Ecological Systems Thinking
To understand systems thinking, we should first align on what a system is. A system is a set of interrelated, interactive, and interdependent cofpomponents. For example, an area of sagebrush steppe is a system of plants, soil, animals, water, solar radiation, and so on (figure 4.1), all of which interact with one another in one or more ways.
Systems comprise various components, interactions, and controls. Systems have purpose. A good way to think about the purpose of an ecological system is to describe it as an ecosystem providing goods and services. Understanding the fundamental purposes (note plural—more than one purpose) of ecological systems is critical for land use and management.
For a system to function optimally, all components must be present and functional. This characteristic of a system relates to biodiversity and redundancy. When a component, interaction, or control is missing from a system, a ripple effect may be put in motion. For example, when wolves (Canis lupus) were removed from Yellowstone, predation pressure on elk (Cervus canadensis) dropped dramatically, and elk populations increased. Elk prefer to browse on woody species, and as a result of the increased elk population, birch species in riparian areas were overbrowsed; riparian areas, stream channels, and ecosystems degraded. The reintroduction of wolves to the Yellowstone system illustrates the last characteristic of a system: through interactions, controls, and feedback, a system is capable of maintaining stability.
Systems thinking considers the cohesive whole: how all the components relate to and influence one another. Systems thinking reveals how changes in one component, control, or interaction impact other components, controls, or interactions. Understanding these dynamics gives us multidimensional insight into a system. For example, figure 4.2 illustrates many basic connections along the banks of the Green River outside of Moab, Utah.
It is important to remember that ecological systems are highly dynamic and ever-changing. Thinking in systems enables one to better understand system dynamisms and thus to anticipate trajectories of change due to land use, management, or disturbance. What we most readily notice about systems are events, such as a fire disturbance, grazing, or the surface of a landscape view, and these events generally drive our management decisions. What we need to see and understand to make better, holistic, management decisions are the patterns and the system structure that underlie those events.
Section 1: System Components
Components in a system are things that interact, such as plants, animals, water, microbes, nitrogen, and so on. Components may be categorized as abiotic or biotic; components may also be controls. Components each have their own structure function and purpose in the system, all of which must be understood to comprehend the system’s processes, functions, and purposes.
Abiotic Components
Abiotic componen