Human activity can affect the river ecosystems because first of all humans take the water and use it for themselves, they also pollute it, disturb the ecosystems and kill fish or oysters etc. in the ecosystems.
Although river water makes up only about 0.2 percent of all the fresh water on Earth, it plays a very important role. Rivers are like roads. They carry water, organisms and important gases and nutrients to many areas. They also help drain rainwater and provide habitats for many species of plants and animals. As they make their way to the sea, rivers help shape the features of the Earth. Rivers are travel routes for people and provide the power for hydroelectric plants.