Valuing pollination services to agriculture

Crop pollination by animal pollinators is an important ecosystem service for which there is no generally accepted valuation method. Here, we show that two existing valuation methods, previously thought to be unrelated, are each a special case of a more general equation. We then present a new method, termed attributable net income, for valuing insect pollination of crops. The attributable net income method improves upon previous methods in three ways: (1) it subtracts the cost of inputs to crop production from the value of pollination, thereby not attributing the value of these inputs to pollinators; (2) it values only the pollination that would be utilized by the crop plant for fruit production, thereby not valuing pollen deposited in excess of the plants' requirements; and (3) it can attribute value separately to different pollinator taxa, for example to native vs. managed pollinators. We demonstrate all three methods using a data set on watermelon pollination by native bees and honey bees in New Jersey and Pennsylvania, USA. We discuss the reasons why different methods produce disparate values, and why the attributable net income method most accurately reflects the actual ecosystem service that is being valued, marketable fruit production. (C) 2011 Elsevier B.V. All rights reserved.