Our Ecological Crisis

Lecture III:  Our Ecological Crisis

Review

1. Energy flow through a typical ecosystem involves three distinct stages.  The system receives energy in the form of solar radiation, converts that energy into forms usable by its constituent organisms, and discharges the expended energy for disposal elsewhere in the biosphere.  An ecosystem remains stable as long as it receives enough energy to serve the needs of its top consumers and is able to expel the waste products generated within it.  These processes were elaborated in the previous lecture.
2. Similar processes are at work in the biosphere at large.  As we recall, the biosphere is the totality of organisms on earth along with the nonliving resources needed to sustain them.
    

   Figure 3.5:  Energy flows through the biosphere. From Kenneth Sayre, Unearthed: The Economic Roots of our Environmental Crisis. Used with permission.

   In this figure, the biosphere is represented by the outside circle.  This outer figure, we should note, is not the earth’s surface itself, but rather the layer of life located both below and above that surface.
3. The tightly variegated arrow entering from the left represents incoming solar radiation.  A major portion of this energy is taken up by nonliving (nonmetabolic) processes, like heating land surfaces and evaporating water.  The smaller section of the arrow headed upwards, on the other hand, represents energy put to work running the metabolisms of living systems.  For the most part, organisms expel the resulting entropy in the form of low-grade heat.
4. Entropy resulting from metabolic activity is represented by the upper branch of the loosely variegated arrow to the right.  The lower branch of this arrow, of course, is entropy resulting from nonmetabolic activity.  These two streams of entropy join to represent low-grade heat returning to space as black-body radiation.
5. Moving ahead, we should bear in mind that entropy from both metabolic and nonliving processes exits the biosphere in the form of low-grade heat.  Any impairment to the biosphere’s ability to discharge low-grade heat affects entropy stemming from both living and nonliving sources.  This is happening currently in the phenomenon known as global warming.

Global warming

1. Global warming is a concentration of low-grade heat in the atmosphere that the biosphere cannot discharge as black-body radiation.  It results in part from an impairment of the feedback mechanisms governing atmospheric temperature and in part from an excess of low-grade heat waiting to be discharged back into space.  Let us look at these causes first in isolation.
2. The feedback mechanisms suffering impairment involve the tendency of low lying (cumulus) clouds to reflect sunlight and that of higher (cirrus) clouds to absorb outgoing heat.  When expanses of earth beneath warm up, thermal convection encourages the formulation of more cumulus clouds, and more sunlight accordingly is reflected back into space.  As land cools, on the other hand, a larger portion of cirrus clouds result and more heat is retained in the atmosphere.  Other variables are involved, of course, but these are the main components of the atmosphere’s heat regulating mechanisms.
3. The presence of large amounts of CO2 in the atmosphere interacts with these negative feedback processes.  By itself, CO2 absorbs less heat than water vapor (e.g., in cirrus clouds), so that its effects are relatively minor over most parts of the light spectrum.  But there is one part of the spectrum (notably around 15 micrometers) where heat absorption by water vapor is minimal and that of CO2 becomes important.  This added boost by CO2 increases air temperature, which leads to more water vapor in the upper atmosphere.  This leads in turn to yet higher air temperatures, followed by higher concentrations of water vapor, and so forth.  As the positive feedback triggered by excesses of CO2 begins to override the negative feedback normally stabilizing earth’s atmospheric temperature, global warming sets in.
4. The other factor driving global warming is the increasing amounts of low-grade heat resulting from human industrial activity.  Simultaneously with the atmosphere becoming increasingly unable to get rid of its waste heat, we are producing increasing amounts of heat entropy for it to dispose of.  This is analogous to dumping more water into a flooded basement while the sump pump intended to drain it becomes increasingly dysfunctional.
5. There is no need to rehearse the consequences of global warming, which currently are a topic of worldwide debate.  Among disastrous outcomes expected within a matter of decades are costal flooding, widespread famine, and forced migration of human populations.

Ozone depletion

1. Another severe problem attracting recent attention is the disruption of the ozone layer in the upper atmosphere.  This shield of ozone blocks out ultraviolet radiation from the sun that is harmful to many forms of life.  Without this protection over the past billion or so years, human life as we know it could not have appeared.
2. Ozone (03) breaks down in the presence of chemicals like chorine and bromine.  A compound of chlorine called CFC (for chloroflourocarbon) was commercially developed in the 1930s, and in the subsequent decades found extensive use as a refrigerant (“Freon”) and spray-can propellant.  Signs of ozone depletion from escaped CFCs were detected in the late 1970s and brought to the attention of the world’s industrialized nations.
3. In 1987, these industrial powers convened to establish the famed Montreal Protocol, which banned the use of CFCs save in certain developing countries.  While this and subsequent treaties reduced industrial use of CFCs considerably, chlorine already in the atmosphere continued to work its mischief.  By the turn of the millennium, scientists were expressing cautious hope that the ozone layer would heal itself by the end of the present century.  Whether this happens will depend upon the success of international efforts to block release of further ozone-depleting chemicals into the atmosphere.
4. In the meanwhile, the human race will have to contend with increasing incidence of skin cancer, cataracts, and macular degeneration.  And the biosphere at large will have to cope with further destruction of plankton near the ocean surface and further damage to tender plants supporting terrestrial consumers.  Coupled with the dire effects of global warming, ozone depletion poses serious threats to continued human existence.

Functional disorder

1. Whereas global warming stems from a glut of entropy in the form of low-grade heat, ozone depletion is a case of functional disorder.  A point emphasized in the previous lecture is that functional disorder is also a form of entropy.  One example discussed previously is loss of species diversity.  With significantly fewer species in the biosphere, there are fewer pathways serving the function of channeling nutrients to its upper trophic levels.
2. Other functional interactions essential to ecological stability include (i) the ongoing interchange of O2 and CO2 between producers and consumers, (ii) the cycle of evaporation and condensation replenishing the earth’s supply of fresh water, and (iii) the nitrogen cycle providing nutrients to producer organisms.  These functions also are subject to disorder.  Let us take the nitrogen cycle as an example.
3. One phase of the nitrogen cycle is the conversion of free nitrogen to soluble compounds, called nitrification.  Among the main products of nitrification are ammonium (NH4) and nitrate (NO3) which plants assimilate as nutrients.  The other phase is the conversion of such compounds to gaseous form, called denitrification.  This occurs when nitrates from dead organic matter are broken down into nitrous oxide (N2O) and free nitrogen by bacterial action.
4. But N2O is a greenhouse gas.  Interrupting a natural balance between nitrification and denitrification in the biosphere, industrially produced fertilizer has resulted in millions of additional tons of gaseous nitrogen set loose in the atmosphere.  Industrial agriculture not only injects massive amounts of poisons into our soil and waterways; it accelerated the progress of global warming as well.

Nonbiodegradable wastes

1. Another form of entropy to mention before moving on is that of nonbiodegradable wastes.  Generally speaking, materials formed by biological processes are biodegradable.  This means that their chemical constituents are naturally recycled and that energy consumed in their formation can be released from the biosphere as low-grade heat.  Many artificially composed materials like plastics, on the other hand, do not decompose naturally.  Although they can be broken down physically into smaller and smaller pieces, those pieces remain in the biosphere indefinitely.
2. Most of us already know that very large quantities of discarded plastic products are being dumped into our oceans and landfills.  Included are myriads of plastic cups and bottles, zillions of plastic “peanuts” used (usually only once) for packing, and who knows how many disposable diapers.  What most of us perhaps do not realize is that small pieces of plastic have begun to enter the food chain.  In recent years an enormous mass of plastic debris has been caught in the North Pacific Gyre circulating off the coasts of California and Mexico.  Included are bits of plastic that resemble zooplankton and that are being ingested by jellyfish.  Tens of thousands of sea mammals die annually from the resulting “plastic poisoning,” which also has spread to water fowl in all the world’s oceans. 
3. Human industry has engendered entropy in the form of global warming, in the form of dysfunctional natural cycles, and in the form of nonbiodegradable wastes.  The biosphere has become impacted with this entropy to an extent that threatens the very existence of the species that produced it.  It is time to look more carefully at what has gone wrong.

Growing population and per capita consumption

1. To bring this predicament into perspective, let us piece together a brief history of human energy consumption.  This overview will be formulated in terms both of growing human population and of growing per capita energy use.  It will take us from the time of the so-called “hunter gatherers” to the beginning decade of the 21st century. 
2. During the hunter-gatherer era, population probably numbered around 4 million people.  Per capita energy consumption presumably was around 1 billion joules (one joule equals roughly ¼ calory) a year, the amount needed to sustain the world’s poorest people today.  Data and reasoning behind these and the following estimates are indicated in Ch. 6 of the text.
3. When foraging gave way to agriculture, more stable food sources resulted in a gradual growth both in population and in energy consumption.  Growth in per capita energy  consumption during this period is shown at the left of Figure 6.1.  Corresponding growth in population is shown in Figure 6.2.
    
   

   Figure 6.1:  Growth in per capita energy consumption. From Kenneth Sayre, Unearthed: The Economic Roots of our Environmental Crisis. Used with permission.

    
   

   Figure 6.2:  Growth in world population.  From Kenneth Sayre, Unearthed: The Economic Roots of our Environmental Crisis. Used with permission.

   
   By 5000 BC, world population stood roughly 5 million people, consuming about 6 billion joules per person per year. 
4. The next era in this very brief history began with the augmentation of human labor by oxen and horses.  Harnessing domestic animals brought additional muscle power to bear in food production and provided fertilizer needed to keep soil fertile.  By the time of the Roman Republic (roughly 1000BC), human population had grown to about 50 million.  Per capita annual consumption had more than doubled to 13 billion joules.
5. Further advances in food production were tied in with developing technology, including water wheels and windmills along with improvement in farm equipment.  At the onset of the Industrial Revolution (IR), around mid 17th century, world population had doubled several times to about 600 million people.  Per capita energy consumption had almost tripled to some 38 billion joules per annum.
6. The next period on the charts covers the first 150 years of the Industrial Revolution.  This period was marked by massive increases in the use of fossil fuel.  First coal replaced wood as the main fuel for steam engines.  Then internal combustion engines were invented to run on refined petroleum.  By the end of the 19th century, fossil fuels were running dynamos to produce electricity.
7. New methods of production were developed to take advantage of these fossil fuel sources.  Factories with central power units made mass production possible.  And with mass production came greater energy consumption per capita.  Mass production also reduced the price of goods, which (along with improvements in medicine and other factors) made it easier to raise large families.  By 1900, world population stood at about 1.6 billion, and per capita energy consumption at almost 56 billion joules per annum.

Energy consumption in 20th century

1. Now we turn to the 20th century.  One thing to note immediately is that a graphical presentation of growth in energy consumption during this period would be largely uninformative for comparative purposes.  As far as the eye could tell, a line representing this growth on the scale of Fig. 6.1 would go straight up.  Let us look at a few statistics instead.
2. At the start of the century, consumption of fossil and of renewable energy were approximately equal.  While growth in renewable energy use was tapering off during this period, however, use of fossil fuel increased a full 20 times over.  As a result of this rather astonishing increase, total human energy consumption at the end of the century stood at approximately 470 billion billion (1018) joules.  Given a population at that point of roughly 6 billion, this comes to about 79 billion joules per person.
3. In 1900, 1.6 billion people were consuming about 56 billion joules each, for a total of close to 90 billion billion.  By 2000, the total had increased from 90 to 470, giving an average of about 38 billion billion a decade.  During each decade of the 20th century, human energy consumption increased more than it had during the 2000 years or so leading up to the Industrial Revolution.  Even more startling is the consequence that human energy consumption increased more each single year of this century than during the entire 4 millennia leading up to the Roman Republic.
4. The biosphere is reeling under the impact of this astounding acceleration in energy consumption.  A basic lesson from the first lecture is that energy becomes degraded in use, and that degraded energy does not simply disappear.  For millions of years, the biosphere had been able to dissipate entropy generated by life processes back into space.  But this is no longer the case.  Substantial portions of entropy generated by human activity have been retained within the biosphere, with detrimental effects mentioned at the beginning of the present lecture.
5. Let us look once again at global warming.  A major cause of global warming is an excess of CO2 built up in the atmosphere.  A glance at another chart shown in the lecture video indicates that accumulations of CO2 in the air began to climb about 150 years ago and have grown more and more rapidly ever since.  The correlation between this growth curve and that of human energy consumption is eerie.  Putting these charts together helps us to see the connection between our energy consumption habits and the damage we are causing to the biosphere at large.
6. Viewing the graphs from another perspective, we see an acceleration of energy consumption that is veering out of control.  The rate of increase resembles that of a chemical explosion.  When gunpowder starts burning, the positive feedback by which increased temperature produces more rapid burning results in a process of combustion that appears instantaneous.  The same thing is happening with our industrial use of energy. 
7. In the manner of exploding gunpowder, the outcome toward which this process appears to be heading is the self-destruction of industrially based society.  Obvious questions arise in the wake of this ominous realization.  Why is humanity consuming ever increasing amounts of energy?  And what, if anything, can be done about it?  These questions set the topic of subsequent lectures.