IF I understand the previous article sufficiently:

Basically, a diatom makes oxygen by removing the carbon from carbon dioxide and making the carbon a part of it's (exoskeleton?) and then when it dies since the exoskeleton is heavier than water it travels tot he bottom of the fresh water or ocean (there are an incredible amount of different diatom species by the way). So, when the diatom dies it removes the carbon to the bottom of the ocean where thousands to millions of other diatom exoskeletons help compose the freshwater or ocean bottoms worldwide.

My thought is that: "What a disaster it would be to lose all or most diatoms from global warming because not only do they make oxygen they also remove the carbon form carbon dioxide to the bottoms of oceans, rivers and lakes away from living things on land that need to breathe oxygen.

So, If we lose enough diatoms from global warming we will be overrun by even more carbon dioxide and less breathable oxygen worldwide. Because diatoms will no longer be storing the carbon in their exoskeletons and dying and depositing them on the river, lake or ocean floors out of our breathing way (and the breathing way of) all animals, birds, and anything else that breathes air including mankind.

One of the results of all this is people who can survive on lower levels of oxygen will survive while others who can't won't. So, this will be a factor wherever there are lower levels of oxygen in the air ongoing worldwide.

So, likely the people who live at very high altitudes would be like this when they moved to lower altitudes with more oxygen for example.

But, there likely is another factor. At higher altitudes there are less diseases generally and these higher altitude people are vulnerable to the more prevalent diseases at lower especially more tropical altitudes worldwide.

Many many Tibetans died when they had to escape Tibet because of the Chinese invasion of Tibet in the 1950s and died in India of tropical diseases as a direct result. But, many survived and live in places like Dharamshala India at around 6000 feet elevation now.