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Biomass (Rev #4)



As defined by Wikipedia:

Biomass, in ecology, is the mass of living biological organisms in a given area or ecosystem at a given time. Biomass can refer to species biomass, which is the mass of one or more species, or to community biomass, which is the mass of all species in the community. It can include microorganisms, plants or animals. The mass can be expressed as the average mass per unit area, or as the total mass in the community.

How biomass is measured depends on why it is being measured. Sometimes the biomass is regarded as the natural mass of organisms in situ, just as they are. For example, in a salmon fishery, the salmon biomass might be regarded as the total wet weight the salmon would have if they were taken out of the water. In other contexts, biomass can be measured in terms of the dried organic mass, so perhaps only 30% of the actual weight might count, the rest being water. For other purposes, only biological tissues count, and teeth, bones and shells are excluded.

In stricter scientific applications, biomass is measured as the mass of organically bound carbon (C) that is present. The total live biomass on earth is about 560 billion tonnes C, (see See Groombridge et al) and the total annual primary production of biomass is just over 100 billion tonnes C/yr.


The total global live biomass has been estimated as 560 billion tonnes C, most of which is found in forests.


Most of this biomass is found on land, with only 5 to 10 billion tonnes C found in the oceans.

On land there is about 1,000 times more plant biomass (phytomass) than animal biomass (zoomass). About 18% of this plant biomass is eaten by the land animals. However in the ocean the animal biomass is nearly 30 times larger than the plant biomass. Most ocean plant biomass is eaten by the ocean animals.

biomass table

The total biomass of bacteria is estimated to equal that of plants. The number of prokaryotes on Earth is estimated to be around five million trillion trillion, or 5×10 305 \times 10^{30}, accounting for at least half the global biomass.


  • Biomass, Wikipedia.

  • B. Groombridge and M. D. Jenkins, Global Biodiversity: Earth’s Living Resources in the 21st century, World Conservation Monitoring Centre, World Conservation Press, Cambridge, 2011, page 11.

category: ecology