Sustainability science is a new academic discipline that draws on many previous insights and methods from environmental science, ecology, geology and many other areas to try and understand and develop analytical frameworks for dealing with sustainability within socio-ecological systems. As such the idea of sustainability offers us one approach with which to understand the complex interaction between society and ecosystem.1 The rise of the term sustainability over the past few decades has been phenomenal, as it has rapidly gone from the fingers to the center of attention within policy making and the media of many countries. The number of times the word occurs in a book publication has shown a stellar take off since the late 80’s. In the research literature sustainability articles also started growing rapidly beginning in the early 1990s and have been doubling about every 8 years since.2
Modeling sustainability through society-nature interactions is an inherently complex process the analysis of which requires inter and transdisciplinary efforts. The philosophical and analytic framework of sustainability draws on and connects with many different disciplines and fields; in recent years this has formed into an area that has come to be called sustainability science. Which has been described as, “…an emerging field of research dealing with the interactions between natural and social systems, and with how those interactions affect the challenge of sustainability: meeting the needs of present and future generations while substantially reducing poverty and conserving the planet’s life support systems.”
Research relevant to the goals of sustainable development has long been pursued from bases as diverse as geography and geochemistry, ecology and economics, or physics and political science. Increasingly, however, a core sustainability science research program has begun to take shape that transcends the concerns of its foundational disciplines and focuses instead on understanding the complex dynamics that arise from interactions between human and environmental systems and how they give rise to more or less sustainable outcomes.
One of the great challenges to sustainability science today is in trying to develop generic models that capture the essential variables and interactions between society and ecosystem that affect the system’s overall sustainability within some overarching framework. Socio-ecological systems are inherently complex assemblages that are spatially heterogeneous and change over time according to an intricate interplay of a large number of biophysical as well as socioeconomic factors, effectively modeling them requires systems based holistic approaches that are able to integrate the many different perspectives involved.
Sustainability can be defined as the ability to be sustained, supported or upheld. In more general terms, sustainability is the endurance of systems and processes. When we talk about sustainability in the abstract we are really talking about the state of a system over time, we are asking about how long the system or process can continue at the current level of functionality before it becomes degraded to a low level of functionality. For a system to be sustainable, or what we might call viable, it has to be consuming at or less than the aggregate level of production to whatever resource is sustaining it, equally it has to be able to adapt to its changing environment. On its most basic level this question of sustainability is an equation between what is being consumed and what is being produced, but of course, this is a very complex equation when we are talking about a whole economy and supporting ecosystem with many interacting, moving parts.
The variables that we have outlined loosely correlate to those used in the first such macro model to global sustainability, which was published in a book called The Limits to Growth in 1972. The original version presented a model based on five variables: world population, industrialization, pollution, food production and resources depletion. But of course, sustainability is much more than just about technology, demographics and natural resource supply, just as important as the basic physical mechanics is a society’s capacity to adapt and evolve in response to changes. From this perspective sustainability is not so much about trying to make everything add up, trying to reduce ecological footprint or make technology more efficient, but instead recognizing that change is an inherent part of the socio-ecological dynamic and that long-term sustainability is only really going to come through enabling an effective adaptive mechanism within the social system in order to evolve in response to changes in the ecosystem and thus endure over time. Adaptation engages both economic, social and cultural domains, on all levels it requires feedback loops so that people and institutions can receive information and respond to it, seeing the effects of their actions and the state of the environment.
One of the first things to add to this model is the fact that the population is changing over time, the rate of growth to a population and its change is typically understood within population ecology with reference to the logistic map, where the rate of population growth is proportional to both the existing population and the amount of available resources, all else being equal. The mathematician Verhulst derived his logistic equation to describe the self-limiting growth of a biological population. By adding this into the dynamic we get one basic understanding of sustainability in terms of what is called the carrying capacity, where the carrying capacity of a biological species in an environment is the maximum population size of the species that the environment can sustain indefinitely, given the ecosystem services available in that environment. The carrying capacity can be defined as the environment’s maximal load up to which the population can grow and exist sustainably.
To develop a more representative model we would also have to recognize that the stock, which is the ecosystem, is not just a static variable but in fact has a generative capability, the capacity to reconfigure and regenerate itself. So there are really two factors here, the stock of resources or ecosystem services that flow to the economy at any given time, but also there is the system through which those services are generated. This is called natural capital. A functional definition of capital, in general, is: “a stock that yields a flow of valuable goods or services into the future”. Natural capital is thus the stock of natural ecosystems that yields a flow of valuable ecosystem goods or services into the future. For example, a stock of trees or fish provides a flow of new trees or fish, a flow which can be sustainable indefinitely. Natural capital may also provide services like recycling wastes or water catchment and erosion control. Since the flow of services from ecosystems requires that they function as whole systems, the structure, integrity, and diversity of the system are important components of natural capital. Thus the supply of ecosystem services can change when we affect the systems that provide them and these critical ecosystem functions can often change in a nonlinear fashion, with tipping points and thresholds.
The next important factor to include into the model is that unlike with the simple boat model where resources are consumed and just disappear, in reality economies are dissipative systems, that means during their operation they generate entropy and this entropy has a degrading effect on the functionality of the ecosystem’s natural capital over time. This means we need to think not just about how much the system is consuming but also just as importantly the level of efficiency to the system. Here we are talking about efficiency as a ratio between the total resources consumed and the total entropy exported. The scale of impact that an economy has on the natural environment is attempted to be captured in a model called I = PAT which is the lettering of a formula put forward to describe the impact of economic activity on the environment. It posits that economic impact on the environment is equal to P which is for the total size of population, A which is for their affluence, representing the average consumption of each person in the population, and T which is for technology, representing how resource intensive the production of this affluence is.3
This may go someway to describing the basic physical mechanisms to the sustainability dynamic, an equation representing a core set of constraints between a number of different factors including, the size and functionality of the ecosystem and thus the quantity of ecosystem services, the quantity of population and their level of consumption, how efficiently the economy’s technology infrastructure processes those resources and thus the amount of waste produced and the environment’s capacity to deal with those effects without degrading the society’s natural capital. But sustainability is much more than just about technology, demographics, and natural resource supply, just as important as the basic physical mechanics is a society’s capacity to adapt and evolve in response to changes. From this perspective sustainability is not so much about trying to make everything add up, trying to reduce ecological footprint or make technology more efficient, but instead recognizing that change is an inherent part of the socio-ecological dynamic and that long-term sustainability is only really going to come through enabling an effective adaptive mechanism within the social system in order to evolve in response to changes in the ecosystem and thus endure over time. Adaptation engages both economic, social and cultural domains, on all levels it requires feedback loops so that people and institutions can receive information and respond to it, seeing the effects of their actions and the state of the environment.
On its most basic level, the market economy engineers an adaptive capacity in the pricing systems. In general, as a commodity or service becomes more scarce the price increases and this acts as a restraint that encourages efficiency, technical innovation, and alternative products. However, this only applies when the product or service falls within the market system. As ecosystem services are often treated as economic externalities they are unpriced and therefore overused and degraded. The pricing of ecosystem services then is an important part of enabling this feedback loop to function, as long as ecosystem services are externalized the market has no signal or way of sensing their state and thus no way of responding and adapting as needed. And this broken feedback loop has been a major critic of the free market system and identified as a central cause of current environmental problems on the global scale.4
But markets have their limitations. They are not effective at dealing with situations that involve some form of commons, such situations require social capital, the value that is stored in social bonds that enable effective communications, reciprocity, and coordination. Social capital is central to dealing with tragedy of the commons problems that otherwise can be very environmentally costly and very inefficient to try and manage through the market. Self-organizing communities that effectively use their social capital become more sustainable, effective, and resilient than those with adaptation mechanisms designed and imposed by external entities. The published literature contains many examples that demonstrate not only the ability of social capital to provide the needed power for the management of common community property or resources such as water, pastures, forests etc. but also to build an adaptive capacity to better tolerate climate variability as well as climatic hazards and extreme events. Case studies to the management of Sea defenses in Vietnam during the 90’s among others have shown how in the time of crisis the dormant social capital was rapidly awakened by the communities themselves and plays an important part in dealing with the change. Social capital enables the community to self-organize from within and use their social capital to build adaptive capacity to be more sustainable, effective, and resilient than those with adaptation mechanisms designed and imposed in a top-down fashion.
Sustainability and Adaptation also has a strong cultural dimension to them, society’s capacity to adapt is strongly correlated to how it understands itself and through this its relation to the natural environment. People’s identity plays a very significant role in defining their capacity to adapt to changes within their natural environment. There is a recognized need to expand understanding of subjective dimensions to recognize the values and lived experiences of people in a place. Most investigation into climate adaptation to date has focused on specific technological interventions and socio-economic aspects of adaptive capacity. New perspectives posit that socio-cognitive factors may be as or more important in motivating individuals to take adaptive actions. In a recent piece of research conducted in rural Mexico, one of the authors undertook in-depth interviews with a sample of farmers to explore their perceptions of their social identity and climate risk. These interviews showed robust evidence that social identity mediates between risk perception and adaptation through its influence on motivation. Interviews revealed significant links between social identity and perception of information, risk perception, and ultimately adaptation.5