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Back home, the Tibetan Plateau averages 4,950 meters above sea level with its highest point being Mount Everest, 8,848 meters--29,029 feet--above sea level. At such heights, problems are resulted as listed:

  • The air becomes cold, dry and most importantly, thin.
  • The Himalayas are so tall that they bar off the monsoon winds from reaching Tibet, turning the plateau dry enough for grasslands to dominate it.
  • The most serious problem is that a thinner air means greater vulnerability to ultraviolet radiation.

Fortunately, complex life--plants and animals--find ways to deal with these problems. As a result, Tibet is alive with wolves, bears, snow leopards, yaks, asses, antelope, cranes, vultures, hawks, geese and even snakes. Of course, the one Tibetan that stands out above the rest is a species aptly called the "high-altitude jumping spider".

Now in this alternate Earth, Tibet is taller--6,000 meters above sea level on average, with the tallest point being 10,211 meters--33,500 feet--above sea level. At such heights, the three problems listed above become even more pronounced, which raises the pressure in regards to residing there. Can plant and animal life still flourish in this taller Tibet, or are our Tibetans currently living at the top of their limits?

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    $\begingroup$ Why the close votes? Rounding issues aside, this is a good question. $\endgroup$ – o.m. Jul 7 '17 at 4:07
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    $\begingroup$ I think I read somewhere that mount Everest is close to the maximum theoretical height for a mountain on Earth. If my memory is correct than your assumption that on an alternate Earth the alternate Everest is 10 km high is wrong. $\endgroup$ – L.Dutch Jul 7 '17 at 5:10
  • $\begingroup$ @L.Dutch If you are correct about he maximum theoretical height for mountains this alternate Everest is only two kilometres above the limit. It's arithmetic that tells me so. $\endgroup$ – a4android Jul 7 '17 at 8:59
  • $\begingroup$ I don't have time for a full answer but yes, it's possible : link.springer.com/article/10.1007/s00248-016-0779-8 $\endgroup$ – Vincent Jul 8 '17 at 19:30
  • $\begingroup$ But I need to correct you on something, the monsoon does affect Eastern Tibet, coming from the Pacific ocean. Lhasa has a wet summer. $\endgroup$ – Vincent Jul 8 '17 at 19:31
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Plant and animal life on the plateaus: Yes. The air pressure will be roughly 15% less than in the real world. I have no doubt that plant and animal life in general will survive.

  • The height of the tree line depends on the wind in addition to pressure. Above the treeline there are lesser plants.
  • Birds can reach well over 8000 m.

Human life on the plateaus: At least briefly. The lethal altitude seems to be between 7000 to 8000 m, except for exceptional individuals and brief periods.

Mountains vs. Plateaus. In the real world, altitudes above 6000 m combine the effects of low pressure with a mountain slope. This complicates finding shelter, areas to grow food crops, etc. Your fictional plateau should be more hospitable than a real-world mountain at 6000 m.

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  • $\begingroup$ How do you mean "in general"? $\endgroup$ – JohnWDailey Jul 7 '17 at 18:55
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    $\begingroup$ @JohnWDailey, some species will be lost. The ecology won't be the plateaus as we know them.But some life will remain. It is remarkably hard to eradicate. $\endgroup$ – o.m. Jul 8 '17 at 6:30
  • $\begingroup$ Who said anything about "losing" species? $\endgroup$ – JohnWDailey Jul 8 '17 at 12:25
  • $\begingroup$ @JohnWDailey, I did. By moving the plateau up, the ecology will change. $\endgroup$ – o.m. Jul 8 '17 at 14:11
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It will be tough

I am not a doctor or an expert on the topic, but I cannot find any sources for permanent acclimatizing by humans above 5500 meters.

La Rinconada, in Peru, is the highest known permanent settlement, and it's only at 5100 meters.

Military studies show no adaptation and continuous degradation of functionality above 5500-6000 meters, with the death zone starting around 7000. There is a good source from the US Army here. Admittedly, this is under the stress of military opeartions, but about 20% of military personnel seems to develop HAPE (potentially fatal bleeding in the lungs) operating over 5000 meters.

Above 6500 meters, sleeping becomes very difficult, digesting food is near-impossible, and the risk of HAPE increases greatly.

As far as vegetation goes, you're either in the nival (permanent snow) zone or in alpine desert territory. You're unlikely to get anything beyond lichen and maybe a few scattered grasses. It'll be mostly gravelly desert. Whether it will be ice or desert is determined by latitude and the prevailing winds. But to put things in perspective, even in a tropical context with wet winds you're likely in a alpine desert situation above 4500 meters or so. Obviously in temperate and boreal mountains the permanent ice cover will be much lower.

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At 6000m, you will have a problem.

In Tibet, this altitude is dominated by snow zone. While people and animals can visit it, there is no vegetation, and no open ground agriculture is possible. Life on such plateau will occupy only valleys with lower elevation.

P.S. In case of low precipitation, the plateau would have more alpine deserts and less snow, however it's still the problem to have any noticeable vegetation.

Zonation case study

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  • $\begingroup$ How can you have snow without the monsoon? $\endgroup$ – JohnWDailey Jul 7 '17 at 18:54
  • $\begingroup$ @JohnWDailey, well, there is not that much snow in Tibet, but even in low snowfall, it gets accumulated over the time. Let me add a little clarification. $\endgroup$ – Alexander Jul 7 '17 at 18:59
  • $\begingroup$ Can lichen, a symbiotic relationship between photosynthetic algae and extremophilic fungus, fare better? $\endgroup$ – JohnWDailey Jul 7 '17 at 19:19
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    $\begingroup$ Lichen can do better, but they are very slow growing (in fact, any conceivable vegetation in that zone would be slow growing) and can't form the base of a diverse ecosystem. $\endgroup$ – Alexander Jul 7 '17 at 19:39

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