Time is Short

Sustainable Scale Already Exceeded
Many scientists believe that sustainable scale has already been exceeded in several critical areas. Use of non-renewable resources is by definition not sustainable. As we increase our use of such resources without planning for replacement of the unique benefits they provide, we deprive future generations. Petroleum is a good example (see Energy). The accelerated rate of biodiversity loss (see Biodiversity) is many times the preindustrial level. The increasing loss of KEYSTONE SPECIES means this loss will continue to get worse. We have exceeded the sustainable scale of various fisheries. These resources should be newable. Our emissions of novel man-made toxic substances, for which ecosystems have little, or no, tolerance is increasing (see Toxic Substances). The production and emission of ozone depleting compounds into the atmosphere quickly exceeded sustainable scale (see Ozone). Concentrations of greenhouse gases are in excess of those in the preindustrial period by over 30 % (see Climate Change).

Effects of Exceeding Sustainable Scale
Exceeding sustainable scale means that we are living off natural capital rather than natural income (see Natural Capital and Income). This situation inevitably depletes natural capital, and if the depletion continues, natural capital will eventually be reduced to zero. The further beyond sustainable scale this depletion occurs, the more vulnerable are the multitude of ecosystem services provided by this fund of natural capital. And the longer the level of material throughput exceeds sustainable scale, likewise does vulnerability increase (see Scale Policy Implications). Exceeding sustainable scale therefore has two major effects:

• the quantity and quality of ecosystem services begin to decline
• the loss of ecosystem resilience gets worse as the duration and magnitude of exceeding scale continues.

Implications of Exceeding Sustainable Scale
Ecosystems are generally designed to be sustainable under a broad range of conditions, and can continue providing some level of services even beyond sustainable scale. But if pushed beyond this range by human activities, they react in unpredictable ways. For example, changes are not necessarily linear with respect to the levels of stress applied. A doubling of atmospheric greenhouse gas concentrations beyond preindustrial levels will have more than twice the impact of a 50% increase. At some level of continued disruption, an ecosystem will flip into a different equilibrium state, and may do so quite rapidly. The ecosystem’s natural resilience will assist in maintaining the old equilibrium, but as resilience declines, the likelihood of an equilibrium flip increases. Our knowledge of global ecosystems is totally inadequate to allow us to predict when such flips might occur. Therefore, the longer we exceed sustainable scale, the greater is the risk of reaching and exceeding maximum scale – the point of no return (see Unsustainable Scale).

Long Timelines
The biophysical mechanisms that determine ecosystem variability operate over timelines that are very long by human standards. Both greenhouse gases and ozone depleting compounds continue to be active for up to a century after they are emitted into the atmosphere. The greenhouse gases emitted a century ago are influencing current climate patterns. Those emitted today will continue influencing climate stability for another 50 years or more. Anthropogenic ozone depleting compounds began acting almost immediately to upset the natural balance of atmospheric ozone creation and depletion, and those emitted today will continue their impact for a century or more. What we do over the next few years will have a long term impact on global ecosystems. The sooner we act to preserve and restore natural capital, rather than depleting it, the more we will enjoy the benefits of the associated ecosystem services, and the less we will have the time pressures of dwindling services and impending catastrophe. We are both richer and safer if we remain within the range of sustainable scale.

Short Timelines
Ecosystems generally operate on timelines beyond the range of direct human experience. But They can change from one equilibrium state to another very rapidly. As material throughput increases exponentially, reducing doubling times (see Exponential Increases in Throughput in Excess Throughput), we may be misled to believe we have considerable time to remedy our ecological errors. We are relatively ignorant regarding the point at which the next doubling will push an ecosystem beyond sustainable scale. Not knowing just how short such a timeline might be suggests extreme caution in avoiding unsustainable scale.