The systems on which we rely for our financial transactions, food, fuel and livelihoods are so inter-dependent that they are better regarded as facets of a single global system. Maintaining and operating this global system requires a lot of energy and, because the fixed costs of operating it are high, it is only cost-effective if it is run at near full capacity. As a result, if its throughput falls because less energy is available, it does not contract in a gentle, controllable manner. Instead it is subject to catastrophic collapse.
Read the whole post, article really, at Fleeing Vesuvius, On the cusp of collapse: complexity, energy, and the globalised economy by David Korowicz
I would have subtitled the article, "Hanging by a thread." Civilization really does hang by just a few threads, and if any one of them is cut or breaks, the whole house of cards comes crashing down. This is systemic risk in the extreme.
Every engineer knows that redundancy is required in fragile system to ensure that if any key components fail, there is an adequate backup. That's why cars have emergency breaks, for example. There is little redundancy built into the modern global economy, whose purpose is to materially provision humanity, and few buffers are available for vital resources.