Net primary productivity (NPP) is the amount of C or biomass that accumulates over time and is photosynthesis—autotroph respiration. Annual NPP is estimated by summing positive biomass increments across time periods during the growing season, including offtake to herbivores, which can be high in grasslands. Remote sensing techniques that are used to assess NPP are discussed by the author. Belowground productivity can be high in grasslands, and it is important to carbon storage. Across grasslands on a geographic scale, NPP, N mineralization, and soil organic C all increase with annual precipitation. Within regions, NPP can be strongly affected by the proportion of C4 plant species and animal species composition and diversity. Humans are adding more N to the environment than all the natural forms of addition (fixation and lightning) combined. Animals, especially herbivores, can have strong effects on how plants respond to changes in changes in resource availability.