The sun does not move or rotate and hence cannot retrograde, however the other planets rotate. Some astronomers define retrograde motion as the Westward movement of the planets relative to the sun, based on this definition, all the planets experience retrograde movement. On the other hand, while some astronomers define retrograde motion as the movement that the other planets make when earth passes them while orbiting the sun. Based on this second classification, Mercury and Venus do not retrograde relative to the earth because they move faster than the earth.
I think your answer would be biomass. If the earth uses too much of it, it will take too long to replenish. Hope this helped could I possibly get brainliest?