MIT has created a model called the limits to growth which calculates that civilization will collapse by 2040 if it keeps going business as usual. But how accurate is this model and what will cause this 'collapse'?
Further concentration of wealth in the one half of one percent of the population is a big reason. Indeed, the continued acquisition of assets by private equity firms globally is bothersome.
Access to water and resources. Haber-Bosch managed the issue of yield. The trouble is, we have a groundwater issue brewing. We can toss it on the pile of out of sight/out of mind though. I'm talking about the depletion of GROUNDWATER resources across America, including, the Central and Midwest portions. Our agriculture is using up the resources faster than the aquifers can recharge. link, link, link
Simply, reliers upon overbuilt urbs in waterless areas are going to go through some things, just as those located on coastlines and floodplains with all kinds of water. As to agriculture, the problem is in areas with extensive crop irrigation.