Why are people concerned that hydropower will harm an ecosystem

Dams can also harm the water ecosystems in which they operate. Turbines and other equipment sometimes kill fish and other creatures, and changing the animals' habitat can also be damaging. Installing hydropower can also alter the quality of the water it's located in.

it would affect precipitation by causing flooding in some areas of the world due to climate increasing, causing the glaciers in the northern and southern pole of our planet to melt.

i wish you would have provided choices to simplify it and allow me to give an exact answer.