2.3 Design of ecological engineering

2.3.1 Concepts of system

A system is a set of interacting or interdependent components forming an integrated whole or a set of elements (often called components) and relationships that are different from relationships of the set or its elements to other elements or sets. Some systems share common characteristics, including: a system has structure, it contains parts (or components) that are directly or indirectly related to each other; a system has behavior, it contains processes that transform inputs into outputs (material, energy or data); a system has interconnectivity, the parts and processes are connected by structural and/or behavioral relationships; a system’s structure and behavior may be decomposed via subsystems and sub-processes to elementary parts and process steps. Input, output, processor, control, feedback, boundary and interface, and environment are considered as the elements of a system in terms of information systems.

Environment and boundaries

Systems theory views the world as a complex system of interconnected parts. We scope a system by defining its boundary; this means choosing which entities are inside the system and which are outside - part of the environment. We then make simplified representations (models) of the system in order to understand it and to predict or impact its future behavior. These models may define the structure and/or the behavior of the system.

Natural and human-made systems

There are natural and human-made (designed) systems. Natural systems may not have an apparent objective but their outputs can be interpreted as purposes. Human-made systems are made with purposes that are achieved by the delivery of outputs. Their parts must be related; they must be “designed to work as a coherent entity” - else they would be two or more distinct systems.

Theoretical framework

An open system exchanges matter and energy with its surroundings. Most systems are open systems, like a car, coffeemaker, or computer. A closed system exchanges energy, but not matter, with its environment; like the earth or the project Biosphere 2 or 3. An isolated system exchanges neither matter nor energy with its environment. A theoretical example of such a system is the Universe.

Process and transformation process

A system can also be viewed as a bounded transformation process, that is, a process or collection of processes that transforms inputs into outputs. Inputs are consumed; outputs are produced. The concept of input and output here is very broad. For example, an output of a passenger ship is the movement of people from departure location to destination.

Subsystem

A subsystem is a set of elements, which is a system itself, and a component of a larger system.

System model

A system comprises multiple views. For man-made systems it may be such views as planning, requirement (analysis), design, implementation, deployment, structure, behavior, input data, and output data views. A system model is required to describe and represent all these multiple views.

System architecture

A system architecture using one single integrated model for the description of multiple views such as planning, requirement, design, implementation, deployment, structure, behavior, input data, and output data views, is a kind of system model.

2.3.2 Concepts of engineering

Engineering is the application of scientific, economic, social, and practical knowledge in order to design, build, maintain, and improve structures, machines, devices, systems, materials and processes. It may encompass using insights to conceive, model and scale an appropriate solution to a problem or objective. One who practices engineering is called an engineer.

Engineering is a key driver of human development and bound up with society and human behavior. Every product or construction used by modern society have been influenced by engineering. Engineering is a very powerful tool to make changes to the environment, society and economies, and its application brings with it a great responsibility.

Engineering is quite different from science. Scientists try to understand nature. Engineers try to make things that do not exist in nature. Engineers stress invention. To embody an invention the engineer must put his idea in concrete terms, and design something that people can use. Something can be a device, a gadget, a material, a method, a computing program, an innovative experiment, a new solution to a problem, or an improvement on what is existing. Since a design has to be concrete, it must have its geometry, dimensions, and characteristic numbers. Almost all engineers working on new designs find that they do not have all the needed information. Most often, they are limited by insufficient scientific knowledge. Thus they study mathematics, physics, chemistry, biology and mechanics. Often they have to add to the sciences relevant to their profession. Thus engineering sciences are born.

Contemporary technologically advanced civilization has made massive changes in the environment. Land is to be developed. Raw land is to be improved. Natural resources are to be exploited and consumed. Trees are to be harvested. The rivers are to be harnessed to produce electrical power. The wilderness must be managed. Nature, like the rest of the non-human world, is to be subservient to human purposes.

2.3.3 Design principles of ecological engineering

Design principles of ecological engineering below is abstracted from paper written by Bergen, Nolton and Fridley.

Design consistent with ecological principles

Designs produced with regard for, and taking advantage of, the characteristic behavior of natural systems will be most successful. When we include and mimic natural structures and processes, we treat nature as a partner in design, and not as an obstacle to be overcome and dominated.

We are all familiar with the second law of thermodynamics and the concept of entropy. Perhaps the first law of biology is that life is a negentropic process. Life causes local decreases in entropy by producing order out of chaos. The second law is not violated because the energy expended to produce order results in more entropy overall. The practical implication, however, is that an ecosystem has the capacity to self-organize. Mitsch and Jørgensen state that it is this “capability of ecosystem” that ecological engineering recognize as a significant feature, because it allows nature to do some of the engineering. We participate as the choice generator and as a facilitator of matching environments with ecosystems, but nature does the rest.

Self-organization is manifested through the process of succession in ecosystems. Todd discusses how as ecosystems mature, connections between components become more numerous and complex, with the system becoming more diverse and resistant to perturbation. They describe current design practices as “early successional”, with simple linkages and patterns, and no room for maturation. Designs are then more susceptible to disturbance and failure. Kangas and Adey propose that mesocosms (scale range m2 to ha) most clearly express the self-organization of ecosystems and provide experimental units that will be critical for ecological engineering and restoration ecology.

The key ecosystem attributes that allow for self-organization are complexity and diversity. Ecosystems can be complex structurally and in the temporal and spatial scales of processes. Significant ecological change is episodic, and critical processes occur at rates spread over several orders of magnitude, but clustered around a few dominant frequencies. Ecosystems are heterogeneous, displaying patchy and discontinuous textures at all scales. Ecosystems do not function around a single stable equilibrium. Rather, Holling states that, “destabilizing forces far from equilibria, multiple equilibria, and absence of equilibria define functionally different states, and movement between states maintains structure and diversity”. The structure and diversity produced by the large functional space occupied by ecosystems is what allows them to remain healthy, or to persist.

The large functional space required for sustainable ecosystems is directly at odds with traditional engineering design practices that create systems that operate close to a single, chosen equilibrium point. Holling uses this idea to distinguish between what he terms engineering resilience and ecological resilience. Engineering resilience measures the degree to which a system resists moving away from its equilibrium point and how quickly it returns after a perturbation. Ecological resilience reflects how large a disturbance an ecosystem can absorb before it changes its structure and function by changing the underlying variables and processes that control behavior. The equilibrium conditions discussed above for ecosystems exist within the range of ecological resilience.

The distinction between the two types of resilience is important because management policies that force ecosystems to function in a state of engineering resilience lead to a loss of ecological resilience. Systems managed to produce a consistent, high yield of a single variable (such as timber or fish) lose the functional and structural diversity required to remain ecologically resilient. The system is then more susceptible to “failure”, where it may lose the ability to produce the same outputs in the future.

Diverse systems are more ecologically resilient and able to persist and evolve. Diversity can manifest in terms of the number of species, genetic variation within species and as what Holling calls functional diversity. Functional diversity is another way of saying redundancy, where a number of species or processes in the system can perform similar functions. If one is impaired then others fill the void contributing to the ecological resilience of the system. The implication here is to maintain diversity in managed systems and alludes to the classic quote from Leopold, “To keep every cog and wheel is the first precaution of intelligent tinkering”.

Another important characteristic of ecosystems is that the outputs of one process serve as the inputs to others. Little waste is generated and nutrients are cycled from one trophic level to the next. The field of industrial ecology is principally based on this concept.

A final characteristic of natural systems is that they tend to function near the edge of chaos or instability. Systems operating near the edge can take better advantage of evolutionary opportunities. Cairns notes that our current technological systems have co-evolved with ecosystems and that introducing chaos into one system will likely lead to chaos in the other. Designing systems to include ecological characteristics departs from common engineering practice. Designing for ecological rather than engineering resilience means encouraging diversity and complexity and allowing systems to self-organize, mature, and evolve. How to design systems to perform like ecosystems and still function as desired is explored in the remaining principles.

Design for site-specific context

The complexity and diversity of natural systems cause a high degree of spatial variability. While the ecological characteristics discussed above are generally applicable, every system and location is different. The second principle can be stated in a number of ways, but boils down to the idea of gaining as much information as possible about the environment in which a design solution must function. Spatial variability precludes standardized designs, so solutions should be site-specific and small-scale.

Standardized designs imposed on the landscape without consideration for the ecology of a place will take more energy to sustain. Berry sums up this principle succinctly: there are, I think, three questions that must be asked with respect to a human economy in any given place: What is here? What will nature permit us to do here? What will nature help us to do here?

Knowledge of the place also allows for more holistic designs. Todd refers to the Gaia hypothesis that the earth is a complex, living organism with all its components interconnected. Ecological design considers both the upstream and downstream effects of design decisions—upstream in that we consider what resources must be imported and appropriated to create and maintain a solution, and downstream in our consideration of the site-specific and off-site impacts of the design on the environment. In addition to the physical context of a design, knowledge of the cultural context is important. Designs are more likely to succeed and to be accepted by the local community when the people who live in a place are included in the design process. They bring knowledge of the particularities of a place and are empowered through direct participation in shaping their environment. Attention to group dynamics and conflict mediation is important for successful stakeholder participation.

Maintain the independence of design functional requirements

Ecological complexity adds high and often irreducible levels of uncertainty to the design process. Even under conditions of certainty, the amount of relevant information we possess may be overwhelming and unmanageable. We want to keep solutions simple and workable. A strategy for dealing with uncertainty is to set the tolerances on our design functional requirements as wide as possible.

The third principle is a restatement of the first design axiom of Suh. In the realm of mechanistic engineering design, where this axiom originates, it appears very straightforward and easy to grasp. Functional requirements (FRs) are the specific functions that we wish a design solution to provide. Design parameters (DPs) are the physical elements of the solution chosen to satisfy FRs. Best designs are those that have independent (not coupled) FRs and one and only one DP to satisfy each FR. When modifying one DP affects more than one FR, a design is coupled.

In circumstances where there is functional coupling, wide tolerances on FRs can make the design essentially uncoupled. Wide design tolerances allow a larger functional range for a system while the outputs remain within acceptable ranges. This is another important aspect of designing for ecological rather than engineering resilience. Systems designed for engineering resilience often have tight tolerances. When interacting with ecological systems, however, the concept of functional independence becomes a lot less clear. Ecosystems are complex with many levels of interconnection between components. Many elements of the system may be involved in more than one process. We must not confuse ecosystem functionality with design FRs. Ecosystems can function and provide benefits to society without human intervention. We undertake the process of design to satisfy unmet human desires, and the FRs for design follow from the statement of these needs. Ecosystem processes that presently exist that we wish to preserve while we design for unmet needs act as constraints on design. The independence principle states that we are more likely to have successful designs when we can keep the FRs uncoupled in the solution. In reality, however, it would be foolish not to take advantage of the multiple, coupled services an ecosystem can provide.

Design for efficiency in energy and information

The fourth principle follows from taking advantage of the self-organizing property of ecosystems. To let nature do some of the engineering means that we should make maximum use of the free flow of energy into the system from natural sources, primarily the sun. Conversely, we want to minimize the energy expended to create and maintain the system directed, by design, from off-site sources, such as fossil fuels, and large-scale hydroelectric sources. While utilizing free flowing energy, however, it is important to follow where the energy would go without intervention, to make sure that it is not more critically needed downstream and that there is minimal adverse impact.

Similar to the flow of energy, the second design axiom proposed by Suh states that we want to minimize the information content of a design. The ideas and principles we have discussed so far all relate to minimizing information, or making designs simple yet successful. When we cooperate with natural processes and allow systems to self-organize, it requires less energy and information to implement and maintain a design. Meeting wide tolerances requires less information. In the case of stream restoration, high-energy inputs to control system structure or function are counterproductive to the ecological resilience and performance of the non-emphasized functions of the system. For example, the energy input needed from humans to restrict a stream channel to a confined space tends to be high and ultimately unsuccessful when a large flood occurs. A better design would recognize the expected variability in stream flows and design the system to withstand large variations in flow (wide tolerance) and still maintain its ecological and engineering functions.

Minimizing information content appears contrary to encouraging diversity and complexity in design solutions. The extra information required, however, is balanced by utilizing self-organization and wide tolerances. We can consider it an upfront capital investment in diversity to gain overall efficiency later through reduced energy requirements and a reduced risk of failure. Diversity provides insurance against uncertainty in addition to contributing to ecological resilience, as discussed in the first principle. In the case of an engineered wetland, for example, a wide range of species may be included in the initial construction, but natural processes are allowed to select those best suited for the imposed environment. Similarly, the first and second principles advocate an up-front investment in knowledge of the design context to minimize uncertainty and to allow less information to be transferred during design implementation.

Acknowledge the values and purposes that motivate design

The definition of ecological engineering we advocate states that design is practiced for the benefit of both society and the natural environment. Most engineering codes of ethics state at least that engineers have a responsibility to serve and protect society. We have explicitly broadened that responsibility to include the natural systems that support life. Regardless of specific ideology, however, design practices that acknowledge the motivating values and purposes will be more successful.

Proponents of an ecological approach to design are passionate in their arguments, relying as much on scientific observation as on ideology, morality, ethics, and spiritual beliefs. Three of the nine precepts proposed by Todd and Todd are value statements. Ecological design invites and embraces the qualitative, the uncertain, and the non-rational aspects of human nature. Goals such as connection to place, equity, sustainability, and esthetics are as important as material output. While those writing about ecological design hold a variety of values, there is agreement at least on how to respond to risk and uncertainty. When dealing with the natural environment, many engineering decisions result from what can best be characterized as hubris. The term hubris seems most fitting because it implies not only overconfidence, but also that retribution may occur as a result. Herman uses the term revenge to describe how our attempts to manage complex systems always seem to produce unexpected and unwanted side effects. Costanza warns that the worst form of ignorance is misplaced certainty. The third principle recommends using wide tolerances under conditions of uncertainty. From a value standpoint, we also recommend adopting a precautionary approach for ecological engineering. A precautionary approach will act as a form of insurance against unpleasant surprises in the future. Engineering would be applied sparingly, and complex solutions avoided where possible. To avoid catastrophic failures, design solutions that are both fail-safe and safe-fail should be pursued. As opposed to traditional fail-safe approaches safe-fail solutions acknowledge that our original functional requirements for a design may not be met or that there may be unexpected results, but failure in this case is not catastrophic. Costanza advocates selecting design alternatives that have the best worst-case outcome. The precautionary approach has also been expressed as shifting from minimizing type-I error to minimizing type-II error. It is the scientific norm to achieve high levels of confidence in a hypothesis before it is accepted (minimizing type-I error). When applied to environmental management this means that we would need almost complete certainty in a hypothesis of ecological damage resulting from engineering activity before we would accept the hypothesis. Minimizing type-Ⅱ error would shift the burden of proof to the hypothesis that damage is not occurring. Shrader-Frechette spells out a number of reasons why the choice of minimizing type-Ⅱ error is an ethical preference. The reasons include concepts of intergenerational equity, equitable distribution of risk, and concern for non-human species.

2.3.4 Mulberry dyke fish ponds

The mulberry dyke fish ponds are traditionally managed mulberry growing, sericulture and fish farming. Since the 16th century, they have been built in low-lying land area in Southern China. These designs fully utilize natural resources to maximize production outputs without detriment to plants and animals in the process.

The mulberry dyke fish pond eco-system serves two major functions: achievement of a general ecosystem balance through the harmonization of well-coordinated activities and functions embedded in the ecosystem; and transformation and regeneration of organic substances based on a multi-layer trophic ecosystem structure, which helps contribute successfully to sustainable economic development.

The mulberry dyke fish pond complex contains two interrelated systems of dyke and pond; the dyke is the land ecosystem for the growth of mulberry trees whereas the pond is the water ecosystem, consisting of fish and aquatic plants. Mulberry leaves are fed to the silkworms, whose excreta are used as fish food, and the fertile pond mud—consisting of fish excreta, organic matter, and chemical elements—is brought up from the bottom and used as manure for the mulberry trees. The mutual benefits of each link in the system have been known to the farmers of the area for many years, as reflected in the folk saying that “the more luxuriant the mulberry trees, the stronger the silkworms and the fatter the fish; the richer the pond, the more fertile the dyke and the more numerous the cocoons.” In this system, the mulberry tree represents the first trophic level. Photosynthesis takes places in its leaves, which are fed to the silkworms (the primary consumers) whose excreta and chrysalises are in turn fed to fish (the secondary consumers). The aquatic organisms in the pond are the reduction agents that decompose fish excreta and algae, break down the organic matter in the pond, and produce nitrogen, phosphorus, and potassium. These are then returned to the mulberry dyke when pond mud is used as fertilizer (Fig.2.3.1).

Traditional mulberry dyke fish pond practice has been proven to be an environmentally friendly and sustainable sericulture method because it maximizes production on a continual basis, improves water quality and reduces serious flooding in the low-lying land, avoids over-feeding and the misuse of chemical fertilizer, and provides natural food for the silkworms and fish within the interrelated ecosystem.