Net primary productivity is defined as gross primary productivity minus respiration loss (R).
NPP = GPP – R
Net primary productivity is the available biomass for the consumption of heterotrophs i.e., both herbivores and decomposers.
The annual NPP of the whole biosphere is approximately 170 billion tons (dry weight) of organic matter. Of this, despite occupying about 70% of the surface, the productivity of oceans is only 55 billion tons and of the terrestrial system is 115 billion tons.