due to photosynthesis. Global primary production can be estimated from satellite observations. Satellites scan the normalised difference vegetation index (NDVI) over terrestrial habitats, and scan sea-surface chlorophyll levels over oceans. This results in 56.4 billion tonnes C/yr (53.8%), for terrestrial primary production, and 48.5 billion tonnes C/yr for oceanic primary production. Thus, the total photoautotrophic primary production for the Earth is about 104.9 billion tonnes C/yr. This translates to about 426 gC/m2/yr for land production (excluding areas with permanent ice cover), and 140 gC/m2/yr for the oceans. However, there is a much more significant difference in standing stocks—while accounting for almost half of total annual production, oceanic autotrophs account for only about 0.2% of the total biomass. Autotrophs may have the highest global proportion of biomass, but they are closely rivaled or surpassed by microbes. Terrestrial freshwater ecosystems generate about 1.5% of the global net primary production. Some global producers of biomass in order of productivity rates are See also Biomass partitioning - a biomass manipulation study References Further reading External links The mass of all life on Earth is staggering — until you consider how much we’ve lost Counting bacteria Trophic levels Biomass distributions for high trophic-level fishes in the North Atlantic, 1900–2000 Ecology terminology Environmental terminology Ecological metrics Ecosystems Fisheries science