Small-scale wars over natural resources.
Massive migrations from regions suffering from famine and lack of water towards areas that still have food stores and water, resulting in friction and potential conflict.
Economic restructuring based on the need to retrench in the face of shrinking petroleum reserves; goods can only be transported so far. On the plus side, exploration of alternative energy sources will eventually expand, once politicians globally wake up.
Increased authoritarianism in much of the globe, with a return to a sort of neo-Feudalism.
Again on the plus side, I see continued technological and medical advances, although the beneficiaries will be a very small wealthy elite.
I hope I’m wrong, but this is some of what I see happening…