by Elizabeth Sawin

— September 2, 2004 —

Pick up the newspaper on any day and you are likely to find plenty of bad news about humanity’s impact on the Earth. From the global to the regional to the local, if you are feeling pessimistic you can find all sorts of “proof” that humanity is well on the way to self-destruction.

If you keep looking, beyond the bad news you will find good news as well – although usually not on the front page. Some fisheries are being managed sustainably and have been for decades. Production of organic food is rising. The ozone layer is stabilizing. Communities are preserving land and building bike paths and setting their own greenhouse gas emission goals. New technologies and the evolution of old ones could make feeding, transporting, sheltering, and cleaning up after ourselves much more efficient. Based on all this good news, an optimist might say that all we need is more of the same to glide in to a secure future.

It can be tempting to try to figure who’s right – the optimists or the pessimists. But that whole question can also be a distraction, like trying to puzzle out whether the boat you are paddling through rushing water is doomed or safe instead of concentrating on reading the current and paddling with as much power and sense of direction as you can muster.

If you’re willing to leave the pessimists and the optimists to their arguments and instead are looking for a guide to paddling our particular river, our moment in time with it’s mixture of troubling trends and hopeful developments, then seek out the newly published, thirty year update to Limits to Growth, a book first published in 1972. (Limits to Growth – The 30 Year Update by Donella Meadows, Jorgen Randers and Dennis Meadows, published by Chelsea Green Publishing Company). It won’t settle the argument between the pessimists and the optimists, but it does help explain how our global society has ended up beyond the carrying capacity of the Earth’s systems and what it will take to ease down below the limits.

The book reports on the lessons from a computer simulation model first built by the authors and other young researchers at MIT in the early 1970s when they were trying to understand the dynamics of a growing human society’s approach to the carrying capacity of the planet. Why and how was the system approaching the carrying capacity in the first place? And what sort of outcomes might be expected if society did in fact reach or exceed some of those limits?

To build their model the researchers made four critical assumptions, descriptions of which I have copied from an unpublished piece Donella Meadows wrote about the modeling work:

• Growth is inherent to the present human value system, and growth of both the population and the economy, when it does occur, is exponential.

• There are physical limits to the planetary sources of materials and energy that sustain the human population and economy, and there are limits to the planetary sinks that absorb the waste products of human activity.

• The growing population and economy receive signals about physical limits that are distorted and delayed. The human response to those signals is also delayed.

• The planetary limits are not only finite, but erodable when they are overstressed or overused.

These four assumptions are enough to produce, in the simulated computer “world,” the same patterns of behavior that we see in our real world, patterns to which we tend to gives labels such as climate change, or Gulf Hypoxia, or fishery crashes.

In the model runs presented in the book (which are updated from the 1970s version), without anyone “intending it,” the growing population and economy drain down resources and produce wastes at a growing rate. Because the consequences of these falling resources and rising wastes don’t immediately influence the growth rate of the population/economy system, that system continues to grow and “overshoots” the limit, just as has happened for CO2 in the atmosphere, nitrogen in the Gulf of Mexico, cod fishing in Georgia’s Bank, and dozens of other examples.

The authors report on what it takes in their simulated world to recover from overshoot and avoid collapse – a combination of constraints on growth and adoption of more efficient technologies, and they suggest the kinds of work this will require in the real world, including:

• Extend the planning horizon

• Improve the signals

• Speed up response time

• Minimize the use of non-renewable resources

• Prevent the erosion of renewable resources

• Use all resources with maximum efficiency

• Slow and eventually stop exponential growth of population and physical capital.

There’s much more in the book of course – useful data and clear graphics, and, in the final chapter, thoughts about the attitude and skills it will take to pull off the work of easing down below the limits. These features are reason enough to read the book, but there is another, more important reason, as well.

For the thirty years that this book and others with similar messages have been in existence the world’s leaders have been slow to acknowledge limits to growth and slow to take action based on those limits. That puts the burden of learning from Limits to Growth back on the rest of us. If the idea that we have overshot the limits and must now ease down from them fits with your experience of the world, then read the book, take from it what you can, and put it to use, in your life, your conversations, and your strategizing for the future.

© Sustainability Institute