It is done by giving an economic value to an ecosystem or its ecosystem services .
The simplest form of ecosystem valuation for economists is to hold that an ecosystem has a value equivalent to its ecological yield valued as it would be on commodity markets : for the value of water , wood , fish or game , that is purified or nurseried or generated or harboured in that ecosystem . Thus , a price can be put on the natural capital of an ecosystem based on the price of natural resources it yields each year .