Economic analyses of nature must somehow define the “environmental commodities” to which values are attached. We articulate principles to guide the choice and interpretation of nonmarket commodities. We describe how complex natural systems can be decomposed consistent with “ecological production theory,” which, like conventional production theory, distinguishes between biophysical inputs, process, and outputs. We argue that a systems approach to the decomposition and presentation of natural commodities can inform and possibly improve the validity of nonmarket environmental valuation studies. We raise concerns about interpretation, usefulness, and accuracy of benefit estimates derived without reference to ecological production theory.