From the previous chapter, it should be apparent that choice of variables to use in a monitoring program is a critical decision and not one to make arbitrarily or hastily. However, many biomonitoring texts (e.g. Davis & Simon 1995; Karr & Chu 1999; Rosenberg & Resh 1993) focus upon only particular taxonomic groups or particular kinds of variables. Specific biomonitoring studies are spread over many different journals, from those specializing in particular taxa to ones on whole communities, and from those publishing mainly in areas of basic ecology to those directed specifically at applied ecology or environmental management. It is difficult for any individual to keep track of all of this literature, and researchers can often be unaware of developments outside their immediate field of expertise.

Here, we summarize briefly the characteristics of useful variables. Although much of this material is discussed in other chapters (chapters 6, 9 and 11), we summarize it here simply to emphasize that useful monitoring variables are not necessarily associated with particular taxonomic groups and that researchers are advised to look widely across the taxonomic and ecological range. From chapter 9, it should be clear that dogmatic advice about which taxa should be monitored should be avoided. Although this may disappoint those who prefer simple recipes, choice of response variables requires measured consideration of a number of attributes.