In what ways can humans change an ecosystem?

Humans can change ecosystems in many ways such as helping with pollution, another example is people can remove trees, change the flow of water, and change grasslands into farms.

Explanation:

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.