Total capital is constant= manufactured + financial + natural. Use up one type of capital and replace it with another. Completely mined out a trust fund was established for future generations. Must now import almost everything nothing left to trade. Physical flow of resources in maintained, not just value of stock. Fishery levels kept at a level they can replenish themselves. 1976 est. fund to save portion of revenue from oil sands for future generations. 200 workers in 1770 = 1 worker in 1812. Reversing now, natural capital now becoming scarce. Easy to sell-> translates easily make what you have go farther. 10x increase in efficiency of material and energy use is required to keep natural capital from degrading beyond redemption. Mimic nature which uses all resources to their maximum efficiency: service and flow economy. Manufactures can deliver services rather than goods -> maintain ownership of products. Products returned to manufacturer for repair, reuse, and remanufacturing.