The literature on ecological services implies that ecosystems are assets that
produce a flow of beneficial goods and services over time. In this regard,
they are no different from any other asset in an economy, and in principle,
ecosystem services should be valued in a similar manner. That is, regardless
of whether or not there exists a market for the goods and services
produced by ecosystems, their social value must equal the discounted net
present value (NPV) of these flows.