Title: Limits to Growth – The 30 Year Update
Authors: Donella Meadows, Jorgen Randers and Dennis Meadows
Published: 2004

Overview: The book presents a complete 30-year update of the original whole-earth system modeling work conducted originally at MIT’s Sloan School of Management. The analysis supporting the original work, Limits to Growth (“LTG”), was conducted over a two-year period by an international team of scientists and was commissioned by the Club of Rome, an informal but distinguished group of international business executives, scientists and statesmen. The original work was the first widely supported whole-earth comprehensive systems study of mankind’s current living patterns and sustainability. While necessarily high-level or imprecise in many projections, LTG still held a generation-long influence over leading earth scientists and developmental economists.

The present work is based on their updated model W3-03 which is run for a variety of scenarios. As in the original LTG, upon reviewing the results the authors plead for “profound proactive, societal innovation through technological, cultural, and institutional change in order to avoid [any further] increase in the ecological footprint of humanity beyond the carrying capacity of planet Earth.” In a word, we have already overpopulated and over-consumed the earth’s long-term capacity to support our present and projected living demands.

Detail: The new book begins by presenting the work of Mathis Wackernagel and his colleagues, which measures the ecological footprint of humanity and compares it to the earth’s “carrying capacity”. Sometime in the 1980s, humanity’s ecological footprint surpassed the earth’s carrying capacity and now exceeds it by approximately 20%. Moreover, this significant over-consumption, on a per capita basis, is driven disproportionately by developed economies. If standards of living of the earth’s poor were shifted in any material way towards parity with the earth’s relatively rich, the over-consumption would be vast and devastating. When the earth’s limited carrying capacity is considered, growth alone can not be counted on as the panacea for the earth’s poor (sorry, Jeff Sachs).

To help explain the insight that derives from this modeling, the authors go to some length to explain the mechanics of feedback loops, and the overshooting and collapse that are included in or revealed through the observation of feedback loops by W3-03. Perhaps somewhat underappreciated is that the driving force behind our current dilemma is the recent exponential growth of the population as well as of energy and resource consumption. Even though population growth rates are declining in most developed countries, those in the larger underdeveloped part of the world are still powerfully active.

Our consumption of goods and energies obviously draws from the resources of the earth’s crust. But perhaps not so obviously, all goods and energies have both production and post-use refuse and by-products which must be stored in the earth’s sinks. The authors find four significant resources that have not managed to achieve sustainability, (1) arable (cultivatable) land, (2) potable (drinkable) and agricultural water, (3) renewable forests, and (4) oceanic fisheries. Consider these single data points: (1) topsoil is being lost at rates that are 16 to 300 times faster than it can be replaced, (2) throughout the 20th century, the growth in ground water withdrawal has been approximately twice as fast as the population growth, due mainly to the hydrologic expense of raising livestock, (3) between 1990 and 2000 more than 375 million acres of natural tropical forests (an area equal to that of Mexico) have been converted to other uses.

We live in a vast interdependent web. Yet our ecological footprint activity is wreaking havoc with the diversity of species, with 24% of the world’s 4,700 mammals now at risk of extinction, 30% of the 25,000 fish species at risk and 12% of the 10,000 bird species at risk.

To scale the impact of our consumptive lifestyle, the authors suggest that every ton of post-consumer garbage already produced 5 tons of waste during manufacturing and 20 tons of waste during initial resource extraction.

The authors conclude from their work that there is a critically imminent need to address our excessive ecological footprint. In traditional systems analysis, the longer the lead time in a feedback loop, the more likely the overshoot and the more pernicious the collapse. Accordingly, the authors urge immediate action along a portfolio of critical paths to shorten the feedback loops and hopefully limit the amount of further damage.

Three Points of Personal Interest:

1. As measured between 1960 and 1995, the distribution of income worldwide between the poorest 20% and the richest 20% has grown from 30:1 to 82:1.

2. About 50 million acres of tropical forests are being cleared each year now. At this rate there will be no primary forests on the earth in 95 years.

3. An average North American uses 900% more energy than an average Indian.