Climate change projected to modify structural hillslope connectivity at the global scale

Structural connectivity describes how landscapes facilitate the transfer of matter and plays a critical role in the flux of water, solutes, and sediment across the Earth’s surface. The strength of a landscape’s connectivity is a function of climatic and tectonic processes, but the importance of these drivers is poorly understood, particularly in the context of climate change. Here, we provide global estimates of structural connectivity at the hillslope level and develop a model to describe connectivity accounting for tectonic and climate processes. We find that connectivity is primarily controlled by tectonics with climate as a second order control. However, we show climate change is projected to alter global-scale connectivity at the end of the century (2070 to 2100) by up to 4% for increasing greenhouse gas emission scenarios. Notably, the Ganges River, the world’s most populated basin, is projected to experience a large increase in connectivity. Conversely, the Amazon River and the Pacific coast of Patagonia are projected to experience the largest decreases in connectivity. Modeling suggests that as the climate warms, it could lead to increased erosion in source areas, while decreased rainfall may hinder sediment flow downstream, affecting landscape connectivity that poses implications for human and environmental health.

结构连通性（structural connectivity）描述了景观如何促进物质迁移，并在全球地表的水、溶质与沉积物输运过程中发挥关键作用。景观连通性的强弱取决于气候与构造过程，但学界对这些驱动因子的重要性认知仍较为匮乏，在气候变化背景下这一问题尤为突出。本研究提供了坡面尺度下的全球结构连通性估算结果，并构建了兼顾构造与气候过程的连通性描述模型。研究发现，连通性主要受构造作用调控，气候仅为次级调控因子。不过，本研究显示，在温室气体排放加剧的情景下，预计到本世纪末（2070至2100年），全球尺度的连通性将出现最高达4%的变化。值得注意的是，作为全球人口最密集的流域，恒河流域的连通性预计将出现大幅提升；与之相反，亚马孙河流域与巴塔哥尼亚太平洋沿岸的连通性则预计出现最大幅度的下降。模型模拟结果表明，气候变暖将导致物源区侵蚀加剧，而降雨减少则会阻碍沉积物向下游输运，进而影响景观连通性，这一变化将对人类健康与生态环境健康产生重要影响。