Final answer:
An ecosystem is said to have high net primary productivity when it produces a large amount of organic matter, which is often associated with warm and wet climates that support high rates of photosynthesis and biomass production.
Step-by-step explanation:
An ecosystem is said to have high net primary productivity (NPP) when it produces a large amount of organic matter. NPP is the rate at which all the plants in an ecosystem produce net useful chemical energy; it is equal to the difference between the energy that they use to grow and the energy that they produce through photosynthesis. Warm and wet climates are typically associated with high net primary productivity because these conditions allow for optimal photosynthesis and plant growth. Therefore, areas with such climates will have high biomass production and a high amount of organic matter available as food for other organisms. Conversely, ecosystems in regions with dry or cold environments typically exhibit lower levels of photosynthesis and, consequently, lower biomass and net primary productivity.