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 is 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 in 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.