What could be a change that happens upstream that could affect the rest of the ecosystem

Pollution upstream (on a river) could poison many animals in the area, as they drink the polluted water which is not safe for them.

Although this may be the opposite of what you think i will say it anyway. you were brought into this world for a reason and you still have soo much ahead of you. not everybody has an opportunity of living a great life, but it doesn’t give you a reason to end everything. somebody in the world loves you, and imagine what you would do to them if you left forever.