Christianity, Platonism, and various political movements that aim toward a distant utopian future, and any other philosophy that devalues human life and the world around us (and any philosophy that devalues the world around us by privileging some other or future world necessarily devalues human life), Nietzsche tells us it is also a threat for humanity’s future. This warning can also be taken as a polemic against 19th and 20th century scientism.
I’m not interested in arguing whether this is actually what Nietzsche actually said/meant. It more or less sums up the problem to me.
Here’s a conversation at World Changing about optimism and pessimism (which also links to this sort of “portal article” about the problems we face and the rate of change). I consider myself a skeptical optimist. I believe we can overcome our current social and environmental problems. But it will take work and adaptation.