The evaluation of agricultural land is an area that has received little attention within natural resource economics compared to the evaluation of other ecosystems such as forests or wetlands. A recent attempt by Alexander et al, (1998) (Alexander, A.M., List, J.A.. Margolis, M., d;Arge, R.C., 1998. A method for valuing global ecosystem services. Ecological Economics 27, 161-170) considers one of the functions performed by agricultural land, i.e. agricultural production, and it is based on the mathematical difference between monetary value of output and production expenses. This approach is discussed in relation to the different treatment provided by the market to agricultural and industrial products, to the correctness of the arithmetical procedure, and to the issue of upscaling data from lower to upper levels of the ecosystem hierarchy. Such an approach needs much refinement before the results provided are meaningful. (C) 2000 Elsevier Science B.V. All rights reserved.