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Amount of sunlight is not the limiting factor on plant growth in most places. In fact, it's often the opposite - plants shut down respiration during midday to l

Amount of sunlight is not the limiting factor on plant growth in most places. In fact, it's often the opposite - plants shut down respiration during midday to limit water loss because it's too hot.

mchannon 9y ago
I imagine "most places" refers to most places on land, which is less than 20% of the range of where plants grow. Ocean-based plantlife is the workhorse on this planet, and I would argue that the lion's share is absolutely constrained by available sunlight. Further, there's a substantial difference between "respiration" and absorption of sunlight. Pineapple plants, for instance, only "breathe" at night.
- tlb 9y ago
  Plant life in the oceans is mainly limited by minerals, especially iron. That's why the oceans aren't green and slimy. Dumping iron powder in will usually cause an algae bloom, which eventually die and take the carbon they fixed to the bottom, so seeding the oceans with iron is a potential way of reducing CO2 in the atmosphere. Of course, like any large-scale meddling, there will be collateral damage.
  - 6502nerdface 9y ago
    > will usually cause an algae bloom, which eventually die and take the carbon they fixed to the bottom It works so well that this could even be how the current "icehouse earth" conditions got started in the first place. The Azolla bloom of 49 ma dropped atmospheric CO2 levels from 3500ppm to 650ppm in less than 1 my, and CO2 has been in that lower range ever since. https://en.m.wikipedia.org/wiki/Azolla_event https://en.m.wikipedia.org/wiki/Azolla_event
- jws 9y ago
  A quick, non-biologist's googling suggests that nitrate and ammonium are the limiting factors for most oceanic algae. I recall there being experiments for areas are iron limited, so they spread iron sulfate and created algae blooms. I suppose intuitively, if you scoop up a bucket of ocean water, it is not green. If light were the limiting factor you would expect the water to contain lots of light absorbing algae. This does happen in nutrient rich waters, like the sewage lagoons and creeks I grew up near.

Amount of sunlight is not the limiting factor on plant growth in most places. In fact, it's often the opposite - plants shut down respiration during midday to limit water loss because it's too hot.

mchannon 9y ago

I imagine "most places" refers to most places on land, which is less than 20% of the range of where plants grow. Ocean-based plantlife is the workhorse on this planet, and I would argue that the lion's share is absolutely constrained by available sunlight. Further, there's a substantial difference between "respiration" and absorption of sunlight. Pineapple plants, for instance, only "breathe" at night.

tlb 9y ago
Plant life in the oceans is mainly limited by minerals, especially iron. That's why the oceans aren't green and slimy. Dumping iron powder in will usually cause an algae bloom, which eventually die and take the carbon they fixed to the bottom, so seeding the oceans with iron is a potential way of reducing CO2 in the atmosphere. Of course, like any large-scale meddling, there will be collateral damage.
- 6502nerdface 9y ago
  > will usually cause an algae bloom, which eventually die and take the carbon they fixed to the bottom It works so well that this could even be how the current "icehouse earth" conditions got started in the first place. The Azolla bloom of 49 ma dropped atmospheric CO2 levels from 3500ppm to 650ppm in less than 1 my, and CO2 has been in that lower range ever since. https://en.m.wikipedia.org/wiki/Azolla_event https://en.m.wikipedia.org/wiki/Azolla_event
jws 9y ago
A quick, non-biologist's googling suggests that nitrate and ammonium are the limiting factors for most oceanic algae. I recall there being experiments for areas are iron limited, so they spread iron sulfate and created algae blooms. I suppose intuitively, if you scoop up a bucket of ocean water, it is not green. If light were the limiting factor you would expect the water to contain lots of light absorbing algae. This does happen in nutrient rich waters, like the sewage lagoons and creeks I grew up near.