Thus, behavior is realized in the organism-environment system. Behavior does not mean movement or interaction of two systems, but action of only one system, reorganization of this system, or change of the relations between its elements. (Järvilehto, 1998, p. 330).But, I don't see how moving to one system rather than two really helps with Järvilehto's problem. If it's a problem that you can't (easily) define a clear boundary between organism and environment taken as systems, then it still seems to be a problem if you can't (easily) define a clear boundary between organism and environment taken as elements. The talk of "reorganization" of the system or "change of the relation between its elements" only seems to mask the problem a little.
Järvilehto, T. (1998). The theory of the organism-environment system: I. Description of the theory. Integrative Psychological and Behavioral Science, 33(4), 321-334.