What characteristic explains why food webs rarely have more than four or five trophic levels?

Answer

The rapid, successive decline in available energy at each step.

The massive loss of available energy due to inefficiency at each transfer step causes the energy supply to decline so rapidly that food webs seldom sustain more than a few trophic levels.

What characteristic explains why food webs rarely have more than four or five trophic levels?
EcologyEcosystemenergyfood webtrophic level