The fertile land which was good for growing wheat.
Answer:
A) the Indo-Aryan religious system
The French wanted the debt that America owed them back. However, since the previous government (the one that lent them the money) was overthrown, the president said that the debt didn't count anymore. Because of this, French sailors kidnapped and attacked American sailors. This lead to an undeclared, cold war called the Quasi Wars.
The answer is Human
While the other options are always affecting the ecosystems, humans have a greater affect than all of the above