1.1: From biodiversity to the quantitative account of the biomass
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Centuries of observation of nature have led to an increasingly detailed – but still incomplete – picture of the species that inhabit our planet and their respective roles in the various ecosystems (see What is biodiversity?). Since the beginning of the century, several major technological and scientific advances have expanded our understanding of biodiversity on Earth:
- New approaches to genome sequencing have enabled a more detailed view of the composition of many natural communities. By characterizing short fragments of their DNA that persist in the environment, it is thus possible to inventory the biodiversity of an ecosystem from samples of water, soil, etc. (See DNA barcoding to characterize biodiversity) ;
- Recent global sampling efforts, such as those of the Tara Oceans expedition (Figure 1) and its continental counterparts around the world, are providing more robust descriptions of the populations of natural habitats (See When the Tara Oceans expedition explores plankton diversity) ;
- Better remote sensing tools enable to probe the environment on a global scale with unprecedented resolution and specificity. [See for example the NASA Earth Observatory video on ocean phytoplankton: Feeding the Sea: Phytoplankton Fuel Ocean Life]
Figure \(\PageIndex{1}\). On the deck of the schooner Tara during sampling in the Labrador Sea during a sampling station of the Tara Oceans campaign. [Source: photo © Francois Aurat / Tara Expeditions Foundation – NASA Goddard Space Flight Center, CC BY 2.0]
In describing a complex system such as the biosphere, it is critical to quantify the abundance of individual components of the system (i.e., species, broader taxonomic groups…) within the various ecosystems. A quantitative description of biomass distribution is essential for taking stock of biosequestrated carbon [2] and modelling global biogeochemical cycles [3] , as well as for understanding the past and future impact of human activities.
Such a comprehensive quantitative analysis of the biomass of each taxon was recently proposed by an Israeli team [4, 5]: through a meta-analysis of published data, Bar-on et al. have assembled a census of the biomass of all kingdoms of life and have provided a holistic view of the composition of the biosphere on land and in the oceans, a theory or approach that focuses on an object as a whole, as a constituent of a whole. This has allowed the construction of specific models of taxonomic categories, geographical locations and trophic modes. The general framework of this strategy is summarized in the associated focus (See How to estimate global biomass?).