MAKING PEACE WITH THE PLANET:
POPULATION AND POVERTY
by Barry Commoner
One of the virtues of the environmental point of view is that we see the planets a harmonious whole, a global system of water, soil and living things bounded by the thin skin of air. However when we look at the planet with an eye on human manifestations ---the technosphere and the social systems that create it---it is split in two. The northern hemisphere contains most of the modern technosphere---its factories, power plants, automotive vehicles, and petrochemical plants---and the wealth that it generates. The southern hemisphere contains most of the people, nearly all of them desperately poor.
The result of this division is a painful global irony: the poor countries of the south, while deprived of an equitable share of the world's wealth, suffer the environmental hazards generated by the creation of that wealth in the north. The developing countries of the south will not only experience the impact of global warming and ozone depletion, which are now chiefly due to the industrialized countries, but are also victimized by the north's toxic exports. For example, as bans have been imposed on particularly dangerous pesticides in industrialized countries, manufacturers have marketed them in developing countries instead. There, poorly regulated, they have created in the bodies of local populations the world's highest concentrations of pesticides. Similarly, as environmental concerns have limited disposal sites trash and the toxic trash-burning incinerators in the United States, efforts have been made to get rid of these pollutants---not always successfully---in developing countries.
Yet the gravest threat of the environmental crisis to developing countries comes, nor from pollutants so generously imposed on them by their wealthy planetary neighbors, but from a more subtle source, This threat arises from a serious, frequently voiced misconception about the origin of the environmental crisis. In this and earlier analyses, I have argued that the environmental crisis originates, not in the natural ecosphere, but in the man-made technosphere. The data about both the development of the post-1950 assault on the environment and the effort since 1970 to reduce it support this conclusion. There is, however, another view of the environmental crisis that turns these relationships upside down. This view holds that the problem is ecological; that environmental degradation originates in an imbalance between the earth's limited resources and the rapidly growing human population, which stresses the environment and also causes social problems such as poverty and hunger.
This position had a popular following in the early days of the environmental movement, based on the unequivocal assertions by some well-known environmentalists. In a widely quoted article, "The Tragedy of the Commons". Garret Hardin put it this way:
The pollution problem is a consequence of population. It did not matter much how a lonely American frontiersman disposed of his waste....But as population became denser, the natural chemical and biological recycling processes became overloaded....Freedom to breed will bring ruin to all.
Paul Ehrlich's best-seller, The Population Bomb, was even more explicit about the origin of the environmental crisis:
The causal chain of the deterioration [of the environment] is easily followed to its source. Too many cars, too many factories, too much detergent, too much pesticide, multiplying contrails, inadequate sewage treatment plants, too little water, too much carbon dioxide---all can be traced easily to too many people.
In the early 1970's, such statements encouraged the view that population control is the only practical way to reduce pollution, a notion that some environmentalists took personally. Visiting a midwestern university in the early 1970s, I recall a conversation with a pregnant faculty member who had received anonymous letters condemning her for contributing to the environmental crisis. Enthusiasm for contraception as an environmental strategy has faded considerably, although recently the head of the National Organization for Women (NOW), desperate for allies in the fight against the Supreme Court's invitation to state control of abortions, sought to enlist environmentalists on these same grounds. This basic position is still held by a number of leaders of the environmental organizations that have grown to prominence since the early 1970s. Russell W Peterson, the former president of the National Audubon Society, a major environmental organization, expressed it this way a few years ago:
"Almost every environmental problem, almost every social and political problem as well, either stems from or is exacerbated by the growth of human population....As any wildlife biologist knows, once a species reproduces itself beyond the carrying capacity of its habitat, natural checks and balances come into play....The human species is governed by this same natural law. And there are signs in many parts of the world today---Ethiopia is only one of many places, a tip of the iceberg---that we Homo Sapiens are beginning to exceed the carrying capacity of the planet".
Such statements send a chilling message to developing countries. They are in a desperate struggle to improve living standards, and---in violation of Mr. Peterson's dictum---are eager to use more resources to support their rapidly growing populations. Surely sweeping prescriptions such as those just cited, which affect the destiny of most of the world's people, ought to be solidly founded in fact. Are they?
The chief source of these views is a fundamental ecological concept regarding the relationship between the eater and the eaten. In a normal ecological system, there is a balance between a species' population and its food supply. If rabbits reproduce at the rate at which they are eaten by wolves and the wolves reproduce at the rate at which they die or are killed by hunters, both populations will be stable in size. Suppose, however, that some outside influence on the wolves' death rate is eased---fewer hunters, perhaps---so that their population rises above the equilibrium size. Now the rabbits are likely to be eaten faster than they can reproduce, and their population will decline, reducing the "carrying capacity" of the ecosystem for wolves. The wolf population will then short of food, die off faster, and become smaller until it is once more in balance with the rabbits.
Applied to human beings, this concept suggests that in a country like Ethiopia, devastated by repeated famines, starvation is a symptom of overpopulation, and--in the absence of outside intervention---a precursor to a catastrophic population decline that will restore the balance between its size and the county's limited food supply. Relying on this concept, some environmentalists urge population reduction and oppose famine relief as a misguided, futile gesture. Thus, Garret Hardin provides this explanation of why he is opposed to feeding hungry countries:
"When we send food to a starving population that has already grown beyond the environment's carrying capacity we become a partner in the devastation of their land. Food from the outside keeps more natives alive; these demand more food and fuel; greater demand causes the community to transgress the carrying capacity more. and transgression results in lowering the carrying capacity in the future. The deficit grows exponentially. Gifts of food to an overpopulated country boomerang, increasing starvation over the long run. Our choice is really between letting some die this year and letting more die in the following years....Only one thing can really help a poor country: population control."
Apart from humane considerations, there is a ready response to this position: if the necessary funds were available, by applying modern production processes, Ethiopia could increase food production and if needed be use its increased wealth to import it. But such reliance on economic growth and development is also regarded as ecologically unsound by population-minded environmentalists, for in Paul Ehrlich's terms, it would only lead to "too many cars, too many factories, too much detergent, too much pesticide" and the inevitable deterioration of the environment.
This approach has been elaborated on a global scale by means of computer models that purport to show, mathematically, that the interaction between a growing world population, the economic growth impelled by it, and the resultant environmental degradation and food shortages leads inevitably to the kind of population crash experienced by wolves in an ecosystem of too few rabbits. This conclusion was reached by the Club of Rome (a self-appointed organization of industrialists and environmentalists) in a report that was widely publicized, but less widely acclaimed for its scientific soundness, The Limits to Growth.
The "limits to growth" approach is based in a serious misconception about the global ecosystem. It depends upon the idea that the Earth is like a spaceship, a closed system isolated from all outside sources of support and necessarily sustained only by its own limited resources. But the ecosphere is not in fact a closed, isolated system, for it is totally dependent on the huge influx of energy from an outside source---the sun. Living things must be provided with energy to sustain their vital processes, in particular growth, development, and reproduction. That energy is derived from the sun. Sunlight, absorbed by plants, drives the energy-requiring chemical reactions that synthesize the complex organic compounds characteristic of life, such as protein, carbohydrates, fat, and nucleic acids. This process, photosynthesis, is the gateway that brings solar energy into the ecosphere: the rabbit, nibbling vegetation, derives its energy from the plant's organic compounds; the wolf obtains its energy by devouring the rabbit. Such food chains transmit the solar energy initially captured by plants throughout the ecosphere.
Thus, solar energy, captured by photosynthesis, sustains every form of life and drives the ecological cycles in which they participate. If an ecological cycle is viewed only as a static array of animals, plants, and microorganisms linked through the physical environment into a circular system, it appears to be closed, like a ring. But this image is misleading, for without the energy that it receives, externally, from the sun, the plants and animals would die and the circular system would disintegrate.
Solar energy also creates the weather: the seasonal temperature changes; the wind and the storms that carry rain and snow to the soil and replenish the lakes and rivers that feed the oceans. In turn, the weather molds the physical features of the Earth's surface, creating the ecological niches that living things occupy. In sum, the global ecosystem is not, in the basic thermodynamic sense, an isolated, self-sufficient system. In fact, neither is a spaceship, which after all depends for the energy that operates it on electricity generated by photovoltaic cells---from the sun.
In an abstract sense, there is a global "limit to growth", but this is determined not by the present availability of resources but by a distant limit to the availability of solar energy. It is true, of course, that the ecosystem that occupies the Earth's thin skin, and the underlying mineral deposits, are essential both to population growth and economic production. It is also true that there is a potential limit to economic growth due to the finite amounts of these essential resources. However, since matters, after all, indestructible, the chemical elements that comprise the planet's resources can be recycled and reused indefinitely, as long as the energy necessary to collect and refine them is available. This is precisely what is done when the resource is sufficiently valuable; despite its extensive dispersion, well over half of all the gold ever mined is still in hand today, regathered when necessary by expending energy. Hence, the ultimate limit on economic growth is imposed by the rate at which renewable, solar energy can be captured and used. If we ignore the exceedingly slow extinction of the sun, this limit is governed only by the finite surface of the Earth, which determines how much of the energy radiated by the sun is actually intercepted and is therefore capable of being used.
Thus, the theoretical limit to the growth of the global economy is determined by the rate at which the Earth receives solar energy. How close is this limit at present? It has been estimated that the solar energy that falls annually only on the Earth's land surface is more than a thousand times the amount of energy (almost entirely from fuels, hydroelectric and nuclear power) now being used each year to support the global economy. Of course, because some parts of the land are difficult to reach or otherwise unsuitable, not all of the solar energy that falls on it could be used. If, let us say, only 10 percent of the total solar energy falling on land could be captured, it would still be possible to expand our present rate of using energy a hundredfold before encountering the theoretical limit to growth. Even if this figure should turn out to be somewhat optimistic, it seems clear that we are at present nowhere near the limit that the availability of solar energy will eventually impose on production and economic growth. That distant limit is irrelevant to current policy.
The issue we face, then, is not how to facilitate environmental quality by limiting economic development and population growth, but how to create a system of production that can grow and develop in harmony with the environment. The question is whether we can produce bountiful harvests, productive machinery, rapid transportation, and decent human dwellings sufficient to support the world population without despoiling the environment.
It is useful at this point, to turn to the data that relate environmental deterioration to the factors that influence it. As we have seen, production technologies differ considerably in their tendency to pollute the environment. Consider, for example, the different environmental impacts of two alternative technologies of beer distribution: the throwaway bottles, and the returnable bottles that are likely to be used forty times before being broken or discarded. Each bottle contains an economic good---twelve ounces of beer--- and the production of that good is associated with a pollutant: the bottle discarded as trash. We can compare the pollution-generating potential of the two technologies by computing the number of beer bottles used to deliver each twelve ounces of beer. In the case of the throwaway bottles, the figure is one bottle per twelve ounces of beer; for returnable bottles, the figure is 1/40 bottle per twelve ounces of beer. Thus, the pollution-generating tendency of a technology can be expressed numerically as the amount of pollution generated in producing a unit amount of economic good.
The total amount of pollution generated can then be expressed by multiplying this "technology factor" (pollution per unit good) by the total amount of good produced. Finally, the later figure can be broken down into the product of two factors: good produced per capita (the "affluence factor") multiplied by the size of the population. In this way, the total amount of pollution can be expressed numerically in the form of an equation:
total pollution = pollution per unit good x good per capita x population
This relationship shows that the total amount of pollution generated will increase if any of the three factors increases. Thus, it is possible to say with equal validity that environmental deterioration---say, the number of beer bottles---is exacerbated by "too many people" as Paul Ehrlich claims, or, in keeping with my own analysis, by a change in the technology of production that increases the number of bottles used to deliver twelve ounces of beer. And it is equally possible that the number of discarded beer bottles will increase because of greater beer consumption per capita. What is at issue is the relative impact of each of these factors on environmental pollution. Such an evaluation will indicate which factor, if reduced, provides the most effective means of improving environmental quality.
In the United States, data are readily available to evaluate the relative effect of the three factors on a number of pollutants.In the case of beer bottles, they show, for example, that between 1950 and 1967, as the number produced annually increased by 593 percent, the population increased by 30 percent, per capita beer consumption (the affluence factor) rose by 5 percent, and the number of bottles used per unit of beer shipped (the technology factor) increased by 408 percent. Clearly, the largest impact on the amount of beer bottle trash was due to the technology factor: the introduction of nonreturnable bottles, which sharply increased the number of bottles needed to ship a unit amount of beer.
The relative impact of the three factors in reducing the environmental impact of the beer bottle trash between 1950 and 1967 is indicated by the following: if there had been no change in the technology of beer distribution, the number of beer bottles would have increased by 37 percent; if only population had remained constant, the number of beer bottles would have increased by 433 percent; if only the affluence factor had remained constant, the number of beer bottles would have increased by 560 percent. Clearly, an effort to change the technology of beer distribution will result in the greatest reduction in environmental impact.
The pattern revealed by the beer bottle data is typical of the new post-1950 production technologies. For example, between 1950 and 1967, when pesticide use for crop production increased by 266 percent, the population increased by 30 percent, crop production per capita (the affluence factor) by 5 percent, and the amount of pesticide used per unit of crop production (the technology factor) by 168 percent. In the case of phosphate, an important water pollutant, emissions into surface waters increased by 1,845 percent between 1946 and 1968, while population rose by 42 percent, the amount of cleanser per capita remained constant, and the amount of phosphate per unit amount of cleansers increased by 1,270 percent due to the technology factor: the introduction of phosphate-containing detergents in place of soap. Similarly, between 1946 and 1967, when nitrogen oxides emitted by cars increased by 628 percent, population rose by 41 percent, vehicle miles per capita doubled, and and nitrogen oxides emitted per mile increased by 158 percent.
It is apparent, then, that in the United States the factor most responsible for the sharp increases in pollutants since World War II---and the factor most capable of reducing pollution---is production technology: the new methods used to produce vehicular travel, cleansers, crops, beer, and many other goods. It can be argued, of course, that in developing countries the situation is different and that their impact on the environment is in fact largely due to what many people regard as their most prominent feature---rapid population growth. Unfortunately, the available data on pollutant levels in developing countries are scanty and incomplete, so that a numerical analysis such as that described for the United States is impossible. However, the problem can be approached indirectly, based on what is already known about the relation between certain pollutants and the production processes that generate them.
For example, it has been established that the rising levels of nitrate---a pollutant that contributes to eutrophication and to heath problems in drinking water supplies---in U.S. and European surface waters is largely due to the application of nitrogen fertilizer to crops. Where such data have been obtained, about 20 to 25 percent of the applied nitrogen reaches surface waters. Hence, subject to this range of uncertainty, the amount of of nitrogen fertilizer applied to crops can be used, as a proxy, to represent the resultant level of nitrate in surface waters. Thus, the relative effects of the population, affluence, and technology factors on the pollutant, nitrate, can be estimated if, for a given country or area, changes over time in the following factors can be compiled: population; crop production per capita; and nitrogen fertilizer used per unit crop.
Data on these factors for the period 1970-1980 are available for most developing countries, they are conveniently expressed as the annual rate of change. In ninety developing countries, nitrogen fertilizer use (a proxy for nitrate pollution) increased by an average of 8.6 percent per year, while the rise in population averaged 2.5 percent per year, crop production per capita (affluence) decreased by 0.06 percent annually, and fertilizer use per unit crop production (the technology factor) increased by 6.6 percent. the impact of the technology factor on the amount of nitrogen fertilizer used, and hence on the level of of nitrate pollution, considerably outweighs the effect of both the rapidly rising population and and "affluence". Similar analysis show that the introduction of automotive vehicles and power plants in developing countries has had a significantly greater impact on the resultant pollution levels than either population or "affluence".
In sum, the data both from an industrial country like the United States and from developing countries show that the largest influence on pollution levels is the pollution-generating tendency of the system of industrial and and agricultural production, and the transportation and power systems. In all countries, the environmental impact of the technology factor is significantly greater than the influence of population size or of affluence.
What does this mean for developing countries, where increased production is the engine of economic progress? At present, developing countries usually introduce those technologies that have proven to be both highly productive and ecologically unsound in industrial countries---nitrogen fertilizer, for example. As pointed out in the recent Bruntland report, the upshot is that "the industries most heavily reliant on environmental resources and most heavily polluting are growing most rapidly in the developing world, where there is more urgency for growth and less capacity to minimize damaging side effects."
Thus, especially in developing countries, the question of environmental quality is an inseparable component of the issue of economic development. To claim that the two are in conflict and that environmental quality can only be achieved at the expense of development ignores the dominant role of production technologies in determining environmental impact. Economic development can proceed without a concomitant decrease in environmental quality if it is based on an appropriate, ecologically benign production technology. For example, crop production can be increased without incurring the environmental hazards of conventional chemical agriculture by practicing organic farming instead. The apparent conflict between environmental quality and economic development that motivates proposals to limit the growth of population and/or production can be largely eliminated by the proper choice of production technologies.
What, next, is the evidence that overpopulation is responsible for famine? Hunger is widespread in the world and those who believe that the world's resources are already insufficient to support the world population cite this fact as evidence that the world is overpopulated. Once more, it is revealing to examine the actual data regarding the incidence of malnutrition. It is useful to remember that people in other countries did not go hungry because they sent food to Ethiopia to relieve the famine there---that what was sent to Ethiopia was surplus food. In fact, the world produces more than enough food to feed the total world population. Total world production of food, equally distributed to the global population, would today provide everyone with more than enough for the physiologically required diet. According to a recent estimate by the United Nations Food and Agriculture Organization, the world produces enough grain to provide every person on earth with 3,600 calories a day---more than one and a half times the calories required in the normal diet. Enough grain is produced to give everyone on earth two daily loaves of bread.
Famine is caused , not by a global food shortage, but by the grossly uneven distribution of the global food supply. This is not an ecological phenomenon but a political and economic one. Neither England nor Haiti produces enough food for its own population, but hunger is much more prevalent in Haiti than in England, because Haiti cannot afford to import enough food to make up the deficit, while England can.
Hunger and malnutrition are also a consequence of maldistribution of food within a country. From a detailed study of nutritional levels among various populations in India in 1967, we learn, for example, that in Madras State more than one-half the population consumed significantly less than the physiologically required calories and protein in their diet. However, the average values for all residents in the state represented 99 percent of of the caloric requirement and 98 percent of the protein requirement. What this means, of course, is that a significant part of the population received more than the required dietary intake. About one-third of the population received 106 percent of the required calories and 104 percent of the required protein; about 8 percent of the population received 122 percent of the caloric requirement and 117 percent or more of the protein requirement. These dietary differences were determined by income. The more than one-half of the population that received significantly less than the physiologically required diet earned less than $21 per capita per year, as compared with the state-wide average of $33. What these data indicate is that hunger in Madras State, defined simply in terms of a significantly inadequate intake of calories and protein, was not the result of too many people and not enough food. Rather, it resulted from the social factors that govern the distribution of available food---and income---among the population.
Thus, the available data about both hunger and environmental quality in developing countries show that they have been governed less by population size than by the countries' economic status and the kinds of production technology employed. It remains true, nevertheless, as shown by the multiplicative relation among the three factors that govern pollution, that, other things being equal, a rising population will contribute to the demand for food and to environmental stress.. Even though the impact of population on environmental quality is less than the effect of technology of production, in developing countries is not negligible, and must be taken into account. It is of interest, therefore, to consider what is known about the stabilization of human population and how that demographic process is related to biological factors such as birth and death rates, and social factors such as economic development.
Like all living things, people have an inherent tendency to multiply geometrically---that is, the people there are the more people they tend to produce. In contrast, the supply of food rises more slowly, for unlike people it does not increase in proportion to the existing rate of food production. This is, of course, the familiar relationship described by Malthus that led him to conclude that the population will eventually outgrow the food supply (and other needed resources), leading to famine and mass death. The problem is whether other countervailing forces will intervene to limit population growth and to increase food production.
When we turn from merely stating the problem to analyzing and attempting to solve it, the issue becomes much more complex. The simple statement that there is a limit to the growth of the human population, imposed on it by the limited availability of the necessary resources, is a useful but abstract idea. In order to reduce it to the level of reality in which the problem must be solved, we need to analyze the actual relationship between population growth and resources. Current views on this question are neither simple nor unanimous.
One view is that the cause of the population problems is uncontrolled fertility, the countervailing force---the death rate---having been weakened by medical advances. According to this view, given the freedom to do so, people will inevitably produce children faster than the goods needed to support them. It follows then, that the birth rate must be deliberately reduced to the point of "zero population growth".
The methods that have been proposed to achieve this kind of direct reduction in birth rate vary considerably. One method is family planning: providing people with effective contraception and access to abortion facilities and educating them about the value of having fewer children. Another suggestion, sometimes called the "lifeboat ethic", is to with-hold from the people of starving developing countries which, having failed to limit their birth rate sufficiently, are deemed to be too far gone or too unworthy to be saved. The author of this so called ethic, Garret Hardin, stated it this way:
"So long as we nations multiply at different rates, survival requires that we adopt the ethic of the lifeboat. A lifeboat can hold only so many people. There are more than two billion wretched people in the world---ten times as many as in the United States. It is literally beyond our ability to save them all. ... Both international granaries and lax immigration policies must be rejected if we are to save something for our grandchildren."
But there is another view of population that is much more complex. It is based on the evidence, amassed by demographers, that the birth rate is not only affected by biological factors, such as fertility and contraception, but also by equally powerful social and economic influences. Demographers have delineated a complex network of interactions among the various biological and social factors. It shows that population growth is not the consequence of a simple arithmetic relationship between birth rate and death rate. Instead, there are circular relationships in which, as in an ecological cycle, every step is connected to several others.
Thus, while a reduced death rate does, of course, increase the rate of population growth, it can have also the opposite effect, since families usually respond to a reduced rate of infant mortality by opting for fewer children. This negative feedback modulates the effect of a decreased death rate on population size. Similarly, although a rising population increases the demand on resources, it also stimulates economic activity, which in turn improves educational levels. This tends to rise the average age at marriage and to facilitate contraceptive practices, leading to a reduced birth rate, which mitigates the pressure on resources.
In these processes, there is a powerful social force that reduces the death rate (thereby stimulating population growth) and leads people voluntarily to restrict the production of children (thereby reducing population growth). That force, simply stated, is the quality of life: a high standard of living; a sense of well-being; security in the future. when and how the two opposite effects of this force are felt differs with the stages in a country's economic development. In a premodern society, such as England before the industrial revolution or India before the advent of of the English, both death rates and birth rates were high. But they were in balance and population size was stable. Then, as agricultural and industrial production began to increase and living conditions improved, the death rate began to fall. With the birth rate remaining high, the population grew rapidly. However, some thirty to forty years later, as living standards continued to improve, the decline in the death rate persisted, but the birth rate began to decline as well, reducing the rate of population growth.
Swedish demographic data, which are particularly detailed, provide a good example of this process. In around 1800, Sweden had a high birth rate, about 33 per 1,000 population, but since the death rate was equally high, the population was in balance. Then as agriculture and, later, industrial production advanced, the death rate dropped until, by the mid-nineteenth century, it stood at about 20 per 1,000. Since the birth rate remained virtually constant during that period, there was a large excess of births over deaths and the population increased rapidly---an early version of the "population explosion". Then the birth rate began to drop, until in the mid-twentieth century it reached about 14 per 1,000, when the death rate was about 10 per 1,000. Thus, under the influence of a constantly rising standard of living, the population moved, with time, from a position of balance at high birth and death rates to a new position of near balance at low birth and deaths rates. But in between, the population increased considerably.
This process, the demographic transition, has been characteristic of all industrialized countries. In these countries, the death rate began to decline in the mid-eighteenth century, reaching an average of 30 per 1,000 in 1850, 24 per 1,000 in 1900, 16 per 1,000 in 1950, and 9 per 1,000 in 1985. In contrast, the birth rate remained constant at about 40 per 1,000 until 1850, then dropping rapidly, reaching 32 per 1,000 in 1900, 23 per 1,000 in 1950 and 14 per 1,000 in 1985. As a result, populations grew considerably, especially in the nineteenth century, then slowed to the present net rate of growth of 0.4 percent per year.
The same process has been under way in developing countries, but with a longer time lag between the declines in death rate and birth rate. In developing countries, the average death rate was more or less constant, at about 38 per 1,000 until 1850, then declined to 33 per 1,000 in 1900, 23 per 1,000 in 1950, and 10 per 1,000 in 1985. The average birth rate, on the other hand, remained at a constant high level, 43 per 1,000, until about 1925; it has since declined at an increasing rate, reaching 37 per 1,000 in 1950, and 30 per 1,000 in 1985. As a result, the increase in population of the developing countries that began around 1850 has started to slow down and those county's populations are now growing at an average rate of 1.74 percent annually. It is important to note that the death rates of developed and developing countries are now nearly the same and, given the inherent biological limits, are not likely to decline much further. Thus, in developing countries the progressively rapid drop in birth rate will accelerate progress toward populations that, like those of developed countries, are approximately in balance.
To be continued
Return to Combustion in the RainForest
The Closing Circle