1. Climate change is generating extreme climate events, affecting ecosystem integrity and function directly through increases in abiotic stress and disturbance and indirectly through changes in the strength of biotic interactions. As consumers play an essential role in ecosystem functioning and have been shown to be highly sensitive to climate conditions, improved understanding of their role under changing environmental conditions is necessary to accurately anticipate climate change impacts on ecosystem integrity.
2. We evaluated if prolonged periods of extreme rain, a climatic event increasing in severity in many places around the world, and coincident increases in coastal flooding duration intensify consumer control of foundational salt marsh grass structure and quantify the consequences of flooding–consumer interactions on salt marsh range extent. To achieve this, we analysed: historic trends in crab grazing; crab numbers and activity in and out of rainy years on the low marsh edge; vegetation retreat from the low marsh edge at a plot scale in a manipulative exclosure experiment; vegetation retreat at a landscape-scale from drone image analyses; and the vertical erosion in the lowest edge of an Argentinean salt marsh.
3. During flooded periods, crabs congregated in the low marsh, resulting in localized overgrazing of salt marsh grass and the rapid horizontal retreat of the marsh edge (98.5 cm on average). Salt marsh edge retreat resulted in a loss of ~4.5% of the total marsh area at the landscape scale. Inside crab exclusion plots, although grass cover declined slightly during the study period, the marsh edge did not retreat.
4. Synthesis. This study provides experimental evidence that an extreme climate event can destabilize a local consumer–prey interaction, indirectly triggering the range contraction of a critical coastal habitat. This work contributes to a growing body of research demonstrating that consumers can be unleashed, rather than suppressed, by extreme climatic events. Moreover, in cases where consumer fronts form during such events, the result can be not only local (along habitat edges) but also landscape-scale extinction of foundation species and the habitats they biogenically create. Together, this supports the general idea that models of future climate scenarios integrate the indirect effects on ecosystem-regulating food web interactions.

中文翻译：

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洪水刺激的食草动物驱动植物生态系统的范围收缩

1. 气候变化正在产生极端气候事件，通过增加非生物压力和干扰直接影响生态系统完整性和功能，并通过改变生物相互作用强度间接影响生态系统。由于消费者在生态系统功能中发挥着重要作用，并且已被证明对气候条件高度敏感，因此有必要更好地了解他们在不断变化的环境条件下的作用，以准确预测气候变化对生态系统完整性的影响。
2. 我们评估了长时间的极端降雨、全球许多地方严重性增加的气候事件以及沿海洪水持续时间的同时增加是否会加强消费者对基础盐沼草结构的控制，并量化洪水与消费者相互作用对盐沼的影响范围。为实现这一目标，我们分析了： 螃蟹放牧的历史趋势；在低沼泽边缘的雨季内外的螃蟹数量和活动；在操纵性封闭实验中，植被从低沼泽边缘以地块尺度撤退；从无人机图像分析得出的景观尺度上的植被后退；以及阿根廷盐沼最低边缘的垂直侵蚀。
3. 洪水期，螃蟹聚集在低洼沼泽，造成盐沼草局部过度放牧，沼泽边缘迅速水平后退（平均98.5厘米）。盐沼边缘退缩导致景观尺度上沼泽总面积减少约 4.5%。在螃蟹排除地块内，虽然在研究期间草覆盖率略有下降，但沼泽边缘并没有后退。
4. 合成。这项研究提供了实验证据，表明极端气候事件会破坏当地消费者与猎物之间的相互作用，间接引发关键沿海栖息地的范围缩小。这项工作有助于越来越多的研究表明，极端气候事件可以释放而不是抑制消费者。此外，在此类事件期间形成消费者阵线的情况下，结果不仅可能是局部（沿栖息地边缘），而且可能导致基础物种及其生物产生的栖息地在景观范围内灭绝。总之，这支持了未来气候情景模型整合了对生态系统调节食物网相互作用的间接影响的总体想法。