Systems Theory and Science

            In the 1940s, biologist Ludwig von Bertalanffy presented a novel method for studying natural phenomena called systems theory. Von Bertalanffy proposed systems theory to counter the growing trend of scientific reductionism. Scientific reductionism is a process where a scientist studies a particular phenomenon in isolation from the other phenomena that generally interact with it. The main advantage of this approach is that it allows one to study the phenomenon without background noise from outside cause-and-effect interactions. The disadvantage of this method is that phenomena usually function in environments that include interactions. By removing these interactions, we may only get a partial picture of how these phenomena work in the real world.

            So what is a system? According to systems theory, a system is a group of parts that work together through some process (Figure 1). Within its distinct boundary, a system has three properties: elements, attributes, and relationships. System elements are the kinds of things or substances making up the system. If our system of interest were a freshwater lake, some elements typically found in this type of system include water, fish, dissolved chemicals, insects, algae, and sediment at the bottom of the lake. System attributes are characteristics of the elements that can be perceived and measured. For fish in a lake, attributes may include the quantity, length, and weight of each individual, and the species designation. System relationships are the cause-and-effect associations that exist amongst elements and between their attributes. Finally, the system's state is defined when one or more of its properties (elements, attributes, and relationships) have a distinct value.

            A model is a special type of system. There are two general types of models. Many models are simple, generalized representations of something in the real world. In these systems, details are left out to facilitate quick, easy comprehension of how the phenomenon operates. For example, Figure 1 shows how energy flows from the Sun to Earth, powering the various systems in the atmosphere, hydrosphere, lithosphere, and biosphere. Yet, as we will see later in this textbook, this process is much more complex. The other type of model is also a generalization of reality, but it has one extra feature. It can make predictions or forecasts about the future state of the system's elements or attributes. These predictions are possible because the cause-and-effect relationships that exist between the system's components are understood logically or mathematically. We sometimes refer to these systems as mathematical models or computer models when the calculations are performed on a computer. Some of the problems that physical geographers have applied to computer models include forecasting future weather and climates on our planet, determining the effect of drought on stream flow, and modeling the movement of insect pests in our forests (Figure 2).

            Systems are sometimes visualized through illustrations. In these illustrations, elements and attributes can be sketched as simple component blocks or as other graphical representations. Processes that operate between elements and/or attributes are usually identified by some kind of connection drawn between these parts. Most of the graphic illustrations in this textbook and other science books illustrate systems. Graphical systems are used in this textbook to enhance students' learning. Graphical systems are very effective in explaining how various natural phenomena work because a good illustration can often be worth a thousand words! 

            Scientists have classified many systems according to how they function. Anisolated systemis a system in which no interactions occur outside its boundary layer. Such systems are common in laboratory experiments where chemical reactions are confined to test tubes or beakers. A closed system is slightly different from an isolated system. It does not allow for the transfer of matter into or out of its boundary. But it does allow energy to be transferred across its boundary. Our planet is essentially a closed system. It receives radiant energy from the Sun, which powers various phenomena in the atmosphere, hydrosphere, lithosphere, and biosphere. This energy is subsequently returned to space as longwave emissions. As a matter of fact, our planet is not involved with significant transfers of substances into or from outer space (only an extremely small amount of mass is added to our planet from meteorites and other small celestial bodies). In an open system, both matter and energy can cross the boundary of this entity. Most ecosystems are considered an open system (Figure 3). An ecosystem can be defined as the interaction of different biotic entities with each other and with abiotic components in some area of space. Energy primarily moves into ecosystems through the reception of sunlight and leaves by emitting longwave radiation. Matter can transfer across an ecosystem's boundary by the migration or dispersal of organisms.

System Hierarchy and Interconnections

    

            One of the most important aspects of viewing natural phenomena as systems is the idea of hierarchical interconnectivity. At any level of functionality, a system may be connected to a variety of other systems. Some of these connections could be to phenomena that operate at the same level. Systems can also be connected to a number of smaller systems, each working within its own elements. Within these smaller systems, there could be yet more minuscule systems working towards some other purpose. Thus, at any particular scale of function, a system is connected to other phenomena working at a variety of different scales. These connections are usually active in terms of cause and effect. As a result, the modification of one system's state may have effects that reverberate to systems at other functional levels. This idea is especially important when considered in the context of the unsustainable human manipulation of Earth's various natural systems. Our modification of the Earth's climate through global warming may affect the position of the Earth's jet streams, the number of hurricanes that form over the world's oceans, or the types of plants that you can grow in your garden.

    

            A good example of a system within another system is the hierarchy of systems found in our Universe. Let us examine this system from top to bottom. At the highest level of this hierarchy, we have the system that we call the cosmos or the Universe. The elements of this system consist of galaxies, quasars, black holes, stars, planets, and other heavenly bodies. The current structure of this system is thought to have arisen from an enormous cosmic explosion and is controlled by gravity, weak and strong nuclear forces, and electromagnetic forces. Around some stars in the Universe we have an obvious arrangement of planets, asteroids, comets, and other materials. We call these systems solar systems. The elements of this system behave according to set laws of nature and are often found orbiting around a central star because of gravitational attraction. On some planets, conditions may exist for the development of dynamic interactions between the hydrosphere, lithosphere, atmosphere, or biosphere.

            We can define a planetary system as a celestial body in space that orbits a star and maintains a dynamic balance among its lithosphere, atmosphere, and hydrosphere. Some planetary systems, like Earth's, can also host a biosphere. If a planetary system contains a biosphere, dynamic interactions will develop among the system, the lithosphere, atmosphere, and hydrosphere. These interactions can be called an environmental system. Environmental systems can also exist at smaller scales. A single flower growing in a field could be an example of a small-scale environmental system.

    

            The Earth's biosphere is made up of small interacting entities called ecosystems. In an ecosystem, populations of species form communities and interact with each other and the abiotic environment. The smallest living entity in an ecosystem is a single organism. An organism is alive and functioning because it is a biological system. A biological system consists of cells and larger structures, known as organs, that work together to sustain life. The functioning of cells in any biological system is dependent on numerous chemical reactions. Together, these chemical reactions make up a chemical system. The types of chemical interactions in chemical systems depend on the atomic structure of the reacting matter. The components of atomic structure can be described as an atomic system. 

Systems and Equilibrium

            Earlier in this discussion, the idea of system state was introduced. System state was defined as the measurement of the current condition of an element, attribute, or relationship within a system. If these measurements are recorded over time, we may notice that particular patterns of values emerge. These patterns also represent the average condition or equilibrium of this component. Many different types of equilibrium have been defined (Figure 4). A steady-state equilibrium occurs when the average value of a system component maintains the same trajectory over time. In other words, the average condition of the system's property remains the same over a particular period. The opposite of steady state condition is a dynamic equilibrium. This condition occurs when the average states continually change their values over time. Thermodynamic equilibrium describes a condition in a system where the distribution of mass and energy becomes more disordered and unavailable with time. Our Universe is moving towards this state because energy is being continually transferred into less useful forms. A static equilibrium occurs when the value of a system's property remains unchanged over time. 

            The state of a system's properties is also influenced by disturbances. A disturbance is a type of input that disrupts the usual processes taking place in a system. For example, a fire would disrupt a number of natural processes in a grassland. Plant production of organic matter would be reduced due to plant deaths. This, in turn, would cause grazing animals to go hungry, leading to declines in the size of species populations.  Further, nutrient elements once locked up in organic matter would be converted into ash and gas. Components of a system can recover from a disturbance in two ways. The property could return to the same equilibrium that existed before the disturbance. This condition is known as a stable equilibrium. Or the system could return to a new equilibrium after a disturbance. This situation is called an unstable equilibrium.

FIGURE 3  This pond ecosystem has an obvious boundary located where water meets land and the atmosphere. Despite the presence of this boundary, it is not an isolated system. Actually, this system is quite open to the transfer of energy and matter across these boundaries. For example, energy from the Sun enters this ecosystem when sunlight is absorbed by a layer of water near the pond surface, converting it into heat energy. This heat energy is then transferred throughout the pond by conduction and convection. In fact, water moves in and out of the pond through runoff, precipitation, groundwater flow, and evaporation.  Image Copyright: Darlene Heckl.

FIGURE 2  Shown is a National Oceanic and Atmospheric Administration (NOAA) weather forecast map for United States and southern Canada.  This forecast is for 7 AM Eastern Standard Time on March 13, 1993. An intense mid-latitude cyclone with a low pressure center located near Tallahassee, Florida is shown on the right side of this map. Image Source: NOAA.

FIGURE 1  This simple system visually describes the Earth’s interception of sunlight that was originally generated by processes on the Sun.  Image Copyright: Michael Pidwirny.