Well if we think about a food pyramid there are consumers that eat plants and if there are no plants to eat then those primary consumers die. Which means that the secondary consumers have no prey to eat and die as well, eventually leading to the top predators who have absolutely nothing to feed on.
They are the most affected because energy level decreases the higher up you go so the top predators need to eat more and if there is less and less to eat they die out quicker
