Are you an Optimist or Pessimist?

[Darwinsbulldog]

Originally Posted by The Irreverent Mr Black

I am indeterminate as to whether these comments have the best or worst of my interests at heart.

Always the best, Mr. B.

[Jaar-Gilon]

Originally Posted by Atheos

human extinction on this planet at least is inevitable imo, it is simply a matter of time, might be tomorrow, might be when the sun finally goes supernova, or at any stage in between, extinction level events have happened numerous times in the past, we are not excluded from the probability. pessimist ftw

Our sun will never go supernova, it's not massive enough. It is destined to become a red giant and then finally a white dwarf.

[Sieveboy]

Originally Posted by Jaar-Gilon

Our sun will never go supernova, it's not massive enough. It is destined to become a red giant and then finally a white dwarf.

Yup, a gamma ray burst or rogue asteroid is a far more likely cosmic killer.

[bruce1937]

I am a realistic pessimist, the human race will go the way of dinosaurs at some stage, religion has the potential to bring us to our knees but it will take a cosmic event to finish us off.

[Centauri]

Originally Posted by bruce1937

I am a realistic pessimist, the human race will go the way of dinosaurs at some stage, religion has the potential to bring us to our knees but it will take a cosmic event to finish us off.

Well said, I like it.

[owheelj]

I'm an optimist. It seems a bit silly to call yourself a pessimist because you recognise that Earth will become uninhabitable in a few billion years, and I think we can be pretty confident that it will take a more significant catastrophe than a meteorite of the size that killed the dinosaurs to wipe us out (and of course, our ancestors survived that one).

[Darwinsbulldog]

Originally Posted by owheelj

I'm an optimist. It seems a bit silly to call yourself a pessimist because you recognise that Earth will become uninhabitable in a few billion years, and I think we can be pretty confident that it will take a more significant catastrophe than a meteorite of the size that killed the dinosaurs to wipe us out (and of course, our ancestors survived that one).

Survival of ancestors does not imply survival of offspring. Only the reverse is true. If you are alive, it means all your direct ancestors survived long enough to reproduce. Even the most optomistic assesment of a nuclear winter scenario makes human survival problematic. The collapse of food webs, caused by ash clouds from nukes or impacting meteorites shuts down photosynthesis. That means most species are wiped out. Of the animals, it is extremely rare for large ones [like us]to survive. If the photosysnthesis by plants is not possible for years or decades, then small animals only can survive if they can find edible roots and seeds.

Nor is our science or technology likely to help us all that much. If most people die, then we will lose, or have a vastly reduced, skill set. Modern urban skill sets do not translate well into bush survival skills. Most medical support will collapse, from fatalities in medical people, loss of medical equipment and drugs, and vast imbalance between medical supply and demand.
Perhaps military stocks of food, water etc, may help. But one can reckon on the likely collapse of government, major panic, and perhaps anarchy and war between those who survive on what meagre resources are left. Given even these few observations of the top of my head, I don't see how human survival is anywhere near a done deal. I am almost certain I have posted at least one paper in the science sub-forum that says ecosystem recovery can take as much as 10 million years. So many species that survive the initial disaster can fade out later due to missing relationships. eg Plants losing pollinator species, and thus having to fall back [if they can] on dispersal by wind and water. Stuff like that.

A few quick refs:-

Coxall, H. K., S. D'Hondt, et al. (2006). "Pelagic evolution and environmental recovery after the Cretaceous-Paleogene mass extinction." Geology 34(4): 297-300.
D'Hondt, S., P. Donaghay, et al. (1998). "Organic Carbon Fluxes and Ecological Recovery from the Cretaceous-Tertiary Mass Extinction." Science 282(5387): 276-279.
Jablonski, D. (2002). "Survival without recovery after mass extinctions." Proceedings of the National Academy of Sciences 99(12): 8139-8144.
Payne, J. L., D. J. Lehrmann, et al. (2004). "Large Perturbations of the Carbon Cycle During Recovery from the End-Permian Extinction." Science 305(5683): 506-509.
Sahney, S. and M. J. Benton (2008). "Recovery from the most profound mass extinction of all time." Proceedings of the Royal Society B: Biological Sciences 275(1636): 759-765.
Solé, R. V., J. M. Montoya, et al. (2002). "Recovery after mass extinction: evolutionary assembly in large–scale biosphere dynamics." Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 357(1421): 697-707.
The bolded refs are fully downloadable.

[owheelj]

Sure, I'm not denying it would be bad. But I think the probability of it wiping out humanity would be small. For starters, wind powered hydroponic food could still be grown, and many plants, including food plants, grow with limited light anyway. Clearly the Dinosaur asteroid allowed enough light to get through the atmosphere that a wide variety of plants and animals survived. In such a situation, I think we can be confident that there would be humans alive, adapting to the new conditions. The fact that we're such generalists makes it far more difficult for us to go extinct than the average organism. When you look, for example, at the Australian threatened species list, nearly everything on it has always had a narrow niche, while when you look at the native and introduced plants and animals that are a prospering in Australia - like us, they're generalists.

It's also worth noting that ash and those kinds of aerosols have very short atmospheric half lives. Although a massive event like a meteor puts up so much ash that some amount is in the atmosphere for years, it almost immediately starts settling out, so things start getting better almost immediately. Humans now live almost across the entire planet, it's easy to imagine that some populations would survive a massive catastrophe, unless it wiped out all multicellular life. We also have to recognise that humans aren't the same as other animals, particularly in our abilities to think, and so if our normal way of life was destroyed, unlike many organisms, we'd be capable of figuring out a way around it, if a way existed. Many of the endangered animals in Australia would probably be fine if they would just change their behaviour. We can change ours.

[Darwinsbulldog]

Originally Posted by owheelj

Sure, I'm not denying it would be bad. But I think the probability of it wiping out humanity would be small. For starters, wind powered hydroponic food could still be grown, and many plants, including food plants, grow with limited light anyway. Clearly the Dinosaur asteroid allowed enough light to get through the atmosphere that a wide variety of plants and animals survived. In such a situation, I think we can be confident that there would be humans alive, adapting to the new conditions. The fact that we're such generalists makes it far more difficult for us to go extinct than the average organism. When you look, for example, at the Australian threatened species list, nearly everything on it has always had a narrow niche, while when you look at the native and introduced plants and animals that are a prospering in Australia - like us, they're generalists.

It's also worth noting that ash and those kinds of aerosols have very short atmospheric half lives. Although a massive event like a meteor puts up so much ash that some amount is in the atmosphere for years, it almost immediately starts settling out, so things start getting better almost immediately. Humans now live almost across the entire planet, it's easy to imagine that some populations would survive a massive catastrophe, unless it wiped out all multicellular life. We also have to recognise that humans aren't the same as other animals, particularly in our abilities to think, and so if our normal way of life was destroyed, unlike many organisms, we'd be capable of figuring out a way around it, if a way existed. Many of the endangered animals in Australia would probably be fine if they would just change their behaviour. We can change ours.

Very few species of plants can survive total photosynthetic shutdown, even for limited periods of time. Plant survival mainly depends on surviving seed stocks, and root stocks of tuber plants and so on. And as I implied, the survival of small animals would depend on them finding roots and seed to eat, and only a very limited number of small predators could be supported by these small herbivores.
As we are at the top of most land [and some sea] food chains, our large mass would mean only very small numbers of humans would gain a living from this, despite our omnivorous nature.
Our main assets are our intelligence, social system and accumulated knowledge. As I said, it is probable that our social systems would be massively disrupted by the many deaths. Infrastructure like hydroponics still requires energy, and given low light conditions, we would have to augment that artificially. Given our rate of depletion or fossil fuel inventories, we may not find sufficient and easily obtainable remaining stocks of fossil fuels to power much in the way of anything, never mind hydroponic farms. If most miners or oilmen are dead, who gets the fuel? Ditto with nuclear power generation. A meteriod impact the size of a dino-killer would knock out many power plants of all types from winds, floods, earthtquakes tsunamis and widespread fires. This would include damage to wind, solar, dams, etc, etc.

I am not saying it would be impossible for humans to survive, just very unlikly.

[owheelj]

The FAO estimates that it takes a 6x6m plot of arable land to grow enough food to sustain 1 person for a year (1), but far less for hydroponic systems. Within walking distance of my house is 4 wind turbines that would generate enough electricity to power a small hydroponic system (the only necessary energy input is for lighting - water and nutrients can be provided by hand). Wind turbines are relatively easy to build, and can be done so with effectively junk(2). This is not an option for everybody, and no doubt millions would die, but communities near wind farms or with technical minded people would be able to go with such options and survive.

The atmospheric half life of stratospheric volcanic ash is ~2 years (3). So two years after the meteorite hit the effect of the ash cloud would probably have halved. There's also the question of air currents and the fact that the ash would almost certainly not be equally distributed. For example places like Hawaii and the West Coast of Tasmania are in places where air pollution from cities takes years to reach(4). It's probable that the concentration of ash over places like Hawaii and Tasmania would be significantly less than at continents where a continental effect would cause aerosols to concentrate (5). With lower amounts of ash, and a short atmospheric half life of ash, people in these places would only need to survive for a few years before they'd be able to grow vegetables outside themselves.

Finally, although the majority of species of plants do need high amounts of light (mainly because species diversity correlates with latitude), many plants, especially alpine plants and saltmarsh plants require far less (6). A number of plants on Mt Wellington (including but not limited to the reference) have been found to barely photosynthesise during winter at all (7). While many places around the world would become uninhabitable, some places would still have some amount of primary productivity, and a small number of humans would be able to survive off this for the few years it would take before the amount of solar radiation was high enough for shade tolerant vegetables to grow.

Finally I note that the vast majority of electricity generation in the world is not reliant on the sun, so it's easily conceivable that a few communities out of all the world would manage to keep their electricity running and redistribute the majority of it towards growing food hydroponically. You only need to maintain a population of a few thousand to give us a 90%+ chance of surviving into the indefinite future (8).


1. The Ultimate Resource 2 by Julian Simon 1996, Princeton University Press, pp 100-101.

2. http://www.ted.com/talks/william_kam..._the_wind.html

3. Assessment of the atmospheric impact of volcanic eruptions by Sigurdsson, H. 1988, published in Abstracts Presented to the Topical Conference on Global Catastrophes in Earth History: An Interdisciplinary Conference on Impacts, Volcanism, and Mass Mortality. p. 177

4. http://kurungabaa.net/2011/10/02/cap...e-air-quality/

5. The Weather and Climate of Australia (2nd Edition) by A Sturman and N Tapper 1997, published by Oxford University Press. pp. 206-241.

6. Plant Physiology (4th ed) by L Taiz and E Zeiger 2006, published by Sinauer Associates. pp. 152-153, 208-209.

7. Reflectance and phenolics of green and glaucous leaves of Eucalyptus urnigera by D.C. Close et al, (2007). Australian Journal of Botany 55(5), pp. 561-567.

8. http://en.wikipedia.org/wiki/Minimum_viable_population