ABSTRACT
A model is an abstract of reality. It can be regarded either as a formal description of the essential elements of a problem, or as a description of the systemof-interest. Models can be classified into physical versus abstract, dynamic versus static, empirical versus mechanistic, deterministic versus stochastic, and simulational versus analytical. A system is an interlocking complex of processes characterized by many reciprocal cause-effect pathways (Watt, 1966; Swannack and Grant, 2008). In relation to physical science, a system is an organized collection of interrelated physical components characterized by a boundary and by functional unity (Grant et al., 1997). Ecological modeling on a global level is the process of simulating and analyzing the ecosystem-of-interest in terms of the principles of global ecology, which are absolutely essential in trying to understand the environmental problems affecting the world. For example, the simulation and analysis of global ecosystem services must calculate climate, soil, landform, hydrology, energy resources, and human impacts.
