An object's inertia is its tendency to maintain contact: 1.) Mass.
2.) Position.
3.) Acceleration.
4.) Velocity.

hello! it is velocity.

i say this because, Inertia is the tendency of an object to resist changes in its state of motion. ... The state of motion of an object is defined by its velocity - the speed with a direction.

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide