Point is a direct source of pollution. Landfills, gasoline, and chemical plants would be examples of point source pollution. Non-point can be vehicles.
So they both pollute, but point comes straight from something. Non-point is pollution going off from something.
If vegatation were to decrease then primary consumers that are herbivores which are usually the prey will start to decrease too, because there food source is becoming limited. It's like a domino effect, if something is unbalanced in the ecosystem then the whole ecosystem could collapse.
Accio crab, Ancient otter, Skywalker gibbon Thats all I know anyways hope this helps