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What Scale Relevant Lessons Should We Take from the Atmospheric Ozone Depletion Story?


An Instructive Example

The atmospheric ozone story provides several relevant lessons from a scale perspective:


  • When the absorptive capacity of a critical ecosystem is essentially zero for the substance emitted, then zero throughput is the only sustainable level
  • Apparently innocent appearing compounds can seriously degrade critical global ecosystems
  • Rare substances can be vital to life support systems
  • Preventing scale problems is preferable to fixing them after they occur
  • Understanding ecosystems dynamics prior to engaging in activities that may jeopardize their functions is important
  • Maximum scale does not have to be know for relevant policy decisions to be made
  • Sustainable scale and optimal scale may be the same
  • Ensuring compliance with sustainability targets is of vital importance.

 Let us explore each of these lessons to allow the benefits of hindsight to be applied in the future.


Zero Absorptive Capacity Means Zero Throughput

The first lesson from the atmospheric ozone depletion story is that any substance for which the absorptive capacity of affected critical ecosystems is zero should be banned.  If the absorptive capacity of a critical affected ecosystem is zero, than the sustainable scale of throughput for that substance is also zero. The loss of critical ecosystem functions is unacceptable and their preservations must be the overriding default priority.


Attractive Compounds Can Degrade Critical Ecosystems

CFCs were attractive because they replaced some known harmful substances used for refrigeration in the early part of the 20th century.  Their widespread use allowed for refrigeration to develop and spread rapidly and widely.  CFCs were believed harmless because they were inert substances and therefore not likely to affect biological processes. 


As it turned out, it was precisely these inert properties that contributed to ozone depletion, drawing to attention our dependence on abiotic global cycles as well as on biological processes.  The attractiveness of CFCs as a “safe” refrigerant (compared to what had previously been used), and the commercial potential of this new compound, obscured the potential downside and may have inhibited exploration of negative effects.


The next lesson is that any new compound must be considered from the perspective of potentially critical ecosystem impacts. There are several steps such a process might involve:


  • Identification of potential ecosystems that might be affected
  • Identification of the functions those ecosystems provide in terms of life support services (including all living systems, and their interdependencies with non-living systems)
  • Determination as to whether any of the ecosystem functions identified are critical (see Critical Natural Capital) (i.e. are essential in terms of life supports, and if lost could not be replaced – either in terms of substitution or in terms of reversibility)
  • Life cycle analyses of the compound to determine impacts from extraction of materials to make the compound, production and use of the compound, and eventual disposal of the compound
  • Where empirical data are lacking, rules are needed about how to proceed (e.g. under what circumstances should use of the compound be banned or limited until such data are available; can simulations be safely used to estimate ecosystem impact; under what circumstances should empirical trials be conducted in order to examine the potential for negative impact; is a substitute possible that would clearly be a safer choice?)

Essentially we need to ensure that simply because a new compound has obvious benefits, potentially negative consequences for critical ecosystem functions are not ignored prior to widespread use. 


Size Does Not Matter

If the entire ozone layer, which extends between an altitude of 20 to 30 kms above the earth’s surface, were compressed it would be no more than 3mm in thickness.  Despite the apparent fragility of this distant and invisible trace gas it is essential to life on the earth’s surface.  The lesson here is that we cannot take for granted any component of our biosphere in terms of its importance to life support functions.  Given our current state of knowledge/ignorance we come to understand their importance only after we have begun to destroy them.  In the case of critical life support functions, this may be too late.


Prevention Preferable to Rehabilitation

Theoretically sound warnings of CFCs’ potential to adversely affect the atmospheric ozone layer were made as early as 1974 (Rowland and Molina 1974), prior to any significant damage being recorded.  If the precautionary principle had been applied, then greater emphasis would have been given to finding a less harmful substitute.  Such a substitute was found fairly quickly once empirical evidence was available that a serious problem existed.


It should also be noted that discovery of the empirical evidence was almost accidental and if it had not occurred when it did, considerable damage to human and other life forms would have been the first warning signs.  If an R&D effort had been triggered by the theoretical concerns raised by Rowland and Molina and others, then much of the damage spread over several decades could have been avoided.  Unfortunately, commercial interests trumped the precautionary principle and sound theory was discarded. 


It did not take many years of CFC use to begin degrading the atmospheric ozone layer.  But even if a complete ban on all ozone depleting compounds was effectively implemented today, the problems would persist for decades.  This is because once the compounds are emitted they can take years to reach the upper atmosphere where the depletion occurs, and they remain active for many additional years.  Restoration of ecosystem functioning, once disruption occurs, appears to be a very long term process.  All the while damages to various plants, animals and humans will continue.


Another lesson to emerge from this perspective is to avoid scale problems if at all possible. Once ecosystem dynamics are disrupted it is difficult if not impossible to reestablish previous equilibriums. One scale problem can interact with other scale problems (as for example, atmospheric ozone depletion interacts with climate change).  Seek sound theory about the potential impacts of a new substance or process before it becomes widespread.  Test the theory empirically in a safe way prior to widespread use of a new substance or process. If a reasonable theoretical formulation can be made about a potential scale impact, give serious consideration to the precautionary principle.


Understanding Ecosystem Dynamics

It is interesting to note that despite earlier warnings based on theoretical considerations (e.g. Arrenhius in 1897 regarding climate change; and Rowland and Molina in 1974 regarding atmospheric ozone depletion), each of the major scale problems were not addressed until some destruction of living systems actually occurred.  While our scientific knowledge of ecosystem dynamics is still in early stages, we currently know enough to make reasonable estimates of potential problems arising from various human activities.


There is currently no requirement that such considerations be made before the introduction of new chemical compounds, nor are there any requirements for apparently benign human activities to be examined from a scale perspective in terms of their cumulative effect.  Current legislation and international agreements deal with some known substances where considerable damage is already evident (e.g. recent Persistent Organic Pollutants, or POP, treaty).  But scale relevant questions are not being asked routinely regarding impacts on ecosystem functions.


The lesson to be drawn from the ozone story is that we need a comprehensive and systematic approach to approving new compounds and processes in terms of their potential impacts on critical ecosystem functions.


Identifying Maximum Scale and Taking Action

Maximum scale is a useful concept because it identifies the point of no return in terms of the irrevocable loss of critical ecosystem resilience. However, our current knowledge of ecosystem function is such that we cannot identify the specific levels of throughput (e.g. the amount of ozone depleting compounds) that would trigger this catastrophic event. 


The atmospheric ozone depletion story demonstrates that we do not need to have specific information about the precise measurement of maximum scale to know we have a scale problem, or to begin solving it.  Nonetheless, the conceptual framework which includes maximum scale as an extreme value to be avoided because of the dire consequences associated with it, is helpful in emphasizing the importance of identifying scale problems. It is also helpful in protecting the resilience of critical ecosystems, as well as drawing attention to the importance of quickly implementing policies to solve scale problems.


Optimal Scale and Maximum Sustainable Scale

Conceptually, maximum sustainable scale and optimal scale are distinct (see Scale Categories).  Maximum sustainable scale is that conceptual level of economic throughput which is the borderline between sustainable and unsustainable activities.  It is the point beyond which carrying capacity is exceeded, or overshoot occurs.  Because of the complex and dynamic nature of ecosystem functioning, we do not have the knowledge to describe it empirically with any precision.  


Optimal scale is that level of economic throughput which is within the sustainable range, and which establishes a safety margin within this boundary.  Optimal scale is our policy priority because of the safety it provides, ensuring that our economic throughput remains sustainable and does not inadvertently exceed the sustainability threshold.


These two scale benchmarks coincide when the critical ecosystem affected by some compound has zero absorptive capacity for that compound.  In other words, when a compound cannot be absorbed or broken down by natural ecosystem functions, there is no tolerance for the compound.  Any level then pushes the ecosystem to an unsustainable level of functioning. This insight reinforces the lessons concerning the importance of preventing scale problems from occurring in the first place, the importance of developing a scale relevant protocol to test new compounds, and the importance of accepting and enforcing a total ban on any compounds that challenge critical ecosystem functioning.


Ensuring Compliance

Each of the above scale lessons from the atmospheric ozone story emphasizes the importance of a complete ban on ozone depleting compounds to avoid further destruction of the protective layer.  The Montreal Protocol involves the gradual implementation of a total ban.  But there are problems.  Illegal manufacture of ozone depleting compounds continues, and old supplies are still being sold on the black market.  In addition, some countries are asking for exemptions for substances that are on the banned list.


The Montreal Protocol itself is flawed in terms of its lack of attention to new ozone depleting compounds, the rapidity with which reductions and eventual banning are scheduled to come into effect, the lack of involvement of some nations, and the lack of enforcement mechanisms.  The relative success of the Protocol in first of all obtaining an agreement, and in then actually reducing emissions of ozone depleting compounds, may be one reason for downplaying what could appear to be minor problems from the perspective of international negotiations. Compared to most such negotiations, it has been a remarkable success.  Compared to the need for a complete and total ban to avoid exceeding sustainable scale, much work remains to achieve sustainable scale.


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