Which statement best describes the environmental trade-off of hydropower compared to fossil fuels?

• A. Hydropower is clean in operation but can disrupt ecosystems due to dam construction.
• B. Hydropower emits more CO2 than coal plants.
• C. Hydropower requires rare earth mining for operation.
• D. Hydropower always destroys river ecosystems with no benefits.

Answer: (A)

Hydropower has very low greenhouse gas emissions during operation, which makes it clean compared with fossil fuels. The trade-off is that building dams and creating reservoirs can significantly disrupt river ecosystems—altering flow, blocking fish migration, changing sediment transport, and affecting habitats. This combination of low operable emissions with potential ecological disruption is why the statement is best. The other options misstate the emissions comparison, the reliance on rare earths, or the inevitability of complete ecosystem destruction.