| Uncertainty, Risk and Ignorance. Uncertainty means we are not sure of what we know. Risk and ignorance are different types of uncertainty. Risk is a type of uncertainty which occurs when we know both the range of outcomes possible, as well as the likelihood of possible outcomes, but not exactly which will occur (as in throwing dice). Pure uncertainty occurs when we know the possible outcomes, but not the likelihood of any particular outcome. And if we do not even know what outcomes are possible, then we are in a condition of ignorance, or absolute uncertainty. |
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| Certainty Regarding Sustainable Scale There is considerable uncertainty regarding many aspects of sustainalbe scale. But with respect to the impact of any specific level of material throughput, we can be certain that scale outcomes will be either sustainable or unsustainable. Given the biopyhsical limits of ecosystems, and the second law of thermodynamics (see Thermodynamic Perspective), we can also be certain that maximum scale is a possible outcome, as a special case of unsustainable scale (see Scale Categories). Being aware of it as a possibility means we can take action to avoid it. |
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| Special Cases of Certainty Regarding Scale There are three special cases we can known with certainty regarding sustainable scale. |
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- We can know with certainty that using non-renewable resources will eventually lead to their depletion. If we know the amount of non-renewable resources available, and the rate of depletion, we can also know with relative certainty, the amount of time until depletion occurs. Estimates of peak oil production are an example (see Energy).
- We can know with certainty that if we exceed the critical level of harvesting of a renewable resource (called depensation), then that resource will eventually collapse. If we know the stock of renewable resource available, the rate of replenishment, and the harvest rate, we can also project the conditions under which such a collapse will occur. Such projections are less accurate than with non-renewable resources (as we have learned with fisheries management) because the complexities involved are greater.
- In the case where ecosystem capacity to absorb a substance is zero or near zero, then we can be certain that the scale of such emissions is unsustainable. Atmospheric ozone depletion provides an example of this phenomena. However, it should be noted that the point where maximum scale might be reached in such special cases remains uncertain.
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| Uncertainty Regarding Scale Determining boundaries for sustainable or maximum scale with any degree of scientific certainty, is at best a long way off. Given the complexities and dynamic interdependencies involved, as well as the many areas of concern, such uncerainties are likely to remain for some time. Indeed, because complex ecosystems are characterized by emergent properties inherent cycles of growth and decay, and nonlinear changes under stress, some uncertainty regarding these boundaries is irreducible.
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| The Role and Limits of Science Better scientific understandings of ecosystem functioning, and human impacts on such systems, are urgently needed to help us assess sustainable scale boundaries. Baseline data for many ecosystems from local to the global levels are seriously wanting. Major scientific efforts to systematicly understand major ecosystems are just beginning (see References, Millennimum Ecosystem Assessment). Likewise, approaching ecosystems from the perspective of Critical Natuaral Capital is also recent. While solid research is needed, asking scale relevant questions is also important. But even with a major global effort, completely understanding sustainable scale boundaries is beyond the ability of science, given the inherent uncertainties involved. |
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| Managing with Uncertainty Accepting the reality of uncertainty and the limitations it imposes are critical to managing our predicament. Accepting both the contributions that more scientific research can provide, and the irreducible uncertainties involved, are important in determining how to best manage the situation. Waiting for scientific certainty in determining sustainable scale boundaries will not be fruitful, but dangerous. Given what we know for certain, the stakes involved, and the availability of Attractive Solutions, the prudent course is to begin managing human activities to ensure we remain within sustainable scale. |
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| Beyond Science No amount of scientific information can ever provide complete answers to a key issue in developing scale relevant policies. Even if science could firmly establish the empirical basis of sustainable scale boundaries (however unlikely), policies would have to be designed to ensure an adequate safety margin to account for unanticipated events that could cause an unplanned transgression of those boundaries. Running a global economy on the threshold of maximum sustainable yield, on the sustainability threshold, is hardly a prudent or safe policy. |
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| Sustainablity a Social and Moral (as well as Scientific) Issue Establishing such a safety margin requires the definition of optimal scale (see Scale Categories), a social boundary within the boundary of biophysical limits. Optimal scale can be developed despite scientific uncertainty about sustainable scale boundaries. Optimal scale is a socio-political construct requiring extensive consultation concerning a variety of issues such as social justice, and responsibility to future generations and other living things. Without some measure of global consensus on this critical issue, there remains the danger of exceeding sustainable scale. There is also the very real danger of some dominant national power or powers, inadvertently or by design, appropriating most available, but ever dwindling, resources for their own survival
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