What does the '10% rule' in ecology refer to?

The '10% rule' in ecology refers to the concept that when energy is transferred from one trophic level to the next in an ecosystem, generally only about 10% of the energy is passed on to the next level. This means that during each transfer of energy (e.g., from plants to herbivores, or from herbivores to carnivores), a significant amount of energy is lost, primarily as heat through metabolic processes and as a result of other life activities such as movement, reproduction, and maintenance of body functions.

This rule highlights the inefficiency of energy transfer within food webs, illustrating why fewer organisms can be supported at higher trophic levels. It underscores important ecological concepts such as energy flow, trophic dynamics, and ecosystem productivity, showing that as one moves up the food chain, energy availability diminishes substantially. This principle is foundational for understanding population dynamics and the structure of ecosystems.