Toward a stewardship of the Global Commons:

engaging “my neighbor” in the issue of sustainability

By members of the Critical Issues Committee, Geological Society of America

Part IV


E-an Zen, University of Maryland, College Park, MD


Whenever we ponder the future of the human enterprise, questions about material resources come up.  Will they run out?  Will they replenish themselves?  Will the demand for them diminish, or will alternatives be found?  Without a good estimate of those resources, we will never be able to predict or improve human welfare.  "Malthusians" have a doomsday outlook; "Cornucopians", a more optimistic view (McCabe, 1998).  Yet whichever school of thought seems more persuasive, the fact remains that we live in a materially closed system.  The Earth's resources are finite, so we must choose how best to use them.


A society needs reliable information on the resources available to it and on the consequences of their use.  How it will act on that information will depend on its value system.  For example, a society may place a high priority on fair distribution of wealth.  We in the developed nations have an opportunity to demonstrate a commitment to use resources in a sustainable way.  Do we want to act responsibly toward future generations of our species and toward other life forms as well? 

Material resources are whatever the society at a given moment either uses or recognizes as potentially usable.  Because that list changes with society's needs and technology, what is useless one day may become vital the next.  As recently as a century ago, aluminum, petroleum, and uranium were not significant resources. 


Geologists tend to think of "resources" as the stuff we take from the ground: metal ores, coal, petroleum, groundwater, limestone, phosphate, quartz sand and rock.  The earth's resources, however, also include living things that are subject to human exploitation. 


Trying to inventory resources for the future, thus, is like aiming at a moving target.  Yet some statements will remain valid for three reasons: (1) except for energy input from the sun, which supports and maintains our “ecosystem services”, the earth is a closed system having a fixed quantity of materials.  (2) Both the extraction and processing of materials and preservation of the environment require energy, itself a resource.  (3) Using a material generally changes its state of aggregation, and its adaptability for future use.  Thus, the processing of materials, including recycling or re-aggregating waste material into usable form, causes a thermodynamically inexorable loss of useful energy and/or material.  With regard to Earth’s material resources, there is no free lunch! 


To these factors must be added both an increasing global population (projected to reach about 9 billion people by 2050), and a higher per capita consumption rate reflecting  "improved" standards of living.  Obviously, resource considerations are crucial for the success of the human enterprise.

Traditionally, resources are grouped as "nonrenewable" and "renewable".  Nonrenewable resources (examples: ores, petroleum, coal) replenish at geological rates that are much too slow to benefit human society.  Once consumed, such finite resources are effectively removed from our inventory.  New discoveries or more efficient extraction methods merely postpone their inevitable exhaustion. 


"Renewable" resources (examples: timber, fishstock, groundwater) have rates of natural replenishment commensurate with the time- scales of human society (see DEMONSTRATION 1 below).  However, to consume such resources faster than they can replenish themselves is like withdrawing funds from a bank account faster than we make deposits; sooner or later that account will run out.  We have often been guilty of just such overwithdrawal.  Examples include overfishing, poor husbandry of arable and pasturable land, overpumping of aquifers, destruction of entire ecosystems such as Russia's Aral Sea.  Such "local" losses can have large systemic effects (see DEMONSTRATION 2 below).


More effective use of substitutes, recycling, and conservation can slow down depletion of a renewable resource (i.e., the amount of consumption that exceeds its renewal by all processes, natural or engineered), but they cannot halt the process.  To make a "renewable" resource truly renewable, the rate of consumption must not exceed the gross rate of renewal.  Reaching a "sustainable world" will demand many changes to our priorities regarding resource utilization.

Some vital resources, such as the "environment", are not material objects.  A healthy environment is a composite of many other items (e.g., water chemistry and temperature, nutrients and other chemicals in the soil, good habitats for wildlife).  A natural place of beauty and wonder is an intangible but valuable resource.  A less obvious intangible resource is the future generation's options, i.e., their capability to make real choices.  Options are not fixed commodities, but surely they will be important for future societies.  Like the options available to us today, many future options require the availability of material and energy.  Even if an earth material is not dispersed through use, their very processing automatically reduces future options of their use.

The results of human exploitation of resources cannot be predicted by looking at one commodity or one social force at a time.  Calculation of the effects of use and depletion of materials on the public commons (see Part I) must also include human values and cultural habits.  Justus von Liebig, a 19th century agricultural chemist, recognized the complexities that arise in a situation where humans and natural forces work interactively.  Historian Elliott West put von Liebig's view this way: "an organism's limits are set, not by the maximum profusion of necessary things, but by those things' minimum availability.. Look .. for how much is available when vital supplies are the tightest, lowest, stingiest". 


What is true for an organism is true for ecosystems.  Can we identify the "vital supplies", their mutual relations and their future trends?  Can we recognize the factors of "minimum availability" while there is yet time?  Or will they surprise us and perhaps blindside us?  Surely we need to be thinking about these issues.


To maintain a society's standard of living requires consumption of resources at some level.  In Part XX of this series, we will explore this subject within the "sustainability" context.


The author thanks Christine Turner of the US Geological Survey, Denver, for her contribution to the ideas and her critique of the text.



(1) Ask your students to list the resources that they encounter in one day of their activities, using the following categories:

A. "Nonrenewable" resources are those that may be replenished only at

     rates much exceeding the human time scale: for example, fossil fuel

     (what should be included here?), metals (where do they come from?).

B. "Renewable" resources are those that may be replenished on a human

     time scale, but only if the rate of withdrawal or destruction does not

     exceed the rate of replenishment: for example, timber, fishstock, soil,

     groundwater, environmental quality, mixed forests, ozone layer.


(2) Pick any material object: the gasoline you pump, a metal paper clip, the bricks of the building, the gravel in a driveway, a toothpaste tube, or a molded plastic chair.  For that object, ask the students to identify the resources embodied in it: where did the material come from, and in what original form?  Ask them to discuss what processes were needed to produce the object (e.g., mining, harvesting, refining, waste disposal, ecosystem disturbance, transportation, energy use).  What renewable or nonrenewable resources were used in the processing?  Are there substitutes that would require less energy and material?  How essential is this particular product to the students' comfort or well-being?  Could they make do with less?  What would be the tradeoff in making a more frugal choice?  Who might benefit from that choice, and in what way?



In a recent book, "Waiting for Aphrodite", Sue Hubbell, author-naturalist-apiarist, described recent stresses to communities of the green sea urchin, Strongylocentrotus droebachiensis, which lives off the rocky coast of Maine.  The population density of this sea urchin seems to go through cycles; in the 1980's they thrived.  Sea urchin eggs were a delicacy for the affluent Japanese.  When their local stock was becoming depleted at about this time, the Japanese merchants turned to Maine for a substitute.  Meanwhile, needing an alternative source of income because the coastal cod and haddock fishery had collapsed through overfishing, the fishermen of Maine started to dive for the green sea urchins.  Soon, however, the catch began to fall alarmingly.  Green sea urchin eggs are fertilized by sperm which last only a few minutes in seawater, so large congregations of urchins are essential for the species to survive.  Large congregations attract fishermen as well, but, luckily for the urchins, the Japanese yen weakened, the demand for pricey urchin eggs fell, and a Russian source became available.  Sea urchin "farming" is now being explored as a steady source of supply, so the natural communities of Maine sea urchins might yet recover. 


How might the disappearance of green sea urchins affect the ecology of the coastal waters?  We do not know.  Some years ago scientists thought that the long-spined black sea urchin, Diadema antillarum, of the Caribbean region was a useless species.  Then it was discovered that coral and sponge larvae can attach themselves to reefs only on surfaces kept clean by the sea urchins, which graze on the algae.  So the "useless" sea urchins turn out to be essential to the coral reef ecosystem, after all.


This particular story may be minor in the scale of things, but it provides a good example of the intricacies of an ecosystem.  If we act without adequate knowledge, we can easily throw an ecosystem out of balance, possibly irreversibly.



Hubbell, Sue, 1999, Waiting for Aphrodite: journey into the time before bones. 

Boston, Houghton and Mifflin.  242 p.

McCabe, P.J., 1998, Energy resources - cornucopia or empty barrel?  American

Association of Petroleum Geologists Bulletin, v. 82, p. 2110-2134.

von Liebig, Justus, 1847, Chemistry in its applications to agriculture and physiology:

London, Taylor and Walton.  418 p.

West, Elliott, 1998, The contested plains: Indians, goldseekers, and the rush to Colorado. 

University Press of Kansas.  422 p.

Return to Introduction
Guidelines to Sustainability Literacy
Part I: Stewardship of the Commons
Part II: Understanding Deep Time
Part III: Doubling Time

Part IV: Sustainability and Resources
Part V: The Connectedness of Everything
Part VI: Ecological Footprint and Carrying Capacity
Part VII: Spaceship Earth: There's No Place Left to Go
Part VIII: Part of the Global Ecosystem

Part IX: We Live in a World of Change
Part X: What Do We Mean by Sustainable World?
Part XI: Cultural Context of Sustainability
Part XII: We Have The Option of Choice

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