Earth's Carrying Capacity

Thomas Palm wrote:
Ian Stirling wrote in
:

In sci.space.policy Gactimus wrote:
How many people can the earth support?

Multiply the population density of Biosphere II, which could probably
work at that population density, with the area of the earth, and you
get 200 billion.

Biosphere II was never self-sufficient but relied heavily on energy
import,

So does the world. But the energy 'imported' from the sun is much much
greater than all of our use put together, so it is not a limiting factor.

and against the rules had to replace the atmosphere when CO2
levels got too high.

Yes, due to changes in soil balance. This was unexpected but not a factor in
the food balance. The real point was that Biospherians found it hard to
produce enough to eat and exited quite a bit thinner than they went in.

Rand Simberg wrote in
nk.net:

Thomas Palm wrote:

Multiply the population density of Biosphere II, which could probably
work at that population density, with the area of the earth, and you
get 200 billion.


Biosphere II was never self-sufficient but relied heavily on energy
import, and against the rules had to replace the atmosphere when CO2
levels got too high.

There's nothing wrong with energy import. The earth wouldn't survive
for long without energy import.

If you try to calculate the required "footprint" for humans it certainly is
wrong to exclude the area needed for the powerplant. It's like taking the
population density of a major city and pretend you could extend it all over
Earth without considering how cities are dependent on the surrounding
countryside for raw materials and waste disposal.

Ian St. John wrote:

Six billion so far and we have yet to even start farming the
oceans, 70% of the surface of the planet.


My impression is we've halfway farmed them to death.

We don't farm them, we still hunt them.


We do farm them also. This is really the only way to get salmon these days
as the stocks dwindle due to destruction of their streams and their
genetics.
http://www.worldwatch.org/pubs/mag/2003/165/mos/
"Estimated amount of farmed fish produced in 2002 = 52,700,000 metric
tons.
http://www.st.nmfs.gov/st1/fus/current/hilite2002.pdf
"WORLD FISHERIES (Live weight, 2001)
Total catch 287.0 billion pounds (130.2 million metric tons)"

so we farm about (52/(52+130)) * 100 = 28.57 percent of the total fish
production.

Most fish farmed are not in the ocean. I didn't say that we don't farm
fish, just that the ocean fish are hunted, not farmed.

Thomas Palm wrote:

Biosphere II was never self-sufficient but relied heavily on energy
import, and against the rules had to replace the atmosphere when CO2
levels got too high.

There's nothing wrong with energy import. The earth wouldn't survive
for long without energy import.


If you try to calculate the required "footprint" for humans it certainly is
wrong to exclude the area needed for the powerplant. It's like taking the
population density of a major city and pretend you could extend it all over
Earth without considering how cities are dependent on the surrounding
countryside for raw materials and waste disposal.

Yes, but that's a function of power density of the plant.

In article ,
Ian St. John wrote:
If you consider them a farm, then you can apply fertiliser. The majority of
the oceans would bloom with a bit of iron added.

Kind of, sort of, maybe. There have been some experiments done, and the
real story seems to be more complicated than that.

They bred it out because the
Omega 3 oils oxidize more readily and thus do not stay fresh on the shelves
forever. Must take all nutrients out of the food so that nothing will find
it edible, including you and me. But it will look GOOD sitting on the store
shelves.

Hard to avoid when customers demand year-round availability and low cost,
and will (mostly) unhesitatingly buy the cheaper kind without reading the
fine print.

Selective breeding for long shelf life etc. is not some evil conspiracy;
it was done because customers like you and me insist on it, voting with
our wallets in favor of convenience and low price.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Rand Simberg writes:


Most fish farmed are not in the ocean. I didn't say that we don't
farm fish, just that the ocean fish are hunted, not farmed.

Well, it's probably not really feasible to "farm" fish in the
conventional matter. Kinda hard to put a brand on a hering. But we do
try to restock the wild fish.

In article
4.229, Thomas Palm
writes
Ian Stirling wrote in
:

In sci.space.policy Gactimus wrote:
How many people can the earth support?

Multiply the population density of Biosphere II, which could probably
work at that population density, with the area of the earth, and you
get 200 billion.

Biosphere II was never self-sufficient but relied heavily on energy import,
and against the rules had to replace the atmosphere when CO2 levels
got too high.

That's energy import over and above sunlight coming in, isn't it?

And AIUI, it /was/ glassed over, so wouldn't you have to do that to
the whole world to get the same productivity?

Robert Carnegie at home, at large
--
I am fully aware I may regret this in the morning.

In article
, Steve Craig writes
Gactimus wrote in message news:1ywi8f85zxz7.dl
...
How many people can the earth support?

I've heard the figure 10 million thrown around before, but I can, in
no way, remember where I heard that, or the justification thereof.
That would make this post quite pointless now that I think about
it....

hmmm...

Steve

Well, it gives us a chance to talk about the difference between
"million" and "billion" ;-)

(By the way, while the U.S. figure for "billion" is not used
universally, I for one have given up on any other. For one thing,
if anyone has a billion of anything - except for, ironically,
population, and maybe livestock - it would most likely be the
U.S. before anyone else.)

Robert Carnegie at home, at large
--
I am fully aware I may regret this in the morning.

In article ,
Pete Lynn wrote:
Note that current birth rates are artificially low, in the very long
term the evolutionary imperative will adapt to the likes of birth
control, and other such recent mitigating effects.

As in so many other areas, for us there are now selective pressures
arising from culture as well as from biology. The current birth rate is
low and is likely to stay that way, because in an advanced society,
children are a major economic burden on the parents. Given control over
the biology (i.e., contraception), that trumps biological "imperatives".
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

In article ,
Al Jackson wrote:
Issac Asimov has an essay somewhere about population exponential
growth , but he lets humans expand into space ...

Fortunately, exponential growth is not a realistic model for human
populations. A letter in Science a little while back pointed out that we
recently passed a major milestone: half the population of Earth now lives
in countries whose fertility is below replacement level.

(World population continues to grow because most of the countries that are
below replacement level are not *far* below it, while many of the
countries that are above it are quite considerably above it. But the
trends are the right way. Barring major surprises, Earth's population
will peak late in this century and then start to decline. The tricky part
is going to be making it through this century -- including the transition
of the Third World to advanced industrial societies -- without too many
unpleasant surprises.)
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |