What do human beings take from planet Earth? Everything they can. What do they give back in return? Garbage, sewage, concrete, carbon dioxide, and plastic. 7.7 billion homo sapiens live in the world. That number is on an incline rising upward. That is the main demographic problem.
All resources are finite. Not just fossil fuels. There is a second incline going upward. All of the formerly third world nations are busy trying to join the prosperous first world countries. They want to become more like us. Concurrent with the rise in the standard of living in dozens of nations is the diminishing supply of trees, arable land, fresh water, soil with no chemical contamination, air and water which is not polluted in any way, and a big increase in people disaffected in many ways and in various places.
The world is infinitely complex. Demographic problems exist side by side with problems, or shortcomings in human nature. Many people lack the ability to envision long range problems. Climate change looms large in the future, and it demands a great deal of foresight and long range planning to deal with.
The daunting challenges innate in adapting to ongoing, and growing changes in the future may lead to peril(how many decades ahead?) for our civilization.
Deuel Woodward in Chula Vista.