The biomass distribution on Earth

Abstract

A census of the biomass on Earth is key for understanding the structure and dynamics of the biosphere. However, a global, quantitative view of how the biomass of different taxa compare with one another is still lacking. Here, we assemble the overall biomass composition of the biosphere, establishing a census of the ≈550 gigatons of carbon (Gt C) of biomass distributed among all of the kingdoms of life. We find that the kingdoms of life concentrate at different locations on the planet; plants (≈450 Gt C, the dominant kingdom) are primarily terrestrial, whereas animals (≈2 Gt C) are mainly marine, and bacteria (≈70 Gt C) and archaea (≈7 Gt C) are predominantly located in deep subsurface environments. We show that terrestrial biomass is about two orders of magnitude higher than marine biomass and estimate a total of ≈6 Gt C of marine biota, doubling the previous estimated quantity. Our analysis reveals that the global marine biomass pyramid contains more consumers than producers, thus increasing the scope of previous observations on inverse food pyramids. Finally, we highlight that the mass of humans is an order of magnitude higher than that of all wild mammals combined and report the historical impact of humanity on the global biomass of prominent taxa, including mammals, fish, and plants.

Keywords: biomass; biosphere; ecology; quantitative biology.

Fig. 1.

Graphical representation of the global biomass distribution by taxa. (A) Absolute biomasses of different taxa are represented using a Voronoi diagram, with the area of each cell being proportional to that taxa global biomass (the specific shape of each polygon carries no meaning). This type of visualization is similar to pie charts but has a much higher dynamic range (a comparison is shown in SI Appendix, Fig. S4). Values are based on the estimates presented in Table 1 and detailed in the SI Appendix. A visual depiction without components with very slow metabolic activity, such as plant stems and tree trunks, is shown in SI Appendix, Fig. S1. (B) Absolute biomass of different animal taxa. Related groups such as vertebrates are located next to each other. We estimate that the contribution of reptiles and amphibians to the total animal biomass is negligible, as we discuss in the SI Appendix. Visualization performed using the online tool at bionic-vis.biologie.uni-greifswald.de/.

Fig. 2.

Biomass distributions across different environments and trophic modes. (A) Absolute biomass is represented using a Voronoi diagram, with the area of each cell being proportional to the global biomass at each environment. Values are based on SI Appendix, Table S23. We define deep subsurface as the marine subseafloor sediment and the oceanic crust, as well as the terrestrial substratum deeper than 8 m, excluding soil (6). (B) Fraction of the biomass of each kingdom concentrated in the terrestrial, marine, or deep subsurface environment. For fungi and protists, we did not estimate the biomass present in the deep subsurface due to data scarcity. (C) Distribution of biomass between producers (autotrophs, mostly photosynthetic) and consumers (heterotrophs without deep subsurface) in the terrestrial and marine environments. The size of the bars corresponds to the quantity of biomass of each trophic mode. Numbers are in gigatons of carbon.

Fig. 3.

General framework for estimating global biomass. The procedure begins with local samples of biomass across the globe. The more representative the samples are of the natural distribution of the taxon biomass, the more accurate the estimate will be. To move from local samples to a global estimate, a correlation between local biomass densities and an environmental parameter (or parameters) is established. Based on this correlation, in addition to our knowledge of the distribution of the environmental parameter, we extrapolate the biomass across the entire globe. The resolution of the resulting biomass distribution map is dependent on the resolution at which we know the environmental parameter. Integrating across the entire surface of the Earth, we get a global estimate of the biomass of the taxon.