The 10% rule, a fundamental concept in ecology, describes the energy transfer between trophic levels in food chains and food webs. This principle states that, on average, only about 10% of the energy consumed by organisms at one trophic level is passed on to the next higher level.

To elaborate, the 10% rule is based on the observation that a significant portion of energy is lost during the processes of consumption, digestion, and metabolism, with most of it dissipated as heat. Consequently, this results in a limited amount of energy being available for the next trophic level.

For instance, if a plant (the producer) captures $1000$ units of energy from sunlight, a herbivore (the primary consumer) that feeds on this plant will only obtain approximately $100$ units of energy. Following this pattern, a carnivore (the secondary consumer) that preys on the herbivore will receive around $10$ units of energy. This energy transfer continues up the food chain, creating a pyramid-like structure where energy is most abundant at the base and diminishes at the top, where apex predators reside.

Understanding the 10% rule is essential for grasping the structure and dynamics of ecosystems. It explains the typical observation of fewer organisms at higher trophic levels and the decrease in biomass from the base to the apex of the food chain. Additionally, this principle underscores the inefficiency of energy transfer between trophic levels, which has significant implications for human food production and resource management. For example, it suggests that consuming lower trophic levels, such as adopting a plant-based diet, is generally more energy-efficient and sustainable compared to diets that rely heavily on higher trophic levels, like meat consumption.

It’s important to note, however, that the 10% rule serves as a rough estimate and can vary based on the specific ecosystem and the organisms within it. Factors such as the type of food consumed, the efficiency of digestion, and the metabolic rates of organisms can all influence the energy transfer between levels. Despite these variations, the 10% rule remains a valuable framework for studying energy flow in ecosystems.