Earth Metabolism: Net primary productivity
The Earth is breathing. We gauge a Earth’s metabolism based on the rate at which plants absorb carbon dioxide out of the atmosphere.
Net primary productivity is how much carbon dioxide is taken in during photosynthesis minus how much is given off during respiration.
For example, lush tropical rainforests are the most productive places on the planet.
But tundras are least productive because little photosynthesis takes place in polar regions.