I’m trying to understand the timeframe of the risk to humanity from the loss of phytoplankton.
- The mass of the atmosphere is 5.148X10^18kg.
- O2 is currently 20.95% of the Atm or 1.0785X10^18kg
- According to this link OSHA says the minimum safe % of O2 is 19.5% which would put Atmospheric O2 at 1.00386X10^18kg
- Meaning we would have to lose 7.46x10^18kg of O2 before noticing the effects.
So how long would that take?
Per
Wiki the oxygen cycle has balancing gains and losses from all sources of 3X10^14kg per year.
Of that, photo synthesis from the ocean provides 1.35X10^14kg of O2. (For comparison land based photosynthesis provides a bit more at 1.65X10^14kg of O2)
So if we lost all ocean photosynthesis tomorrow it would take about
450 years before we would notice an ill effect (headaches, mental impairments, exhaust quicker than normal). Although I will point out that humans can adapt to lower O2 levels like those who live at high altitudes. So it would likely be longer.
(Death occurs at 6% O2 which would take ~4600 years.)
So how fast are we losing phytoplankton?
From what I can find fast enough that it’s worrying (40% since 1950 at this
link) but nothing that says it will all die off. Not even during studies that assume no mitigation’s and an almost 10C increases in air temps by 2300 (
Link). Mostly the changes force the remaining phytoplankton to migrate into cooler waters.
So while I’m not saying phytoplankton die off isn’t a major problem I’m having trouble seeing it the way you do. If nothing is done large swathes of land will have summer temperatures routinely above 130F making them inhospitable for civilization before we even feel the first effects of dropping O2.
Can you point me to the study that’s got you concerned?