What is a significant threat to river ecosystems as noted in environmental science?

Pollution from sewage and garbage poses a significant threat to river ecosystems as it directly impacts water quality and the health of aquatic life. When sewage is released into rivers, it introduces pathogens, nutrients, and harmful chemicals that can lead to algal blooms, decreased oxygen levels, and the death of fish and other organisms. Garbage, including plastics and industrial waste, can physically harm wildlife, degrade habitats, and contribute to long-term ecological damage. This pollution disrupts the delicate balance of the river ecosystem, making it harder for species to thrive and often resulting in a loss of biodiversity.

While invasive species, climate change effects, and the construction of dams also present serious challenges to river ecosystems, the immediate and direct consequences of pollution from human activities make it one of the most pressing issues faced by these environments. Invasive species can alter food webs and compete with native species, climate change can affect water temperature and flow patterns, and dams can disrupt migration and sediment flow, but the impact of pollution is often more acute and visible.