Some of the main pressures on sustainable population levels seem to be

- Depletion of topsoil and salination of topsoil
- Depletion of fisheries.
- Reduction/ loss of fossil fuel resources.

I came to this discussion with the idea that the point at which everyone can still eat wild fish regularly is an important bench mark for sustainable population. That is clearly a lower level of population than we have at present. The extent to which our present population and living standard is dependent on oil for food production, preservation and distribution may also be a critical factor.

Reading Jared Diamond's book and other material quoted below suggests that topsoil depletion is far more important than I would have expected.

David Pimentel made the fundamental assumption that all the people in the world would have the current average standard of living in the United States. His estimate called for a substantial reduction in the current human population, indicating that the Earth’s carrying capacity is inadequate to support the current world population at our relatively high standard of living. His numerical estimate was from 1 to 2 billion people. Since current world population is around 6 billion, the obvious question is how we are currently supporting a larger population than Pimentel’s estimate. The answer is that most of the current six billion people have a much lower standard of living than the one assumed by Pimentel in making his projection. Also, supplemental sources of energy, in addition to our daily budget of energy from the sun, are supporting a population that cannot be supported once these (fossil fuel) energy sources are depleted, as is projected to happen before the end of the next century. Any estimate of long term carrying capacity and human numbers must assume the absence of substantial quantities of fossil fuel resources...
1 have been working on the steady-state problem for over a decade now, but considering mainly topsoil as the limiting resource. I now have annotated reviews of the global literature on topsoil loss, forest land degradation, grazing land degradation, irrigated land degradation, and fishery degradation. It has become clear that there is no need to worry about energy— agricultural top soil and those dependent on it will vanish long before the last barrel of liquefied coal is gone...
I am still working on how to apportion global agricultural topsoil losses between croplands and grazing lands, but I suspect the gross rates are not that much different. This would suggest a cropland topsoil loss rate of 50 Gt per year from a maximum inventory (actual plus potential) of at most 7000 Gt, suggesting a lifetime of human civilization of 7000/50 or 140 years. But now consider that once topsoil depths drop below the depth of the root zone (about 6 inches) cropland erosion becomes nearly irreversible and increases rapid. Current optimistic average depths of cropland topsoil are not over 11 inches, and some data say several inches less. So civilization has only about half of its topsoil to spend down before things get really bad. This gives a lifetime for human civilization of about 70 years--barely one human lifetime, and just an eye-blink in terms of human history.

How is this analysis translated into the number of people that the Earth can support sustainably? Assume that net agricultural topsoil loss rates are directly proportional to human population--an assumption that correlates well with global variations in topsoil loss. In order to reduce gross agricultural topsoil loss to the natural rate of agricultural topsoil creation, the Earth's population would need to fall to about a fifth of its present value--perhaps 1.2 billion. Escalation of irrigated land degradation due to salination could drop this figure to well under one billion...

A far more likely steady-state scenario than human population falling to 1.2 billion is that cropland topsoil is largely destroyed, and the Earth becomes a waste land with populations held constant by war, disease, hunger, suicide and genocide. The productivity of sub-soil is not well known, though it is probably not over 10 percent of the productivity of topsoil. Hence the maximum population under the far more realistic steady-state scenario is probably under 10 percent of the maximum population that a not-erosion-limited, topsoil-based civilization can sustain--possibly 0.6 billion...

Fisheries have been neglected in all this. The problem with fisheries is that Man keeps fishing further and further down the oceanic- and fresh-water food chains, and the lower we go the more dispersed fisheries become. At the dispersion value of the open ocean where about 75 percent of oceanic life-creation occurs, fuel costs for fishing boats per ton of fish harvested increases by about a factor of 100 from present-day values. And present-day fishing-boat fuel costs are already a significant portion of the price people now pay for fish. Aquaculture imposes yet another demand on world grain supplies. So although it may provide a positive contribution to protein sources, its contribution to caloric supply is probably negative. And consider that aquaculture usually entails destruction of coastal wetlands, estuaries and mangrove swamps, all of which provide vital breeding grounds for 80-90 percent of ocean fish, and the frequently-diseased fish in ocean aquaculture pens often escape and devastate populations of their wild cousins. So it is not clear that aquaculture provides a net benefit of any kind.

Bruce Sundquist, Carrying Capacity Committee, Allegheny Group, Sierra Club

http://www.population.org.au/affluence/maxpop.htm

Climate change doesn't seem to be factored in.
These limits to population are now being talked of outside the world of population specialists.

Someone dumped some topsoil into a field I can see from my window two years ago. The pile is still sitting there, smooth and rounded by wind and rain, bare and brown, with one or two sad looking weeds growing on it. On only one part, under a tree that some leaves have fallen on, has grass grown.

If the best projections show that our present population won't be sustainable in future, then we need to plan how to manage topsoil and fisheries and our own population levels much better, with the aim of doing it without resource wars and starvation.

The biofuel issue is being blamed by many for removing a lot of land from food production. Because corn/maize was used instead of suger cane as in Brazil it was known that it could not be economical so it required government subsidies. The whole idea was to reduce food production. This was in 1994 and the Senate was tied 50/50 so the vp got to cast the tie breaking vote. Any guesses as to what slug was the vp at the time. BTW does anyone have information on this unusual structure en.wikipedia.org/wiki/Georgia_Guidestones - 39k

You will be well tested going forward as the figures dent your optimism

Good article covering the bases of food needs and how to meet them

Finfacts Link

That Jeffrey Salks charactor was the guy sent to Russia in the early 90's. He did a great job of reducing the population there and Malawi will be delighted to see him.

A few countries have tried 2 child only policies - in Germany and Italy it seems to have happened by individual choice. There are expected to be nasty problems in China over gender balance: one wonders what happened to the girl babies. It is not an easy question but the alternative of escalating population impacts seems to be potentially devastating.

http://worldnetdaily.com/index.php?fa=PAGE.view&pageId=63114
A timely article from today

More reason for America to adopt more liberal immigration policies in order to preserve your society - hispanics are going to be part of your culture and it may be better to integrate them now or integrate with them now rather than struggling later.

If I was a Russian I would be despondent. Buchanan spends a lot of time dwelling on the European area. With regard Ireland I see on the paper that the population will grow to 7 million. Over here people make the economic decision for 2 kids and maybe 3 if a lad gets carried away. What advantage is 2 or 3 million extra people when we are already talking about food shortages. I do not think the happy scenario will play out as hoped for. Why should poor people have 8 kids when most can afford only 2. This all ties in to when the payers will refuse to continue carrying the load and the Welfare State will end. They are tired of corporate/warfare welfare as well. The situation here is about a year ahead of there and I am looking forward to revenue figures from Mr Cowen to see how this will play out.

It is very likely that a large part of the Southern US will want to break off and join Mexico. While this is going on at the bottem, the top level are trying for a North American Union. In the middle we have States bringing in their own immigation laws as they are tired of the federal inaction. Arizona where McCain failed to get 50% in his own state primary and Oklahoma. Even cities and towns are passing their own immigration laws. Some states have groups who want to secede,the latest being Hawaii who want to bring back their king.

Does George Bush pay a lot of tax, youngdan?

He pays plenty but why wouldn't he when he has gotten so wealthy on dubious skills. Anyone on the public purse really pay no taxes because all their money has already being taken from the taxpayer to begin with. Any public servant shoud be just that, a servant to the public, and not a slug living high of the toil of the taxpayer with huge expense accounts.

I don't think the welfare state will end but it might change - people on welfare are required to register for Fás now but I don't really know what happens if they don't take up obligatory training after the time they are given in which to do so - do they lose their social welfare or have to take jobs or what? Education, courses, entertainment etc. are pretty much non-inflationary i.e. they don't draw on finite resources or contribute to wage-spirals as much as other super-valued industries like property construction or supercars. Or travel, perhaps.

Education, exercise and entertainment are economic activities that don't draw as much on finites so I think that policy-makers should encourage these people-areas much more than we are. I regularly hear tutors say "we are waiting for funding for that course" ... why aren't we printing money for these things and taxing other inflationary areas? Tutors and students are there in excess - there is a ready supply of both and usually all they need is a classroom. Is it a heating issue with the building that funding is held back? These activities are non-inflationary and are socially beneficial but are seen as non-productive. What I mean by non-inflationary is that they don't eat into finite resources which we should be avoiding as a society in order to support the people we have.

In short: activities that are not as inflationary in terms of resources should be bolstered and encouraged in any way possible and activities that are inflationary taxed at a higher rate. Travel might get hit and travellers might lose out in that world-view but education and re-defining work should be cornerstones of how we go forward.