Abstract Habitat degradation, entwined with land cover change, is a major driver of biodiversity loss. Effects of land cover change on species can be direct (when habitat is converted to alternative land cover types) or indirect (when land outside of the species habitat is altered). Hydrologic and ecological connections between terrestrial and aquatic systems are well understood, exemplifying how spatially disparate land cover conditions may influence aquatic habitats, but are rarely examined. We sought to quantify relative effects of land cover at two different but interacting scales on habitat suitability for the endangered arroyo toad (Anaxyrus californicus). Based on an existing distribution model for the arroyo toad and available land cover data, we estimated effects of land cover along streams and within entire watersheds on habitat suitability using structural equation modeling. Relationships between land cover and habitat suitability differed between scales, and broader, watershed-scale conditions influenced land cover along the embedded stream networks. We found anthropogenic development and forest cover at the watershed-scale negatively impacted habitat suitability, but development along stream networks was positively associated with suitability. The positive association between development along streams and habitat suitability may be attributable to increased spatial heterogeneity along urbanized streams, or related factors including policies designed to conserve riparian habitats amidst development. These findings show arroyo toad habitat is influenced by land cover across multiple scales, and can inform conservation of the species. Furthermore, our methodology can help elucidate similar dynamics with other taxa, particularly those reliant on both terrestrial and aquatic environments.

中文翻译：

---

土地覆盖和城市化对濒危蟾蜍栖息地适宜性的多尺度影响

摘要 栖息地退化与土地覆盖变化交织在一起，是生物多样性丧失的主要驱动因素。土地覆盖变化对物种的影响可以是直接的（当栖息地转变为替代的土地覆盖类型时）或间接的（当物种栖息地之外的土地被改变时）。陆地和水生系统之间的水文和生态联系是众所周知的，这说明了空间不同的土地覆盖条件如何影响水生栖息地，但很少被研究。我们试图量化土地覆盖在两个不同但相互作用的尺度上对濒危阿罗约蟾蜍（Anaxyrus californicus）栖息地适宜性的相对影响。基于现有的阿罗约蟾蜍分布模型和可用的土地覆盖数据，我们使用结构方程模型估计了河流沿岸和整个流域内的土地覆盖对栖息地适宜性的影响。土地覆盖和栖息地适宜性之间的关系因尺度而异，更广泛的流域尺度条件影响了嵌入河流网络沿线的土地覆盖。我们发现流域尺度的人为开发和森林覆盖对栖息地适宜性产生负面影响，但沿河流网络的开发与适宜性呈正相关。沿河流开发与栖息地适宜性之间的正相关可能归因于城市化河流沿线空间异质性的增加，或相关因素，包括旨在保护开发过程中河岸栖息地的政策。这些发现表明，阿罗约蟾蜍栖息地受到多尺度土地覆盖的影响，可以为该物种的保护提供信息。此外，我们的方法可以帮助阐明与其他类群的类似动态，特别是那些依赖陆地和水生环境的类群。