Q1.
What if … photosynthesis stopped, what would happen on the Earth?
Answer
Two supplies would fail almost at once — food and oxygen — and the whole living world would collapse from the bottom of the food chain upwards.
Photosynthesis: 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2
Stop it and you remove, simultaneously:
• the only large-scale source of glucose — the food of nearly all life
• the only large-scale source of free O2 in the atmosphere
• the only large-scale removal of CO2 from the air
Stop it and you remove, simultaneously:
• the only large-scale source of glucose — the food of nearly all life
• the only large-scale source of free O2 in the atmosphere
• the only large-scale removal of CO2 from the air
The sequence of events:
- Producers die first. Green plants, algae and phytoplankton have no way to make food and are exhausted within days.
- Herbivores starve, then carnivores. Every food chain in the book begins at a producer, so the loss travels upward through every trophic level.
- Oxygen falls. Respiration by animals and microbes, and the combustion of fuels, keep using O2. With no photosynthesis to restore it, the 21% oxygen in the atmosphere is steadily drawn down. Aerobic life fails; only some anaerobic microbes survive.
- CO2 builds up. Respiration, decomposition and combustion keep releasing CO2 with nothing to absorb it, so the greenhouse effect intensifies and the Earth grows hotter.
- The carbon and oxygen cycles both break. The chapter defines the oxygen cycle as the balance between consumption (respiration and combustion) and production (photosynthesis). Remove production and there is no cycle left, only a one-way loss.
Did you know? Most of this work is not done by forests. Microscopic phytoplankton in the oceans carry out a huge share of the world's photosynthesis. That is why ocean acidification and warming, which threaten plankton, matter to the air you breathe on land.