The Parable of the Yeast, a Story about Economics and Sustainability

Once upon a time there was a student with a packet of yeast, a box of sugar, and an Erlenmeyer flask. The student was instructed to put the package of yeast into the flask, add a measured amount of sugar, fill it up with water, top with a balloon, and put the whole thing in a warm incubator. The student was instructed to observe and measure, writing down numbers in a notebook, and then to make sense of the results.

The student (a naïve young thing who had never made bread) was amazed to observe the whole concoction get cloudy and bubbly. The balloon expanded with gas. In a few days, the liquid cleared, leaving a scummy mess on the inner surfaces of the flask.

Now imagine that our student actually had been instructed to make up several flasks, with varying amounts of sugar or different temperatures, and to take measurements each day. The student counted the yeast, measured the amount of sugar, and sampled the gas in the balloon. The student measured specific gravity and dipped a piece of pH paper into the liquid. The student discovered that sugar was necessary for the yeast to grow and that the gas was carbon dioxide. The student found that there is an optimal temperature for the growth of yeast and that yeast consumes the sugar and generates alcohol and CO2. And the student found that when the liquid cleared up, the yeast colony had died.

Our student, if she is a good student, has learned some important biological principles and hopefully did well on her assignment. Her teacher probably extended the lesson to help the student draw some conclusions about the importance of environment – about how food is a limiting factor and how waste products, like alcohol and CO2, poison the environment.  But she likely learned nothing about how this experiment relates to human societies because biologists don’t teach about economics (and economists don’t teach about biology).

Not only do economists not teach their students about biology, most (but not all) don’t believe biology has anything to teach them about economics. Mainstream U.S. economic theory posits that human growth cannot be limited by scarcity or toxicity because we are so smart that we will be able to invent, engineer, or bioengineer our way out of any problem. Not only that, but they believe the market is self-correcting and when resources get scarce, prices will go up and people will find substitutes. What the economists forgot to consider were two important facts:  resources are in fact limited and we can outstrip our ability to manage certain waste products.

Our planet looks a bit like the yeast colony today. More and more people are starving and the amount of CO2 has gotten to a critical level which is wreaking havoc on our climate, mucking up the ideal conditions for human life on this planet.

What does the parable of the yeast say to us about sustainability? The basic definition of sustainability is living today in such a way as to not compromise the ability of future generations to exist. Sustainability is popularly pictured as a three legged stool or a Venn diagram with a balance between economics, society, and environment. The parable of the yeast suggests that sustainability is a nested set of conditions, with economics serving the society which exists within the environment.

My thinking was stimulated by an essay entitled “Bigger Isn’t Better,” by Peter A. Victor, an economist at York University in Canada. 

Dr. Victor says “Ecological economists understand economies to be subsystems of the earth ecosystem, sustained by a flow of materials and energy from and back to the larger system in which they are embedded. It is understandable that when these flows were small relative to the earth they could be ignored, as they have been in much of mainstream economics. Economists are not alone in treating the economy as a self-contained, free standing system largely independent of its environmental setting. It is a widely held view that environmental protection is just one among multiple competing interests to be traded off against the economy.

“And anyway, this mainstream perspective teaches that if resource and environmental constraints are encountered, scarcities will be signaled by increases in prices that will induce a variety of beneficial changes in behaviour and technology. Should this system of scarcity-price-response fail then economists can estimate “shadow” prices which can be imposed directly through taxes or used indirectly through policies based on cost-benefit analysis to fix the problem.

“To ecological economists, this is an inadequate response to the myriad problems of resource depletion, environmental contamination and habitat destruction confronting humanity in the 21st century. They question the pursuit of endless economic growth and contemplate a very different kind of future.”

If the paradigm of the economy equals growth is failing us today, is the solution to change the paradigm to one in which the economy equals sustainability? If we want to learn from the Parable of the Yeast, the answer must be yes.

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