What is net primary productivity?

Net primary productivity (NPP) refers to the amount of energy that is captured by photosynthetic organisms through the process of photosynthesis and then made available for growth and reproduction after accounting for losses due to respiration and other energy expenditures. In essence, it represents the energy that remains after the plants have used some of it for their metabolic processes. This value is crucial for understanding the energy flow in ecosystems, as it provides an indication of the energy available for herbivores and subsequently for higher trophic levels.

The concept of NPP underscores the efficiency of photosynthetic organisms in converting solar energy into biomass that can be used by other organisms within the food web. In contrast, total productivity does not consider these energy losses, and thus, does not provide an accurate measure of the energy available for consumption by other organisms. The overall productivity of an ecosystem is a broader term and includes both gross primary productivity (GPP) and losses, which can be misleading when looking at ecosystem efficiency. Lastly, the energy available to herbivores after decomposition refers more to the detrital pathway rather than the direct productivity from photosynthetic organisms, failing to capture the essence of net primary productivity.