Unelaborated nihilism is the most useless of all arguments. If we were to take your point to extreme, we wouldn't get out of bed because everything will disappear one day. So, for a claim like this to contribute something to the conversation, one needs to explain why uselessness of this thing overpowers usefulness of other things.

Across the permanence of time all things will but that doesn’t mean we shouldn’t enjoy them whilst they’re here.

So will your comment, with time. And this reply.

Why not spiral down a nihilistic pit and write off our brief existences?

...and come back again, only to disappear once more whereupon they reform in the next cycle. This has happened many times already and it will continue on its way until the sun heats up the atmosphere enough to boil off all water/Iceland succumbs to some massive volcanic eruption/etc.

Realise that according to the prophesies of doom you are quoting you would have been dead many times over, many years ago. Seeing as how you're still around to tell us those glaciers will meet an untimely end those prophecies - and with that your claim - do not carry the weight they are often given.