Hydrochory, a Key Ecological Function of a Tropical Dry Forest River Threatened by a Dam and Open‐Pit Coal Mining in Colombia.

Aims: Freshwater ecosystems have complex spatial and temporal connections that support multiple processes essential for life. Since two of the most critical impacts on riparian ecosystems are the regulation of river flows and water pollution, we aimed to investigate whether a dam and mining activities on the Ranchería River affect hydrochory. Location: Tropical dry forest of La Guajira, Colombia; a region in need of water. Methods: We evaluated hydrochory and compared seed richness, abundance, and composition with the unaltered Cesar River over two seasons. We sampled both upstream and downstream of the dam and the mining site. At these same sites, we quantified levels of turbidity and 15 chemical compounds that affect water quality. Results: There was significant spatial heterogeneity of the seed communities sampled along both rivers, with particularly distinct communities collected downstream from the open pit mine. We also found a significant effect of the dam on seed composition and abundance in the Ranchería River. Seed assemblages, but not seed numbers, differed between seasons and rivers. We also found significantly higher levels of chemical compounds and turbidity downstream of the mine compared to upstream. Conclusions: There is a significant effect of the dam and the open pit mine on the Ranchería River in Colombia. The alteration of natural flows, environmental conditions, and water quality affects hydrochory, a key ecological function of the river. Urgent measures are imperative to address these challenges effectively and ensure the long‐term sustainability of the ecosystem. [ABSTRACT FROM AUTHOR]