海草床可定植并持续存活的高适宜区域。本研究为动态滨海景观的高效保护规划提供了科学依据，并明确了监测优先级。