While teaching at Milton College decades ago, I invited Analog editor Ben Bova to give a talk. His main thesis was that for humanity to survive long term, we must expand beyond the earth. Planet earth is "humanity's cradle" but we must grow up and learn to live outside our cradle.
If we are to remain limited by c (speed of light), then most of the Universe, and even of our galaxy, will be out of reach. But our solar system has plenty of space and resources for us. Since most of the other planets are unsuitable, we must build large space stations that can grow food and become "cities in space". Instead of lifting all that building material "up" from the earth, we can drop it "down" from the asteroid belt.
At that time, the 1970's, the problems were mostly the population explosion, and running out of resources, and space to grow food. This was before Climate Change and Global Warming became concerns.