## 15.2 The Limits of Nature

Let us reconsider first the assumption that nature is a potentially limitless pool of resources capable of supporting a limitless expansion of human society and consumption. Modern environmentalism, which first became a popular movement in the 1970’s arose as a challenge to this assumption on a number of fronts. One particularly powerful expression of this challenge was issued in 1972 by a group of scientists at the Massachusetts Institute of Technology who published a book called The Limits to Growth. In this book they argued that as a result of the growth of an industrial society based on the extensive use of fossil fuels like coal, oil and natural gas, humanity would soon be reaching some fundamental limits to its further expansion. The basis of their argument was a complex computer model simulating the interaction of numerous factors – human population growth, increases in consumption of natural resources and generation of wastes by increasingly affluent populations, increased food production as a result of the application of fossil fuel driven technology to agriculture, availability of basic resources like fresh water, food, oil, coal, metal ores, wood, etc. By running this model with different assumptions about the future, ranging from the optimistic “we will never run out of oil and can keep expanding our numbers indefinitely” to the pessimistic “we face immanent depletion of vital natural resources,” they found that in all cases sooner or later human populations would run up against some barrier or other that would prevent further expansion. Eventually we would hit some limits that prevented our further expansion. Depending on the particular starting assumptions these limits might appear as limits to the amount of pollution that could be absorbed by the environment, limits to the amount of energy resources available, limits to the amount of food we could produce, limits to the amount of fresh water available for human use, and so on. Interestingly enough, their simulations tended to show that whatever those barriers were, they would begin to appear at some point early in the 21st century. Now, these authors were not claiming to be able to predict the future, since their model was far too simple to take into account all of the numerous factors affecting the ability of humans to survive and thrive on the planet earth. But, as they point out in updated editions of their book, published in 1982 and in 2002, there is plenty of accumulating evidence that in fact we are currently running up against fundamental limits to the continued expansion of human society and resource usage. For my purposes here it will be enough to focus on three different areas in which the limits of nature are becoming more apparent to a wide range of scientists and non-scientists alike: climate change, oil depletion and loss of biodiversity. Each of these presents a challenge that we ignore at our peril. All three simultaneously will make life in the twenty first century very interesting indeed. And, from a purely philosophical perspective, all of these issues present fundamental challenges to the assumption that we need not worry about limits imposed on us from outside, by the natural world in which we live.

### Climate Change

The fact that the climate of the earth is fairly well-suited to human habitation is something most of us take for granted. Even though climactic conditions vary quite a bit from place to place – from the polar regions that are frozen much of the year, to temperate climates, to tropical deserts and rain forests – there are enough places on the planet in which the temperature is fairly well suited to comfortable human habitation, and in which there is ample rainfall or other sources of water for large scale agriculture. This has not however, always been the case on the planet earth. At times the overall climate on the planet has been cooler – much of the mid-latitude areas of Europe and North America were covered with vast ice sheets as recently as 15,000 years ago for instance. At other times global average temperatures have been warmer than at present. In addition, the current composition of the atmosphere – approximately 79% nitrogen and 20% oxygen with traces of other gases such as carbon dioxide making up the remainder – is not a permanent feature of the planet earth but is a product of long time-scale geological and biological processes. However, on a human time scale the climate and atmosphere have been relatively stable.

This relative stability of the earth’s climate within the time frame of human history is a result of complex geo-chemical processes in which the overall composition of the atmosphere has remained more or less constant, even though many elements and compounds are constantly moving between the large scale repositories of the earth’s crust, the biosphere, the oceans and the atmosphere. These so called bio-geochemical cycles are important for all living systems. Although there are many important cycles of different chemical elements and compounds, such as water, nitrogen, sulphur, phosphorus and carbon, the carbon cycle is particularly important for understanding the potential variability of the earth’s climate. The vast majority of the very abundant element carbon is in fact stored in carbonate minerals within the earth’s crust, but a relatively small amount of carbon cycles through the atmosphere. It is absorbed by plants from the atmosphere and incorporated by plants into sugars, starches and cellulose, and then taken up into animals who eat the plants for the energy stored up in the carbon based molecules that plants contain. In the process of extracting this energy, carbon is then combined with oxygen and released into the atmosphere as carbon dioxide gas. Some of this gas is reabsorbed by plants, and some dissolves in the oceans where it is captured and used by shelled aquatic organisms to construct their shells. Eventually these die and their carbonate shells settle to the sea floor where they are incorporated back into carbonate rocks, which in turn are mixed into the earth’s slowly moving crust, occasionally finding their way to the surface where they are exposed to weathering and may thus return to the atmosphere.

This is somewhat of an oversimplification of a very complex process, but it is a good enough picture for grasping the basic mechanism of climate change. To understand this mechanism, one more piece needs to be added to the puzzle. In addition to its role in the biological world, carbon dioxide is one of many so-called “greenhouse gases.” Greenhouse gases are so named because they act just like the glass in a greenhouse does – they allow visible light to enter the atmosphere (or greenhouse) which warms objects on the surface of the earth (or within the greenhouse); these in turn radiate some of their heat back outwards as infrared radiation, which is, however, reflected back by greenhouse gases (or glass) thus raising the temperature inside the atmosphere (or greenhouse). Greenhouse gases (and glass) do this since their molecular structures allow only certain wavelengths through, blocking and reflecting others. Because of this property of gases like carbon dioxide, the climate of the earth is highly sensitive to variations in the amount of carbon dioxide in the atmosphere. This is not a new discovery – in fact the “greenhouse effect” was discovered way back in 1824 by the French mathematician and scientist Joseph Fourier. But in the 1970’s climatologists began to get increasingly worried about the scale of climactic changes possibly resulting from drastic increases in the amount of carbon dioxide humans were releasing into the atmosphere through our burning of enormous amounts of fossil fuels. Worldwide at present our burning of fossil fuels pumps approximately 3 billion tons of carbon into the atmosphere every year in the form of carbon dioxide gas. In addition deforestation has caused an additional increase of approximately 1 billion tons per year of carbon dioxide that is no longer absorbed by those forests which have been cut down for crop and pasture land or for the spread of urban and suburban development. Altogether in the last century and a half the concentration of carbon dioxide in the earth’s atmosphere has increased by more than 30%, and the rate of emissions of carbon dioxide and other greenhouse gases has been accelerating as more and more of the world embraces industrial development and a consumer oriented lifestyle heavily reliant on the worldwide transportation of goods, personal mobility and increased energy usage.

The effects of this increase of greenhouse gases are becoming increasingly clear to the world’s climate scientists and policy makers, in spite of the resistance of some vocal skeptics to this picture. Although the exact nature of changes to a system as complex as the global climate are hard to predict with any accuracy, we can still get a general sense of what we can expect the future to be like. We can expect such things as rising sea levels as more of the water currently locked up in ice caps and glaciers melts; increasingly violent storms as more solar energy is captured by the hurricane and typhoon generating central ocean belts; shifting patterns of rainfall that will move around the world’s deserts and agriculturally productive regions; increased levels of species extinctions as species not capable of moving to new locations rapidly find themselves living in a changing environment. That all of this, or even just some of this, will have an enormous impact on human societies almost goes without saying. Consider only rising sea levels and the effects that this will have on the world’s current population centers, many of which are at or near sea level – in the U.S. alone New York, Boston, Baltimore, Miami, Houston, San Diego, Los Angeles, San Francisco, Portland and Seattle as well as many smaller cities are at or near sea level and so will have to deal with more flooding and a loss of available land area on which to build and house people. Worldwide an estimated 650 million people (10% of the population of the planet) live at or near sea level. Clearly we are at or crossing some important limits with our continued burning of fossil fuels. Somewhat paradoxically, this burning of fossil fuels is also entering into an age of limits, which brings us to the next of the three major challenges mentioned above.

### Oil Depletion

All of us who are currently alive have lived our entire lives in a time of cheap and abundant energy, a situation which is unique in human history. This is something we have come to take for granted – the fact that modern industrial and consumer society is built on the exploitation of fossil fuels – oil, coal and natural gas. It is easy to forget that as recently as 150 years ago, there were no and had never been any cars, airplanes, trucks, buses, trains, oil tankers, plastics, synthetic fabrics, artificial fertilizers, or pesticides, let alone all of the modern electricity generating, manufacturing, transportation and communications infrastructure that enables us to live in the most complex society that has ever existed. Without oil (and to a lesser extent coal and natural gas) none of this would be possible. Consider, for example, what is in the background of a simple everyday activity – grilling a hamburger on a backyard grill. In order for this to take place first corn and soybeans were grown in a large field fertilized with artificial fertilizer (made from natural gas), sprayed with pesticides and herbicides (derived from oil), both applied with tractors running on diesel fuel, which also fuels the numerous plowing, planting harvesting and processing machines used by the grain farmer. These grains were then transported to a feed mill (by truck or diesel powered train) processed into feed which is transported (by truck or train) to a feed lot where it was fed to cows (brought there by truck) until the cows were again transported by truck, slaughtered and butchered, wrapped in plastic packaging (made from oil) and shipped by truck to a refrigerated case (manufactured of metal and plastic, kept cool with a refrigerant derived from oil) in the supermarket. To get to the supermarket the consumer probably drove in a car that runs on gasoline, and then bought the hamburger meat and rolls (also produced with many fossil fuel inputs) with the currency (the US Dollar) that keeps its value in part owing to the fact that it is the standard currency for buying and selling oil around the world. After he or she drove home and unwrapped the hamburger, he or she slapped it on the grill (fueled by propane, an oil derivative), cooked it to perfection, ate it and then threw the waste out in the trash where it now awaits pickup by the garbage truck. All told for every one calorie of food energy you eat, approximately 10 calories of fossil fuel energy had to be consumed in its production and transportation, not including the energy used in cooking. We could say without really exaggerating things that the modern industrial food system is a method for using crop land to convert fossil fuels into food. The same applies to most things we take for granted as part of life in a modern industrial consumer economy – oil and other fossil fuels are used to power the entire world economy as well as supply it with numerous raw materials used to feed, clothe, transport, house and employ and entertain much of the world’s population. We truly live in the age of fossil fuels.

Unfortunately fossil fuels will not be available forever – they are a non-renewable resource, the result of a unique combination of geological events some hundreds of millions of years ago which folded an enormous mass of decaying plant matter into geological formations where it was subject to heat and pressure resulting in oil, coal and natural gas deposits fairly close to the surface of the earth. Fossil fuels are in effect millions of years worth of solar energy that was captured by plants and has been stored underground for a very long time. Because of this we will eventually run out of oil, coal and natural gas. Well that much is probably obvious. On the other hand, it might seem that this is not a problem that we currently have to face since, according to the most widely accepted estimates, we have in the last 150 years used up at most half of the oil, and slightly less than half of the coal and natural gas that can be extracted (not all fossil fuels in the ground can be extracted since some is so far down and of such poor quality that it is simply not economically worth it to try to get it out – it would cost more money to get it out of the ground than it could be sold for). However, it is important to recognize that oil in the ground is not really like gasoline in the tank of your car. When you run out of gas it is a sudden event – one second you are driving happily along and the next moment your car sputters to a stop as you realize that you forgot to get the gas gauge fixed. Oil and other resources that are available in limited supplies are extracted according to a pattern that has come to be known as the Hubbert Curve after the petroleum geologist who first described and studied the rates of production and depletion of oil wells, oil fields and oil producing regions – M. King Hubbert. The basic pattern of oil extraction goes like so:

• When an oil discovery is made it takes a little while for production to begin and then it starts flowing slowly at first simply because it takes time to drill wells and get the oil to market.
• As more wells are drilled and as long as the demand for oil continues to grow, more oil is extracted from individual wells and the oil field as a whole.
• Eventually production peaks as the maximum flow rate of oil is attained, a rate determined by the complex geology of oil deposits as well as physical characteristics of crude oil.
• After the peak in production (when roughly half of the extractable oil has been pumped out of the well and/or oil field), production declines since the remaining oil is typically harder to get out than the easily flowing oil extracted initially.
• Finally, the rate of extraction tapers off to nothing and the oil wells are shut down.

Hubbert realized that not only individual wells and oil fields follow this bell-shaped curve in their rates of production, but so did oil producing regions and countries as well as the world as a whole. As a result of his examination of the available data on worldwide oil regions in 1958 he estimated that the United States, which was then the country that produced more oil than any other country in the world, would reach its peak of production (“peak oil”) in approximately 1970 and that world oil production would peak in the first decade of the twenty first century. In fact the production of oil in the U.S. peaked in 1970 and except for a temporary upsurge in production in the 1980’s when oil from Alaska’s remote North Slope oil fields came on line, has been in decline ever since in spite of ever more intensive exploration and major improvements in exploration, drilling and extraction technology. Ever since then the U.S. has become increasingly dependant on importing oil from other countries. As for the peak in world oil production, it is unclear when it will happen, if it hasn’t already happened. Many oil industry analysts say that it will happen sometime within the next decade although a growing chorus agrees that the world peak in oil production was reached in July of 2008.

So far all of this may seem like an issue that is of interest only to oil industry executives and petroleum geologists. That this is not the case and that the peaking of oil production worldwide is an event with historic implications is a point that I cannot fully defend here for lack of space. It will have to suffice here to simply point out that until this point the amount of oil produced and consumed by a growing worldwide industrial consumer economy has been steadily rising. Economic growth has always required growth in the amount of energy used and this has been possible owing to growth in the amount of oil produced each year. But now we are entering into an age in which the expansion of energy supply is not something that can be taken for granted. In fact, if the so-called “peak oil” theorists are correct, we are now facing a decline the amount of available energy for the first time since the beginning of the industrial revolution 150 years ago. The practical implications of this are huge, if still difficult to pin down with any degree of confidence. To get a sense of this, simply imagine the implications if the price of oil were to increase to say 10 times its current price and this price affected the prices of all of the things in our lives that depend on oil such as transportation, food production, manufacturing, etc. Would we be able to afford to live as we currently live if things in general were to suddenly jump in price owing to decreasing supply of the one resource which, above all others, we have come to rely upon?

### Loss of Biodiversity

The third of the limits to the expansion of human activities, population, levels of consumption and so on is the simplest to grasp but probably the one that has attracted the least amount of public concern. This is namely the loss of biodiversity, or put more simply the currently unfolding mass extinction of species. Scientists estimate that there are currently from 10,000,000 to 30,000,000 different species of living organisms on the planet earth. None of these species will be around forever, all will eventually go extinct. To get a sense of the problem we now face, however, we can compare the “normal” or background rate of extinction to the rates we are currently experiencing. In the normal course of events, due to factors like changes in the particular environment in which a species lives, unpredictable events that cause major disruptions such as earthquakes, tidal waves, fires and landslides, approximately one species goes extinct every year. It fails to adapt to changes or to competition from other species for the the resources on which its survival depends and thus vanishes from the face of the earth. At present however, and for a number of different reasons I will spell out in a minute, this normal background rate has accelerated to the point that one species is now going extinct about every 30 minutes. This rate of extinction is about 10,000 times the normal background rate. If it continues, and there is every reason to think that it will continue, within the next 100 years approximately one half of all species of living organisms will have vanished from the face of the earth. Behind this enormous increase in species extinction are a number of interrelated factors, all of which, in a sense reduce to one simple fact – that there is not enough room on a finite planet for ever increasing numbers of any species, especially one as resource hungry as we are. And yet us humans have managed to increase our numbers and our impacts to the extent that we are now crowding others out of existence. The particular factors that are leading to what can only be called a mass extinction (of which there have been 5 in the history of the planet earth, the most famous of which was the event that caused a massive climate shift thus wiping out the dinosaurs some tens of millions of year ago) are:

1. loss of habitat to human agriculture, logging, and urban and suburban development;
2. habitat fragmentation into smaller and smaller regions (this is particularly hard on species that depend on continuous ranges of similar habitat, such as grizzly bears or wolves in North America);
3. overexploitation through over-hunting or over-fishing;
4. climate change – as the global climate changes many less mobile species simply cannot respond quickly enough to changing local conditions;
5. pollution.

The first of these causes of species extinction is by far the most damaging. As human populations both grow and attain higher levels of affluence our environmental impacts get larger and larger. That is, adverse environmental impacts are not simply a matter of the number of people there are (the problem of so-called “overpopulation”), since the share of the earth’s resources used by a single person living in the suburbs of Los Angeles uses can be as much as 20 times the amount used by the average person living in a developing country like India. Environmentalists remind us that our impact depends not only on population, but also on our lifestyles and the level of technology we use. In the famous formula:

$$I = P \times L \times T$$

In other words, it matters (our environmental impact $$I$$ is based upon) not just how many of us there are (our population $$P$$), but whether or not we live in a 6,000 square foot house, eat steak three nights a week and drive everywhere (our lifestyle $$L$$) in a gas guzzling car or a hybrid (the technology we use $$T$$).