Environmentalists and economists frequently suggest that there would be a greater incentive for environmental stewardship if ecosystem services were valued in a manner that reflects the large contribution they have to our economy and society. Assigning a monetary value to a particular service can be very complicated due to issues of scale and the complexity of ecological interactions that make isolating the economic effects of one service difficult. Although challenging, valuation is seen an essential for encouraging conservation. Economists have developed innovative methods that attempt to quantify ecosystem services and the economic benefits of conservation. Check out the EPA Article The Economic Benefits of Protecting Healthy Watersheds