A framework for the environmental impact of population growth

In 1971 Ehrlich and Holdren wrote and article in Science that would have a huge impact on the understanding of demography and, later, on ecological thought. The name of that article is called “Impact of Population Growth” and presents, in five theorems, a framework for scientists to work on the impact of a growing population on the environment.

Here are those five theorems: 1. Population growth causes disproportionate negative impact on the environment, 2. Problems of population size and growth, resource utilization and depletion, and environmental deterioration must be considered jointly and on a global basis. In this context, population control is obviously not a panacea – it is necessary but not alone sufficient to see us through the crisis, 3. Population density is a poor measure of population pressure, and redistributing population would be a dangerous pseudosolution to the population problem, 4. “Environment must be broadly construed ton include such things as the physical environment of urban ghettos, the human behavioural environment, and the epidemiological environment, 5. Theoretical solutions to our problems are often not operational and sometimes are not solutions.

First theorem

In their first theorem Ehrlich and Holdren say that each human has a negative impact on the environment resulting from agriculture or technology and say that the global impact on the environment can be expressed as an equation where the negative impact on the environment depends on the population and a function which measures the per capita impact.

I = PF

where P is the population and F the per capita impact function. However they add that population and per capita impact are not independent and they demonstrate it using the example of energy consumption in the US: the increase in energy consumption between 1940 and 1969 was of 140%. Under the assumption that an increase in population would account for a proportionate increase in consumption, this would mean that the increase in consumption is explained at 38% of population growth while the actual population growth was 53%. Then, per capita consumption and per capita impact are functions of population size. The authors wrote their equation more precisely by I = PF(P), which means that impact can increase faster than linearly. In the continuity, F(P) can increase or decrease depending on economies of scale or diminishing returns in activities of importance, population size, the threshold effect, and synergism.

Second theorem

In a growing population (70 million more people per year) and a huge proportion of people starving to death because of malnutrition, the high-yield agriculture is a cause of pollution through its negative feedbacks. The authors use the example of the declining fisheries where part of the decline is due to the pollution originating from terrestrial agriculture.

A second source of fisheries decline is of course the overexploitation by the developed countries. The authors say that this is illustrative of the situation in regard of other resources where rapacious and shortsighted behaviour compromises humanity to have a decent existence. They take the United States, their counties, as an example where they account for 30% of the non-renewable resources consumption in the world each year. They add that this is inconsistent with their rhetoric about helping the Third World develop. Indeed they have squandered the world’s rich ores at the detriment of developing countries to do so for their need to grow. Some observers argue that those countries are economically dependent on the use of those resources and that the demand for these resources is too low. It seems to the authors that economists in these countries are as shortsighted as developed ones.

Moreover they add that the relationships between rich and less rich countries must be changed regarding resources.

Finally, if the population growth were halted or reduced and per capita consumption remained the same, we would quickly run out of vital resources.

Third theorem

Their third theorem deals with population and inequitable utilization of world resources. They argue that environmental problems are independent from the population density or, better said, on how the population is distributed over space. The authors say that pressure on resources depends on how many people there are and their pattern of consumption, but in any case on how they are distributed. They add that redistributing population is a costly act and people live where they are because of economic benefits, convenience and agreeable surroundings. Moving population where there are scarce benefits of these patterns would be extremely expensive (think about Las Vegas) and create environmental havoc. Moving people in more habitable places exacerbates another serious problem: the paving-over of prime farmland, the authors say. Whatever is made is actually problematic for two reasons: first because population growth and the aggravation of the distribution problems are correlated, second because population growth drains the financial resources used to combat its symptoms.

Fourth theorem

Ehrlich and Holdren consider the environment as a broad concept. People tend to consider the environment as national parks and large forest. This is not only the case and other consideration must be taken into account. The authors mention the correction of ghettos conditions like in Detroit as well as saving the Great Lakes. Both are imperative. Then, we must pay attention to conflicts within a country (the authors mention within the US) and among countries. Conflicts between countries block progress towards solving problems whereas conflicts among countries can “solve” them once and for all. Finally, we live in an epidemiological environment which deteriorates with malnutrition and crowding – both of which increase with population growth.

Fifth theorem

The authors say that theoretical good solutions to environmental problems are in practice a disaster. Indeed, they say they are too expensive or have a sociological cost. However, they do not say that gains have not been made through technology but they say that even the most enlighted technology cannot make it in front of population growth. Nevertheless, the authors argue that the pseudosolutions pose environmental costs that must be weighted against those they eliminate.