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Why is less energy available at higher levels of a trophic pyramid?

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Zenaida macroura: mouring doves — ecology Mourning doves (*Zenaida macroura*) on their nest protected within the prickly branches of a cactus in the Sonoran Desert, Arizona, U.S.

In an ecosystem, less energy is available at higher levels of a trophic pyramid primarily because energy transfer between levels is inefficient.12

As energy flows through a food chain, a significant portion—often 80 to 90 percent—is lost to the environment as heat. This loss occurs because organisms must expend energy on essential metabolic processes, such as digestion, movement, and maintaining body temperature.23

This phenomenon is a biological application of the second law of thermodynamics, which dictates that energy transformations are never 100 percent efficient and that some energy is inevitably dissipated as waste heat, increasing the entropy of the system. Consequently, only a small fraction of the energy consumed at one level is converted into new biomass that can be utilized by the next level of consumers. Because of this cumulative loss, the amount of available energy decreases significantly as you move up the pyramid from primary producers to higher-order consumers.456123