In 1988 Kurt Vonnegut wrote a short letter of advice to the people of 2088. The full letter, which is short, is here. An excerpt:

Our century hasn’t been as free with words of wisdom as some others, I think, because we were the first to get reliable information about the human situation: how many of us there were, how much food we could raise or gather, how fast we were reproducing, what made us sick, what made us die, how much damage we were doing to the air and water and topsoil on which most life forms depended, how violent and heartless nature can be, and on and on. Who could wax wise with so much bad news pouring in?

For me, the most paralyzing news was that Nature was no conservationist. It needed no help from us in taking the planet apart and putting it back together some different way, not necessarily improving it from the viewpoint of living things. It set fire to forests with lightning bolts. It paved vast tracts of arable land with lava, which could no more support life than big-city parking lots. It had in the past sent glaciers down from the North Pole to grind up major portions of Asia, Europe, and North America. Nor was there any reason to think that it wouldn’t do that again someday. At this very moment it is turning African farms to deserts, and can be expected to heave up tidal waves or shower down white-hot boulders from outer space at any time. It has not only exterminated exquisitely evolved species in a twinkling, but drained oceans and drowned continents as well. If people think Nature is their friend, then they sure don’t need an enemy.

If I can summarize the sentiment, what he found depressing is that we have the knowledge and ability to understand what is going on and do something about it, and yet as a civilization and species we are failing to do anything.