4 ms·

>The notion that this growth is unsustainable is scare mongering. Exponential growth makes this statement as wrong as it can be. It may be scaremongering to sa

by drcube 15y ago

>The notion that this growth is unsustainable is scare mongering. Exponential growth makes this statement as wrong as it can be. It may be scaremongering to say it is unsustainable in the short term, but eventually that growth will have to stop, either due to voluntary decision-making on the part of humans everywhere, or due to a scarcity of resources. Or in fact both, given that the scarcity of resources will cause people to decide on reproducing less. Growth in general is simply not sustainable in the long term. Isaac Asimov once estimated that at "today's" rate of growth (circa 1970), Earth would become a ball of human flesh expanding at the speed of light by 5000AD. Of course its a ridiculous prediction, but it illustrates that between now and then, something must change. Look at this chart: http://en.wikibooks.org/wiki/File:2nd_Order_Damping_Ratios.svg http://en.wikibooks.org/wiki/File:2nd_Order_Damping_Ratios.s... Assuming 1 here refers to the maximum "sustainable" population, we'll either oscillate around it, overshoot and come back, or asymptotically approach zero percent growth. There is no such thing as a system with no feedback, which is allowed to grow without bound. It may seem like there are no constraints currently, but they're out there, and eventually we'll hit them.

a-priori 15y ago
The world population is not experiencing exponential growth. It's experiencing logistical growth (i.e, following a logistical function rather than an exponential function). We've just been seeing the first half of the curve, which does approximate exponential growth. But we're starting to see it turn around. In the most developed countries, fertility has dropped to replacement or lower. As the remaining countries develop, their fertility rates are also dropping. It's reasonable to extrapolate from this that at some point in the future, the global fertility rate will be at or below replacement. The constraints are microeconomic. It's expensive to raise children, especially when you factor in opportunity costs (this part is key to why world population won't stabilize at starvation levels). When you give people birth control, people seem to make a rational economic decision about how many children to have. That provides the feedback mechanism you mentioned.
- beloch 15y ago
  The developing world has birth control but, in large parts of it (e.g. most of africa), most people aren't using it. This is for economic reasons. In these economies children are your pension fund. There's no RRSP funds or old age security payments. Just children who (hopefully) look after you in your old age. If you have only one or two you will either be an unreasonable burden upon them or simply be abandoned to starve. The economic support system for seniors in the developed world is currently under a lot of strain too. In countries where pension funds are funded from current taxes the baby-boomer retirement is going to be a tremendous drain on society. The baby-boomer generation should have tucked away a nice huge fund to pay them in retirement as well as support the greater demand on the medical system. Instead, they racked up huge amounts of public debt. Massive amounts of immigration and raising the retirement age have been the stop-gap measure of choice so far, but the developed world's support for senior citizens could easily revert to that of the developing world's without much warning! So, yes, children are expensive, but for most of history and in large parts of the world today they are a necessary investment for retirement. In only the developed world of the past century have financial pressures favored fewer children, and that could easily change.
  - DilipJ 15y ago
    fertility rates are dropping worldwide. At some point in the next 30 years, it is expected to fall below replacement level. Check out this graph comparing fertility rates. China and Iran (!) now have fertility rates below that of the U.S. http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_dyn_tfrt_in&idim=country:USA&dl=en&hl=en&q=fertility+rate#ctype=l&strail=false&bcs=d&nselm=h&met_y=sp_dyn_tfrt_in&scale_y=lin&ind_y=false&rdim=region&idim=country:USA:CHN:IRN&ifdim=region&tdim=true&hl=en&dl=en http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&#...
    - 6ren 15y ago
      Curiously, rates for Italy and Germany are separated from other developed countries by about .5% http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_dyn_tfrt_in&idim=country:USA&dl=en&hl=en&q=fertility+ http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&#...
3pt14159 15y ago
That makes no sense though. Assuming exponential growth, then it wouldn't grow as a sphere going at the speed of light. The derivative would be a quadratic, not a exponential curve. So if anything that would only approximate the growth for a couple days, at which point exponential would take over. But this presupposes that the humans started on the earth at 5000 AD, where in reality we will have almost certainly taken over venus (aside: Venus is a much more likely target for human colonization than Mars) and probably have several space station states which could easily move at near the speed of light away from the earth.

by drcube 15y ago

a-priori 15y ago

The world population is not experiencing exponential growth. It's experiencing logistical growth (i.e, following a logistical function rather than an exponential function). We've just been seeing the first half of the curve, which does approximate exponential growth. But we're starting to see it turn around. In the most developed countries, fertility has dropped to replacement or lower. As the remaining countries develop, their fertility rates are also dropping. It's reasonable to extrapolate from this that at some point in the future, the global fertility rate will be at or below replacement. The constraints are microeconomic. It's expensive to raise children, especially when you factor in opportunity costs (this part is key to why world population won't stabilize at starvation levels). When you give people birth control, people seem to make a rational economic decision about how many children to have. That provides the feedback mechanism you mentioned.

beloch 15y ago
The developing world has birth control but, in large parts of it (e.g. most of africa), most people aren't using it. This is for economic reasons. In these economies children are your pension fund. There's no RRSP funds or old age security payments. Just children who (hopefully) look after you in your old age. If you have only one or two you will either be an unreasonable burden upon them or simply be abandoned to starve. The economic support system for seniors in the developed world is currently under a lot of strain too. In countries where pension funds are funded from current taxes the baby-boomer retirement is going to be a tremendous drain on society. The baby-boomer generation should have tucked away a nice huge fund to pay them in retirement as well as support the greater demand on the medical system. Instead, they racked up huge amounts of public debt. Massive amounts of immigration and raising the retirement age have been the stop-gap measure of choice so far, but the developed world's support for senior citizens could easily revert to that of the developing world's without much warning! So, yes, children are expensive, but for most of history and in large parts of the world today they are a necessary investment for retirement. In only the developed world of the past century have financial pressures favored fewer children, and that could easily change.
- DilipJ 15y ago
  fertility rates are dropping worldwide. At some point in the next 30 years, it is expected to fall below replacement level. Check out this graph comparing fertility rates. China and Iran (!) now have fertility rates below that of the U.S. http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_dyn_tfrt_in&idim=country:USA&dl=en&hl=en&q=fertility+rate#ctype=l&strail=false&bcs=d&nselm=h&met_y=sp_dyn_tfrt_in&scale_y=lin&ind_y=false&rdim=region&idim=country:USA:CHN:IRN&ifdim=region&tdim=true&hl=en&dl=en http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&#...
  - 6ren 15y ago
    Curiously, rates for Italy and Germany are separated from other developed countries by about .5% http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&met_y=sp_dyn_tfrt_in&idim=country:USA&dl=en&hl=en&q=fertility+ http://www.google.com/publicdata/explore?ds=d5bncppjof8f9_&#...

3pt14159 15y ago

That makes no sense though. Assuming exponential growth, then it wouldn't grow as a sphere going at the speed of light. The derivative would be a quadratic, not a exponential curve. So if anything that would only approximate the growth for a couple days, at which point exponential would take over. But this presupposes that the humans started on the earth at 5000 AD, where in reality we will have almost certainly taken over venus (aside: Venus is a much more likely target for human colonization than Mars) and probably have several space station states which could easily move at near the speed of light away from the earth.