"A plausible scenario for ecosystem collapse... is based on the fact that we currently support 8 billion people on a fossil-intense agricultural system. We have over-leveraged that finite resource to "borrow" millions of years of eco-services (photosynthetic energy) and now host a population that probably never could have existed in ecological equilibrium. Even if fossil fuels were not going away, it seems likely we would see continued erosion of the globe's ability to support this current unsustainable mode. We have already lost about half of the wild animal life in my lifetime: is that halfway to collapse? Take away the fossil fuels, and I imagine over-hunting and rapid deforestation will take an enormous toll on ecosystem health."