In recent years, environmental scientists have turned their attention to the total productive capacity of the earth and the share appropriated by Homo sapiens. Such measurements complement other indicators of global stress, such as atmospheric concentrations of greenhouse gases.

The latest and most detailed analysis comes from a group headed by biologist Marc L. Imhoff of the NASA Goddard Space Flight Center. Using satellite and climate data, the team calculated the worldwide amount of solar energy converted to plant organic matter through photosynthesis. This measure, called net primary production (NPP), is the chief source of food for living creatures. (It excludes other forms of energy, such as fossil fuels or seafood.) The researchers then figured out the human share of NPP based on consumption of plant foods, meat, milk, eggs, and wood used as fuel and in construction.

This article was originally published with the title The Lion's Share.

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