Predicting Our Ecological Future Via Computer Scenarios

Authors Donella Meadows, Jorgen Randers and Dennis Meadows created a sophisticated computer model of ecological scenarios of the world called World 3. In these scenarios, they depicted various human interactions with the environment based on a number of assumptions related to sustainability and ran the models to obtain a forecast of possible results. These models were understood to be somewhat variable and not objective in an absolute sense but could point towards trends of what would be likely to occur given a known input. After running thousands of scenarios, the researchers found that the majority of the experiments resulted in overshoot and collapse. Overshoot is defined here as exploiting natural resources beyond sustainable levels. It is currently thought that humanity is 20% or more in overshoot presently and that we have little time left to correct our exploitive endeavors before substantial societal collapse is inevitable. I will give a brief synopsis of the six primary scenarios.

Scenario one. This first scenario is a reference point. It asserts that things will continue to go on as they have in the past and that overshoot and collapse will inevitably result. Accessing non-renewable resources will become increasingly more expensive and dealing with increasing pollution will be very difficult. Thus, industrial output and food production will peak in a few years and will be in substantial decline by 2030. Population growth will also follow this peak and decline pattern closely

Scenario two. Optimistic assumptions: non-renewable resources including fossil fuels will somehow double quickly. Technology will be able to cope with the cost of diminishing resources as they do occur. The population and economic production will continue to increase exponentially such that global pollution of soil, air and water peak at a level five times the level indicated in scenario one. At this time, there will develop substantial disruptions in the food supply and health issues will become critical. Industrial output and population growth will both reach a peak in the year 2040 and collapse will predominate from then on.

Scenario three. Humanity takes sustainability seriously and commits to reducing pollution at a 4% decrease per year for many decades. (This figure is well beyond what is being considered currently as a viable reduction percentage). Society still overshoots and collapses.

Collapse occurs because of the amount of money needed to address intense pollution and to provide enough food for the quickly growing population. Massive soil erosion and depletion exceeds the ability of the industrial base to procure adequate capital to rectify this condition. Again, a peak is realized at about the year 2040 and then declines rapidly thereafter.

Scenario four. This scenario adds yet another positive attribute to scenarios two and three. Humanity is now able to procure an adequate food supply via technological breakthroughs in increasing food yields per acre thus countering one of the biggest problems of sustainability. Despite these helpful developments, the model still overshoots and collapses. The intensified agricultural process causes increased soil erosion and degradation and more land is needed for settlement due to the ever-increasing population growth. Eventually it becomes too expensive to provide enough food and other diminishing natural resources also deplete remaining capital. A collapse of eminent proportions is realized by 2100.

Scenarios five-through-eight. These scenarios attempt to add more optimistic assumptions into the equation but the model invariably overshoots and collapses. What can be derived from these models is that humanity has to deal with a whole series of limitations (soil, water, air, climate, renewable and non-renewable resources) and because all systems are connected, it is hard to predict just how our actions will impact on our habitat.

Humanity has not learned how to or has not attempted to seriously address the issues of economic and population growth. Continuing to use the Earth’s natural resources at our current rate without the understanding that the Earth is a closed system will inevitably lead to overshoot and the collapse of all human societies.

Reliance on free markets and technology alone will not provide for a sustainable future. They are certainly a part of the solution but they are simply not enough. Our insatiable desire for unlimited growth will ultimately lead to societal failure.

Scenario nine: sustainability. In this model are included the assumptions that would result in a sustainable society. The assumptions are as follows:

1. Population growth worldwide would recede to the average replacement level of 2.1 children per couple and remain there, allowing the population to further increase to 8 billion and then stabilize at that level. 

2. All global economic activity would be thoughtfully planned by governments, leaders and individual business owners to produce an economy with a no-growth or decline rate.

3. Renewable resources are used at a sustainable level or at a rate no greater than they can be replaced. This includes every aspect of the biosphere (all flora, fauna, water, soil, air, and climate).

4. Nonrenewable resources are utilized at a rate no greater than they are being replaced by renewable alternatives (fossil fuels will not be used faster than alternative energy sources can be developed and activated to replace them).

5.  Pollutants are emitted at a rate no greater than the rate at which the Earth’s sinks including the forests, soils, oceans, atmosphere, etc., can absorb the pollutants and render them harmless.

Note that all of these assumptions must be working simultaneously for a society to become sustainable and flourish. The Earth is a closed system and we must learn to live within its acceptable parameters. It is also notable that this model did not include wars, major natural disasters, epidemic diseases, ethnic strife, corruption, or nuclear accidents. Thus, it could be viewed as quite optimistic. If this model were implemented in a delayed mode of say 20 years, collapse would inevitably occur. We no longer have the luxury of mulling over what we should do and when to start. We are already way behind schedule to act and the clock is ticking.


A Global Vision: General Principles for a Sustainable Planet.Jim Sloman, 2008, Oceanblue Publishing, 40 Fourth Street, Petaluma, CA  94952, pp. 133-136. Accessed 10 June 2020.

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