The solar energy captured by the producers dissipates along the food chains in the form of heat, an energy that is not usable by living beings. As this energy is dissipated by the ecosystem, permanent compensation occurs for the use of solar energy set by the producers, then passing through all other living elements of the ecosystem.
The highest energy level in terrestrial ecosystems is chlorophyllated plants (producers). The rest of the ecosystem is entirely dependent on the energy they collect after it is transferred and stored in organic compounds. The immediate level consists of herbivores. A herbivore will therefore get less energy from chlorophyll plants than they receive from the sun. The next level corresponds to that of carnivores. Only part of the energy contained in herbivores will carry over to carnivores and so on.
A process of graphical representation of this energy transfer in ecosystems, called energy pyramid, was adapted, in which the representative area of each trophic level is proportional to the amount of energy available. Thus, the rectangle that represents the amount of energy that transits from producers to first-order consumers is larger than that which represents the energy that passes from producers to second-order consumers and so on.
Food chains are generally limited to 4 or 5 trophic levels because there are very significant energy losses in transfers between different levels. Consequently, the amount of energy reaching the highest levels is no longer sufficient to support yet another trophic level.
It has been estimated that a surface of 40000m2 It can produce rice in adequate conditions to feed 24 people for a year. If this rice, instead of being used as food for man, were used for cattle breeding, the meat produced would feed only one person during the same period.
The shorter a food chain, the more energy will be used. In countries lacking food, man should choose to get it through short chains.
To calculate the efficiency of energy transfers from one level to another, there is a need to assess the amount of organic matter or energy existing at each trophic level, ie, it is necessary to know the productivity throughout the entire ecosystem.