The threat is in the form of increasing global warming which results in climate change. Generating Bitcoin requires a capable computer to solve complex mathematical puzzles and high electricity consumption. so that some countries prohibit mining for several other reasons such as in China and Iran some time ago. if so will bitacoin and others be able to run forever or is this just an excuse to change the green field to red..

Exactly,  there are no such mining farms in the world right now as we have many factories scattered all over the world with the constant population they generate on a daily basis both on air and sea, chemical spills and disposal of toxic waste into the atmosphere possess a more dangerous situation to the human health, why nobody is paying attention to that,

some of this factories have been running for years long before btc and btc mining will ever become a thing,  humans has always endure this pollution and the environment threat,  it seem very easy to shift the blame of global warming to btc mining rather than the obvious.

Bitcoin Cultist ....

The heat from your computer is not wasted if you need to heat your home.  If you're using electric heat where you live, then your computer's heat isn't a waste.  It's equal cost if you generate the heat with your computer.

If you have other cheaper heating than electric, then the waste is only the difference in cost.

If it's summer and you're using A/C, then it's twice.

Bitcoin generation should end up where it's cheapest.  Maybe that will be in cold climates where there's electric heat, where it would be essentially free.

It's the same situation as gold and gold mining.  The marginal cost of gold mining tends to stay near the price of gold.  Gold mining is a waste, but that waste is far less than the utility of having gold available as a medium of exchange.

I think the case will be the same for Bitcoin.  The utility of the exchanges made possible by Bitcoin will far exceed the cost of electricity used.  Therefore, not having Bitcoin would be the net waste.

Each node's influence on the network is proportional to its CPU power.  The only way to show the network how much CPU power you have is to actually use it.

If there's something else each person has a finite amount of that we could count for one-person-one-vote, I can't think of it.  IP addresses... much easier to get lots of them than CPUs.

I suppose it might be possible to measure CPU power at certain times.  For instance, if the CPU power challenge was only run for an average of 1 minute every 10 minutes.  You could still prove your total power at given times without running it all the time.  I'm not sure how that could be implemented though.  There's no way for a node that wasn't present at the time to know that a past chain was actually generated in a duty cycle with 9 minute breaks, not back to back.

Proof-of-work has the nice property that it can be relayed through untrusted middlemen.  We don't have to worry about a chain of custody of communication.  It doesn't matter who tells you a longest chain, the proof-of-work speaks for itself.