Levels of Unsustainable Scale There are also many levels of unsustainable scale, ranging from a level where throughput is only slightly higher than regeneration, to a level where throughput exhausts or destroys the ecosystem’s capacity to regenerate, where resilience is exhausted. Obviously, these different levels of unsustainable scale represent different levels of threats to the well being of humans and other species. Unsustainable levels of throughput that are only slightly higher than maximum sustainable scale (see above) are less dangerous than levels of throughput which greatly exceed the rate of regeneration. If the level of throughput is so much higher than the rate of regeneration that it overwhelms the ecosystem’s capacity to continue functioning, the basic ecosystem dynamic is changed and a new equilibrium established, then Maximum Scale is exceeded. The concept of maximum scale represents the point of no return, the level of throughput where the ecosystem functions upon which we depend, are no longer available. Maximum scale is defined by the biophysical limits of affected ecosystems. Such a level of throughput may be difficult to identify empirically with precision; the concept nonetheless serves as a useful reminder of the inevitable consequences of too much throughput relative to what ecosystems can process.
An Invisible Threshold The shift in the global economy from a sustainable to an unsustainable scale of material throughput was hidden from view and daily experience. The same amount of benefits from nature (e.g.timber, fish, biodiversity, etc) could be experienced even after this threshold was crossed. The difference was that once we passed maximum sustainable scale, the benefits were being derived from a drawdown of natural capital, rather than the annual renewals of natural income. Our lack of a natural capital accounting system meant we could not distinguish this silent shift. Because the capital fund was so large relative to the demands made on it, we could enjoy the same drawdown without realizing a threshold had been crossed.
The Inexorable Slide However invisible, once sustainable scale was exceeded, our growing levels of material throughput (and their increasing toxicity) meant we were on an ever more rapid slide toward a catastrophic point of no return. Once sustainable scale is exceeded, it is just a matter of time before ecosystems are degraded to the point where they can no longer generate life support benefits. The fact that our levels of material throughput continue to grow means we will reach this catastrophic state that much sooner.
Ecosystem Resilience Buys Time… Ecosystems have the remarkable capacity to regenerate themselves if left undisturbed. A forest that burns from a lightening strike will eventually grow back; over-fished stock will regenerate if sufficient numbers remain and their habitat is intact. This characteristic resilience of ecosystems means that the inexorable slide toward a catastrophic point of no return can be slowed and reversed, bringing the level of material throughput causing the degradation back to a sustainable level.
But Not Forever… Ecosystem resilience also has its limits. Resilience operates over the entire range of throughput levels, but the more material throughput that must be dealt with, the more difficult it is for the mechanisms of resilience to regenerate natural capital. Resilience declines when sustainable scale is exceeded; the higher the level and duration of throughput within the unsustainable range, the weaker resilience becomes.
When biophysical limits are reached irrevocable losses will occur and resilience will be extinguished.
Dynamics of Unsustainable Scale The dynamics of unsustainable scale include the following:
- Within the unsustainable range, the lower the level of economically driven material throughput the less the degradation to ecosystem functions (i.e. the easier it is for ecosystem resilience [glossary term] to restore function)
- Within the unsustainable range, the higher the level of material throughput the greater the degradation to ecosystem functions (the higher the level of throughput the less likely is resilience to restore functioning)
- Within the unsustainable range, regardless of the level of material throughput, the longer throughput remains unsustainable, the greater the degradation to ecosystem functions (the longer unsustainable throughput endures the more resilience is weakened)
- Within the unsustainable range, regardless of the level of material throughput, if the throughput endures long enough, the capacity of affected ecosystems to continue functioning will eventually be destroyed (i.e. resilience will be exhausted and maximum scale will be exceeded) and a new equilibrium will be established
- Within the unsustainable range, the relationship between the level of material throughput and the level of ecosystem degradation is non-linear; small increases in the amount, or duration, of unsustainable throughput can result in high levels of degradation to ecosystem functioning.