What is sustainability?

Till now man has been up against Nature; from now on he will be up against his own nature.  ~Dennis Gabor, Inventing the Future, 1964

I became interested in the idea of sustainability early in the 1970’s when I was in junior high school. I distinctly remember reading a book called “Future Shock” by Alvin Tofler. I can’t find a copy of the book today, but my recollection is that it described the huge amount of waste that our society produces. The book took the Malthusian approach, named after Thomas Malthus, who in 1798 published a paper titled “An Essay on the Principle of Population”. Malthus argues that agricultural production would limit human population growth. Unchecked population growth could lead to a “Malthusian catastrophe” in which widespread starvation would reduce the population to a level that could be supported at a subsistence level. This bleak view of the future was later supported by studies of animal populations. For example, at times when food is abundant, deer populations increase at an exponential rate, but when food is scarce for extended periods of time (due to drought, extended winters, etc.) deer will die in large numbers, and the deer population plummets. This cycle repeats indefinitely, and widespread recognition of this problem is the justification for the culling of deer populations by hunters. The Malthusian concept has more recently been extended to all resources that are essential for maintaining our current lifestyle, including metals and oil, and people who subscribe to this view are labeled “neo-Malthusians”.

I think all of us have seen the Malthusian concept in action. For example, in my laboratory I have succulent plants in two pots that I purchased about ten years ago. If you take good care of plants, they grow over time, and their pots must be replaced with bigger pots to accommodate the growth. Humanity’s pot is the earth, and unfortunately it is fixed in size. Being lazy when it comes to plant care, I never changed the pot, so the plants were very healthy while growing then reached the limits of growth and partly withered. Branches fell off and died, and now the plants seem to have reached a steady-state where their growth is not prodigious and the existing branches appear a little less healthy. This is analogous to the Malthusian catastrophe: once the sustainability limit is reached (in this analogy the limit is set by the amount of root that can fit in the pot), there is a die-off and the human population (or in this case plant mass) decreases, and then continues at a subsistence level thereafter. Cornucopianists argue that we can grow the pot, but notice that for plant growth to resume we must grow not only the pot but also the amount of soil, water, and fertilizer. Any one of these essential components could limit growth; unlimited plant growth can occur only if there is unlimited growth in the availability of these critical resources. Can humans grow the supply of every resource that we need, indefinitely?

The Malthusian view is generally supported by scientists, particularly ecologists who see it at work in ecosystems as described above. The opposing view is espoused by “cornucopianists”, who contend that Malthusian limits do not apply to human populations because our intelligence can overcome those limits. Cornucopianists can be considered optimists because they believe there are no limits to growth, while Malthusians are more pessimistic. The debate between Malthusians and Cornucopianists is embodied in the bet that scientist Paul Ehrlich made with economist Julian Simon in 1980. Ehrlich posited that population growth would increase demand on a limited supply of metals, causing the price of those metals to increase in one decade. Simon won the bet because the price of all five metals decreased. However, Simon lost a less-known wager that he made with David South of the Auburn school of Forestry in 1995. Simon wrongly bet that timber prices would decrease in five years. Of course, as a scientist I believe that economists like Simon are wrong, and to support my view I simply point out that economists’ predictions about the future are more often wrong than not; witness the economic collapse of 2008 that was completely unanticipated. As pointed out by the biologist E.O. Wilson in his brilliant book “Consilience”, economics is not a science because it has essentially no predictive power.

Malthus has been buried many times, and Malthusian scarcity with him.  But as Garrett Hardin remarked, anyone who has to be reburied so often cannot be entirely dead.  ~Herman E. Daly, Steady-State Economics, 1977

*Mention Club of Rome study “Limits to Growth”

Sustainability refers to the long-term ability to maintain an ecosystem or human society. In this book we will primarily discuss the sustainability of human societies because that is what the reader is most familiar with. However, I would argue that we cannot maintain human society without also preserving our supporting ecosystems and their biological diversity, because we depend on those ecosystems to provide our food, water, air, and medicines. In short, ecosystems provide many life-support functions that we take for granted, but we must always remember that without those ecosystems we would likely perish. Fortunately, most of the solutions I prescribe for preserving human society also help to preserve our supporting ecosystems.

Important components of sustainability are illustrated in the figure Three_spheres.jpg. As shown in the figure, the three pillars of sustainability are Social, Economic, and Environmental (or the equivalent three P’s: People, Prosperity, and the Planet). As we’ll discuss below, our human population continues to increase at an exponential rate, which requires us to accommodate that growth in our temporary plans. However, we must remember that exponential rates of change of any kind are unsustainable and lead to unstable systems. To provide for growth in a sustainable fashion we most engage in sustainable development, which will allow us to "leave future generations the capacity to live as well as we do today" (Robert Solow).

One of the main messages of this book is that our society will experience resource shortages in the near future. Some resources will become of short supply within the lifetimes of my generation (baby-boomers). Others will become scarce during the lifetimes of our children. To understand this problem, we must introduce some terms and concepts. Renewable resources can be created, whereas non-renewable resources either can’t be created or are created at such a low rate that we essentially have a fixed supply of them. Non-renewable resources are fixed in quantity, so the faster you use them, the faster they run out. Fossil fuels fall into this category because it takes millions of years for nature to produce oil and coal from plants. In general, we are more at risk of running out of non-renewable resources. However, we can also run out of renewable resources if we use them much faster than they are replaced. For example, marine fisheries are collapsing worldwide because over-fishing has decreased the populations of certain fish species to critically low levels; those fish species may become extinct, or if left alone to breed they may regenerate their populations to preexisting levels, but that could take many decades. You may have noticed that certain species of fish such as haddock have essentially disappeared from grocery shelves; this is because the commercial catch of haddock has declined rapidly in recent years, and its conservation status is now considered “vulnerable” (http://en.wikipedia.org/wiki/Haddock). The figure resource_availability shows how the amount of a resource can grow or shrink, depending on the relative rates of replenishment (input) and extraction (output). Our haddock example is of type (b), where we the rate of extraction exceeds the rate of replenishment. Resources that fall in this category are the ones we must be concerned about, and we will examine many examples, particularly water. In case (a), the rate of input equals the rate of output, and we have what’s called a steady-state in which the amount of resource available for use remains constant. Steady-state systems are stable because they don’t change, and the optimal use of renewable resources is to maintain them at a steady state. The sustainable approach to managing renewable resources is to harvest the resource at the same rate they are produced. Sustainable use of renewable resources is desirable because it guarantees long-term availability of those resources.


About johncayers

John C. Ayers is a Professor of Earth and Environmental Sciences at Vanderbilt University. As a geochemist he specializes in sustainability and also the chemistry of natural waters. He has been PI on 5 and co-Pi on 2 grants from the National Science Foundation, and has a publication h-index of 14. He has been Associate editor of American Mineralogist and Geochemical Transactions of the American Chemical Society, and does GIS consulting for the ERS group. He is currently writing a book titled " Sustainability: The Problems of Peak Oil, Global Climate Change, and Environmental Degradation."
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