Answer:
First, the activity that humans execute that affects their ecosystem positively is reforestation. Second, the activity that humans execute that affects their ecosystem positively is hunting. Their effects rely completely in nature, however, one improves the ecosystem by making it greener and increasing the space nature has to grow, while the other impacts the ecosystem negatively by unbalancing the food chain.
Step-by-step explanation:
The reasons behind this answer are that in the first place the ecosystem is a very sensitive environment that can be affected by a wide range of factors. In the first place, reforestation helps the environment have better conditions for the animals that live in it, as well as to provide the human race a better quality of air, water and feel better after living in a more natural ecosystem. While hunting breaks the ecosystem's balance because it allows the food chain of the ecosystem to break and allow a general modification.