humans destroying their homes and killing them and their resources. (food, mating grounds, etc)
Humans
You'd have to be more specific about when, but the most likely answer is the Persian Empire, led by Darius III.
threatening
It is not life threatening if it is minor.
Climate change is causing the Arctic ice to melt, which is affecting polar bears' ability to hunt for food and survive. This is leading to a decline in their population and threatening their existence.
He had a life-threatening illness.
YES!!!!!! it is very life threatening!
Her threatening demeanor made me decide to change the subject.
Yes, alcoholism can be a life-threatening disease.
No, nothing is threatening the Falls.
Heat stroke is immediately life threatening.
to be true a non threatening emergency is when you have a problem but it isn't a life or death problem