This particular quote has been attributed to a lot of different people, everyone from Muhammad to Martin Luther King, but, in some variation, reads as:

"Even if you knew the world would end tomorrow, plant a tree."

I think fear of everything ending is an elaboration of an innate human fear. Certainly there is evidence for that as most of the religions provide for some end to humans in some fashion. At least our time on this earth.

It's likely an elaboration of the fear of our own mortality writ large.

Not saying it is without merit. Everything, in fact, could end tomorrow.

So I guess the question becomes "what kind of tree to plant..."