by David Spratt
| Deforestation in the Brazilian Amazon. Image: Chatham House | |
The plant-based terrestrial biosphere may be understood as including the world’s land-based plants, soils, derived dead organic matter, such as litter, and soil organic matter.
Plants photosynthesis uses carbon dioxide and water to produce sugar (glucose) and oxygen. Around 30% of the additional carbon dioxide (CO₂) produced by human actions has been drawn down from the atmosphere (mitigated) by increased plant photosynthesis. This adds to the land-based sink of stored carbon. But plants also respire, for example at night and in winter, by converting oxygen and stored glucose back into water and carbon dioxide.
As the planet continues to warm, a point of warming is reached — the “thermal maximum for photosynthesis” — after which combination of the rate of photosynthesis decreasing and the rate of respiration increasing results in the net flux of CO₂ from the atmosphere decreasing.











