---
title: "Biomass (ecology)"
chunk: 1/3
source: "https://en.wikipedia.org/wiki/Biomass_(ecology)"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T07:17:15.767962+00:00"
instance: "kb-cron"
---

Biomass is the total mass of living biological organisms in a given area or ecosystem at a specific time. Biomass may refer to the 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 encompasses microorganisms, plants, and animals, and is typically expressed as total mass or average mass per unit area.
The method used to measure biomass depends on the context. In some cases, biomass refers to the wet weight of organisms as they exist in nature. 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. In other contexts, it may refer to dry weight (excluding water content), or to the mass of organic carbon, excluding inorganic components such as bones, shells, or teeth.
In 2018, Bar-On et al. estimated Earth's total live biomass at approximately 550 billion tonnes of carbon, the majority of which is found in plants. A 1998 study by Field et al. estimated global annual net primary production at just over 100 billion tonnes of carbon per year. While bacteria were once believed to account for a biomass comparable to that of plants, more recent research indicates they represent a much smaller proportion. The total number of DNA base pairs on Earth – sometimes used as a possible approximation of global biodiversity – has been estimated at (5.3±3.6)×1037, with a mass of around 50 billion tonnes. By the year 2020, the mass of human-made materials or anthropogenic mass, defined as "the mass embedded in inanimate solid objects made by humans (that have not yet been demolished or taken out of service)", was projected to surpass that of all living biomass on Earth.

== Ecological pyramids ==

An ecological pyramid is a graphical representation that shows, for a given ecosystem, the relationship between biomass or biological productivity and trophic levels.

A biomass pyramid shows the amount of biomass at each trophic level.
A productivity pyramid shows the production or turn-over in biomass at each trophic level.
An ecological pyramid provides a snapshot in time of an ecological community.
The bottom of the pyramid represents the primary producers (autotrophs). The primary producers take energy from the environment in the form of sunlight or inorganic chemicals and use it to create energy-rich molecules such as carbohydrates. This mechanism is called primary production. The pyramid then proceeds through the various trophic levels to the apex predators at the top.
When energy is transferred from one trophic level to the next, typically only ten percent is used to build new biomass. The remaining ninety percent goes to metabolic processes or is dissipated as heat. This energy loss means that productivity pyramids are never inverted, and generally limits food chains to about six levels. However, in oceans, biomass pyramids can be wholly or partially inverted, with more biomass at higher levels.

== Terrestrial biomass ==

Terrestrial biomass generally decreases markedly at each higher trophic level (plants, herbivores, carnivores). Examples of terrestrial producers are grasses, trees and shrubs. These have a much higher biomass than the animals that consume them, such as deer, zebras and insects. The level with the least biomass are the highest predators in the food chain, such as foxes and eagles.
In a temperate grassland, grasses and other plants are the primary producers at the bottom of the pyramid. Then come the primary consumers, such as grasshoppers, voles and bison, followed by the secondary consumers, shrews, hawks and small cats. Finally the tertiary consumers, large cats and wolves. The biomass pyramid decreases markedly at each higher level.
Changes in plant species in the terrestrial ecosystem can result in changes in the biomass of soil decomposer communities. Biomass in C3 and C4 plant species can change in response to altered concentrations of CO2. C3 plant species have been observed to increase in biomass in response to increasing concentrations of CO2 of up to 900 ppm.

== Ocean biomass ==

Ocean or marine biomass, in a reversal of terrestrial biomass, can increase at higher trophic levels. In the ocean, the food chain typically starts with phytoplankton, and follows the course:

Phytoplankton → zooplankton → predatory zooplankton → filter feeders → predatory fish