29-06-2005 05:58									#91
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quote: Originally posted by Kuciwalker Say a bunch of predators are wiped out by a plague. The prey then survive and reproduce more, providing more food for the remaining predators. This makes the predator population increase, returning the system to equilibrium.

That is true when you are looking at a specific part of the planet, but the planet as a whole doesn't have such a built-in.

	29-06-2005 06:14									#92
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quote: Originally posted by BlackCat That is true when you are looking at a specific part of the planet, but the planet as a whole doesn't have such a built-in.

it almost has to or it would have tipped far enough away from equillibrium to wipe out all life multiple times in the last few billion years. Over those time scales earth has been subject to some immense insults.

	29-06-2005 06:15									#93
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The environment does, though, individually and collectively.

	29-06-2005 06:34									#94
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quote: Originally posted by Geronimo it almost has to or it would have tipped far enough away from equillibrium to wipe out all life multiple times in the last few billion years. Over those time scales earth has been subject to some immense insults.

Not nessecarily. It is true that the wipeout of one predator may give another a chance, but that is still local.

The only reason that there is a kind of balance on earth is that it have a relatively stable position in it's orbit around the sun.

	29-06-2005 06:51									#95
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Remember the subject matter of this thread. We only have to wipe out one species: mankind.

	29-06-2005 06:56									#96
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quote: Originally posted by Zkribbler Remember the subject matter of this thread. We only have to wipe out one species: mankind.

Well, then I'll suggest the visit of a black hole - that should end all discousions .

	29-06-2005 11:25									#97
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quote: You ever heard of the bacteria-in-petri-dish experiment?

One of the most fundamental assumptions of Malthus is that the curve of population growth and food production are in fact independent of each other.

I wrote a long essay on one of Malthus' contemporaries, Simon Gray, who argued that they are in fact related to each other. Food demand is inelastic, so there is little drive to cultivate beyond what is needed to feed the population. If the population grows, then the price of food will go up, thus making more of an incentive to cultivate more marginal terrain.

The second factor is the technological improvements into cultivation, which is also somewhat dependent on population growth, since if food costs more, there is more incentive to become more efficient in the space that you cultivate.

None of these are true in the bacteria and petri dish argument, since the bacteria cannot increase their food supply.

	29-06-2005 11:29									#98
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quote: But why the curve? If it settles down to zero-growth, the simple problem of finite resources will send numbers falling, see above post.

If you read the article they are not talking about settling down to zero growth, but about decline. Rather than settling down, they estimate fertility rates to drop to around 1.4 children per women. This will, if sustained for a long enough period, inevitably produce a drop in the population. Life expectancy masks the effect of the fertility decline, as does immigration, but immigration is a zero sum game in the worldwide sense.

	29-06-2005 15:27									#99
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quote: Originally posted by Kuciwalker You don't understand the meaning of the term. In a stable equilibrium, there are built-in forces that tend to return the system to the equilibrium state.

Well it should rather be "an equilibrium state",
as altering of the environment could mean that the model returns oto another equilibrium state with other physical parameters than before (for example another c(CO2)) and not all equilibria the system can take might be suited for humans to exist (early earth for example (without plants and animals) could also be considered as being in a stable state of equilibrium, but humans wouldn´t survive there

But it doesn´t contradict the thing I said about crontol circuits, so I might explain further:
You could see the mass of trees (and their growth) on earth as one (of many) control circuits which lower atmospheric c(CO2) (of course trees also might be seen as part of many other control circuits ).
If you fell the trees, less CO2 gets absorbed which causes other control circuits to react (for example as probably more CO2 gets into the seawater it might the algae there to grow faster) therefore again causing them to consume more CO2 and so on.
Teh growth of algae on the other hand has a certain influence on other animals and plants and physical parameters (be creating oxygen, consuming CO2, nutritients and other things and being itself part of a food chain). And these other animals and plants could also be control circuits for certain physical parameters.

Now normally, if there was just a single push one year (for example trees being felled just in one year) or being a push, which probably has no Effect on other control circuits (for example because [mass of trees being felled/year] <= [mass of tree growth / year] ) GAIA might de facto return to a stable equilibrium within years or decades .
But as there are constant pushes, i.e. (in case of CO2) a yearly loss of tree mass (because [mass of trees being felled/year] > [mass of tree growth / year] (at least so I assume )) coupled with (human generated) CO2 Outputs which grow every year,
the system (or at least parts of it) might have no chance to return to a fully stable equilibrium (as maybe also some parts within the system might take decades to adapt to altered conditions and get into equilibrium again).
Despite looking stable to the outside the system might become inherently more instable with every year,
up to a point, where finally an additional single small push (just like the butterfly of chaos theory ) is enough to have great effects among the system
(effects which the small push wouldn´t have been able to cause, if there wouldn´t have been a lot of small pushes before)

	29-06-2005 15:36									#100
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quote: Originally posted by Geronimo likely your virus' high mutation rate would spoil the elaborate incubation mechanism when a mutated strain that lacks the incubation rate would jump the gun and blow the secrecy. If the mutation rate of a virus is high it's almost impossible to have the insidious unseen spread of the disease you are counting on to take out the whole species without any warning. The high mutation rate will also likely moneky wrench the silent animal carrier model.

Yes, that´s sadly true,
mutations could alter any of the attributes I mentioned
and might even render the virus (or at least some strains which might develop) absolutely harmless to humans.

Maybe I should drop the high mutation rate.
As I count on stealth and rapid spread of the virus,
a high mutation rate might not be necessary,
as (hopefully) no one will detect it (and develop drugs against it) before it is too late

	01-07-2005 19:34									#101
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one of the combinations in the downfall of our spiecies has had a recent scientific report published:

http://news.bbc.co.uk/1/hi/sci/tech/4633681.stm

Once our seas are toxic enough, then a whole level of the food chain will bottom out. These things cant be looked at in pure isolation either as each detrimental effect we make on our planets systems has a knock on effect in others.

	01-07-2005 22:18									#102
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How does acidity disipate naturally? In the past greenhouse gasses have been 250X current levels and yet the acidity is what it is today. There must be a way nature corrects the problem.

	02-07-2005 04:46									#103
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quote: Originally posted by child of Thor one of the combinations in the downfall of our spiecies has had a recent scientific report published: http://news.bbc.co.uk/1/hi/sci/tech/4633681.stm Once our seas are toxic enough, then a whole level of the food chain will bottom out. These things cant be looked at in pure isolation either as each detrimental effect we make on our planets systems has a knock on effect in others.

Toxic food wouldn't wipe us out, it would just make food taste bad and be very expensive as the human race would subsist on de-toxified processed foods.

	02-07-2005 04:52									#104
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quote: Originally posted by child of Thor one of the combinations in the downfall of our spiecies has had a recent scientific report published: http://news.bbc.co.uk/1/hi/sci/tech/4633681.stm Once our seas are toxic enough, then a whole level of the food chain will bottom out. new organisms to which these 'toxins' aren't toxic will take the place of the ones that die out.

Corrected.

	02-07-2005 05:26									#105
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ouch, I suppose I should have clicked on the link. it turns the 'toxin' in our oceans is CO2. Oh yes, that'll be the end of the human race for sure.

	02-07-2005 07:46									#106
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quote: Originally posted by Geronimo ouch, I suppose I should have clicked on the link. it turns the 'toxin' in our oceans is CO2. Oh yes, that'll be the end of the human race for sure.

QFT

	02-07-2005 08:20									#107
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A nasty bug spread by unsterilized telephone handsets?

Last edited by Straybow on 02-07-2005 at 08:39