|Ecology inspiring engineering - a functional approach|
By Bastian Etter* and Andreas Schoenborn, Switzerland
Good solutions require inspiration. Looking for it can be a tedious endeavour, as we all know. As a technical discipline, engineering relies on a high inspirational input, to quench its thirst for well-applied solutions. However, to find the fitting function, engineering needs to go beyond the inherent technology. In the case of ecological engineering, the employed technologies are claimed to be ecological. As a consequence, ecological engineers may find appropriate answers in ecology, and particularly, in ecological systems.
How does engineering become ecological? When can a technology considered to be ecological? A technology considered to be ecological has to do more than just show respect or benefit the environment. It has to be embedded into existing ecosystems, considering that we as humans and our constructions are also part of the globe's ecosystems.
To understand how a constructed ecosystem or part of it can be embedded into an existing ecosystem, it is important to first understand the basic principles and functions of natural ecosystems, as various authors have outlined. In a second step, functions for the constructed ecosystems can be deduced from functions encountered in nature.
In this regard, Winfried E. H. Blum, emeritus professor of soil sciences, proposes to "let us see how nature works", given that "the essential governing principles of the biosphere can provide some guidance in ecological engineering". However, when engineering ecosystems, one has to be careful to differentiate functions from these governing principles. The functions result from the principles, so the question to ask is, what is nature's method to fulfil a certain function.
Besides Professor Blum, numerous other authors have tackled to define ecological engineering. Although interpretations differ, a basic pattern can be identified based on ecological principles and functions. The following enumeration is an attempt to find a common denominator for several sources, such as Todd (1993), Heeb (1994), Mitsch & Jørgensen (2004), Blum (2007), or Dakers (2007). The described criteria are summarised in table 1:
Table 1: Summary of the criteria applied to ecological engineering by various authors. The letters in brackets indicate authors, who mention the criteria. The wording of certain criteria was changed to allow for comparison among the authors.
Authors: T: Todd & Todd (1993); H: Heeb (1994); B: Blum (2007); D: Dakers (2007); M&J: Mitsch & Jörgensen (2004);
Network structure: avoid dissipation
Ecosystems are arranged in a complex network structure. As a basic principle, all ecosystems are open and connected systems, and within each system, the components are interconnected among themselves. The global system is a stunning mosaic of decentralized systems of diverse habitats with diverse populations and diverse functions.
The function of this reticulation is to recycle energy and materials, thereby closing the loops and avoiding dissipation. The only input of energy reaching the globe's ecosystems is of solar origin. To maximize the gain from solar energy, nature has set up a wise system of renewing energy and reusing material, with each living organism getting its share. Thus, food webs recycle energy and materials from the very source of photosynthesis, across numerous echelons, all the way to decomposition.
In ecological engineering, a construction has to be conceived both as an ecosystem itself and as part of the network within a larger ecosystem. The network weaved within the ecological engineering structure assures multi-functionality and recycles materials and energy on the spot. In a broad perspective examining the embedding of an ecological engineering construction, it can be the missing link to close the loop, where conventional technology has previously created a linear material or energy flow. For instance, a treatment wetland is an ecosystem designed to remove pollutants and nutrients from wastewater, and is as such embedded in a wider ecosystem, where it takes the role of recycling water into the water cycle.
Diversity: create and maintain stability
The network structure provides the substrate for a maximum of variety. Interlinked habitats create ecotones and niches, where diverse species can form. Among living organisms, both specialists and generalists can be found. They weave the network at various levels, each of them having its functions and raison d'être. Nature has established diversity as a response to the diversity of habitats, and has adapted diverse survival strategies to diverse environmental challenges. With its multitude of well-thought solutions, an ecosystem diversifies its assets, creating a powerful life insurance.
In ecological engineering, diversity can be found both in technology and approaches. On one side, technology needs to build upon regional singularities, inevitably producing diverse outcomes. Ecological engineering follows a strong call to look for locally apt solutions. On the other side, diversity is also the approach to ecological engineering, which makes use of both a range of experts from diverse science and engineering disciplines and local knowledge.
Homeostasis: react to changes
When looking at ecosystems on a time scale, one observes a dynamic adaptation within the system and to environmental factors, so-called forcing functions. By virtue of its network and diversity, an ecosystem shows the capacity to resist to stress or respond with resilience to a changing environment. It thereby tends back to towards a steady state or equilibrium, once it has experienced a disturbance. Although the dynamics of an ecosystem in their totality may be impossible to grasp, in many aspects, nature is able to auto-design or auto-organize oneself and establish a functioning system through the interaction of species among themselves and with the environment.
Ecological engineering takes advantage of the natural homeostasis, by deliberately leaving nature the freedom to grow into the constructed ecosystems. The ecological engineer may want to provide a certain guidance by setting the scene. Though, in any constructed ecosystem, the most adapted species will establish themselves striving towards the system's equilibrium. The art in ecological engineering is to match that equilibrium with the objectives of the project and use the function of natural homeostasis.
Now, what does this all mean for ecological engineering? How can we create systems that fulfil these principles and functions? When looking at criteria to define ecological engineering, we realize that the criteria themselves are a complex system. As a logic conclusion, the nature of ecosystems reverberates on their definition. In the three formulated principles we recognize interdependence: in other words, networks maintain diversity, diversity brings about homeostasis, and homeostasis knits networks. By looking closely at nature's function, we may find the necessary inspiration on how to connect principles and functions for our ecological engineering projects and close the cycle.
Editor's note: This article has been published as the second of a series of articles on "new solutions by transforming traditional ways of thinking", following-up the IEES symposium 2012
|Last Updated ( Wednesday, 17 October 2012 )|