Without doubt, humans affect the ecosystems that they come in contact with. I describe one instance, negative or positive, in which humans have affected the ecosystems.© BrainMass Inc. brainmass.com October 9, 2019, 4:42 pm ad1c9bdddf
With these sorts of questions you are often best using local examples. I'm in the UK and I'm assuming you are somewhere in North America, so I'll try to give a global example- please adapt appropriately for your answer.
It's often quite easy to think of examples where human activities have had a negative effect on ecosystems. To be honest currently the impact of human activities on ecosystems is overwhelming.
An example of a major effect is deforestation. Eg in the Amazon rainforest.
For thousands of years humans have cut down trees and used the land for agriculture. It is now estimated ...
Deforestation is illustrated in the solution.