Flow of energy through the ecosystem is a fundamental process, which can be easily quantified if the energy input to the ecosystem and its subsequent transformation from one tropic level to another can be expressed in terms of calories.

Study of ecosystem energetic gives a sound basis for energy budget at individual, population and ecosystem level. We can get a scientific basis for evaluating efficiency of different tropic levels in an ecosystem and comparing diverse ecosystems by quantifying the energy flow.

The first step of energy flow is easiest to measure; that is why several studies are devoted to primary productivity. The incoming solar energy can be monitored with instruments such as a net radiometer, which measures the total radiant energy; or a pyranometer /solarimeter, which only measures the visible light energy. In aquatic ecosystems, the primary production can be measured by following the changing oxygen or carbon dioxide levels in water.

At higher trophic levels, measurement of energy flow involves determination of energy quantity for every species population in each trophic level, and then addition of these specific figures to give the overall energy flow for the trophic level. Because of the enormity of this job, investigation is often limited to studying the energy budget of a single species of animal in a community. The weight, food intake, faecal output and respiration of a few individuals are measured and their assimilation and production rates are calculated.


Human intervention in natural ecosystem is growing significantly. Human impact on the pattern and quantum of energy flow has changed significantly because of the considerable amounts of fossil fuel used by urban, industrial and rural communities.

A good idea of the pattern of energy flow studies conducted by Odum, a noted ecologist (1957) in Silver Springs, Florida. Most of the energy input is in the form of solar radiation. Waste heat dissipated from the system represents energy output. It is observed that the total energy input amounts to 410486 kcal/m2/yr (410,000 kcal/m2/yr of solar energy and 486 kcal/m2/yr in the form of organic matter imported into the system). It exactly matches the output of energy, 407986 kcal/m2/yr is lost as waste heat and 2500 kcal/m2/yr is exported from the system in the form of organic matter. Silver Springs Florida represent a balanced ecosystem in terms of ecological energetic. Thus, energy enters the ecosystem as free solar energy and leaves it as heat, having undergone changes from a concentrated to a dispersed state. Studies of energy flow are very important in understanding ecosystem functioning and its rational management.