Natural capital is the extension of the economic notion of capital (manufactured means of production) to environmental goods and services. A functional definition of capital in general is: "a stock that yields a flow of valuable goods or services into the future". Natural capital is thus the stock of natural ecosystems that yields a flow of valuable ecosystem goods or services into the future. For example, a stock of trees or fish provides a flow of new trees or fish, a flow which can be sustainable indefinetely. Natural capital may also provide services like recycling wastes or water catchment and erosion control. Since the flow of services from ecosystems requires that they function as whole systems, the structure and diversity of the system are important components of natural capital.
- Costanza, Robert et. al. 15 May 1997. "The Value of the World’s Ecosystem Services and Natural Capital." Nature 387: 253-259.
- Costanza, R., Daly, H.E. (1992) Natural capital and sustainable development. Conservation Biology 6, 37-46.
- Daily, Gretchen C., ed. 1997. Nature’s Services. Island Press: Washington, D.C.