It is impossible to know exactly how much oxygen is needed to sustain people and the number of people it will sustain as each and every person requires a different amount of oxygen.
Exactly? As in the
precise number of oxygen
molecules required? No, you're right, they don't know
exactly how much oxygen is needed to sustain people.
However, as a practical matter, they do know,
exactly.
There's this thing called the International Space Station where they know
exactly how much oxygen is required for the number of people on board, varying from 3 to 7 generally, and how long it will last. The life support system on the ISS is a mini version of the life support system on Earth.
On Earth, plants, algae, cyanobacteria and phytoplankton all split water molecules as part of photosynthesis - the process that converts sunlight, carbon dioxide and water into sugars for food. The hydrogen is used for making sugars, and the oxygen is released into the atmosphere. On the ISS the same thing occurs, except it's a mechanical photosynthesis process called electrolysis that splits the water molecules, and instead of using the hydrogen molecules to make sugars the hydrogen is either vented to space or it is reclaimed and combined with excess carbon dioxide from the air in a chemical reaction that produces water and methane, and the methane is vented to space. The chemical-mechanical systems in the ISS are much more compact, less labor intensive, and more reliable than a plant-based system, because they can produce exactly the right amount of oxygen to sustain people.
They don't produce more oxygen than they need because doing so is a waste of energy and oxygen, and they don't produce less than they need for clearly obvious reasons. They produce exactly the right amount depending on how many people they have on board.
See above.
refute, verb; to prove to be false or erroneous,
As you state this study is 30 plus years old. It is merely a snapshot in time.
As I also stated, the numbers on that table have been replicated and verified several times over the years, so no, it's not merely a snapshot in time, it's a snapshot that has been verified to still be accurate today.
The table showing the NPP per ecosystem shows, quite correctly, that most of the NPP is derived from the Oceans.I would add that it is specifically Plankton that provide this product, the volume of which is decreasing daily.
Has the volume of plankton ever decreased before? Has it ever been even far less than it is now? The answers to those questions will clue you in that the current state of plankton diminishment might not be the crisis that some are making it out to be.
To say that population will level off at 9 or 10 Billion or whatever arbitrary number is placed on it, based on this exercise, does not suggest that people will not be engaging in the behavior required for reproduction. The behavior will continue. For the population to level off indicates some type of carnage later. I say nip it in the bud now.
You wrongly assume it's an arbitrary number. It's not. It's a number derived by the math of of the known variables, on computer models (air, water, land, food), and on the observations and experimentation with other populations. Populations always expand to that which is sustainable, and then it levels off or is reduced. There is no reason to think the human population will be any different.
