A simple question with a very complicated answer. The dispute over the reality of the threat of global warming and the negative effect of carbon emissions has reached a conclusion: Our earth can not indefinitely withstand the environmental pressure it has taken over the past twenty years. The next step is to establish how we, as the United States and a member of the global community, help rectify the problem we have created? Several studies (Bongaarts, John (1992), Birdsall, Nancy (1994), MacKellar, F. et. al. (1995), and Meyerson, Frederick A. B. (1998)) agree there is some positive correlation between population and pollution (in the form of CO2 emissions). I plan to discuss these studies and their findings regarding the influence population growth has on emission levels and future sustainability.
The basic theory relating population and carbon emissions is clearly broken
down in an earlier study (Bongaarts, 1992). This relationship is illustrated
by the following equation: Total carbon emissions (T) = Population size
(P) + GDP/capita (G) + Energy consumption (E) + Carbon intensity (C) + Deforestation
(D). Given this relationship, this study uses the following predictions
for the time until 2100: population size increases (over 200% for developing
countries and over 15% in developed countries), GDP growth rate at 2%-3%,
energy intensity decreases, carbon intensity will stay relatively the same,
and the percentage of deforestation emissions to total emission will fall
from 12% in 1985 to 3% in 2100. According to this study, population growth,
especially in developing countries, will be the most significant factor
in emissions rate. In this study's model, for developing countries population
growth contributes to 48% of emissions increase from 1985-2100. Similarly,
developed countries population growth contributes to 16% of the emissions
increase over the same time frame. These results suggest that population
reduction policies would be most helpful in reducing emissions, especially
in the developing world. Given the earlier equation for emissions (above),
the only way to stabilize emissions (T) is to have the sum of P+C+E+C+D
be equal to zero. Few countries will adopt a policy that reduces per capita
GDP (G), so the sum of P+C+E+D must offset the increase in G. This study
argues that, using the above model and assumptions, that population reduction
should be a significant portion of any reduction policy. This conclusion
coincides with both classical and neo-classical theories (i.e. Solow (1956))
that argue population growth reduces GDP growth, and therefore population
reduction will cause increasing marginal returns and a higher G (and a higher
T, requiring a larger reduction in P). This study perhaps should continue
this research and see how the aforementioned classical/neo-classical theory
holds up when population size is reduced in an effort to reduce pollution.
Another study (MacKellar 1995) takes a close look at the construction of
the models that are used to measure the correlation between population growth
and pollution levels. Specifically, that study compares the advantages of
using the I=PAT equation (I: environmental impact, P: population, A: affluence,
T: technological efficiency) to the I=HAT equation (where H: number of households).
There are schools of thought supporting both models, as I=PAT is more widely
accepted, though it is proven to be limited, where as the I=HAT is a newer,
untested model. Skeptics of the I=PAT model argue that the interaction between
the variables P, A, and T, are different throughout economic theory. Specifically,
there are three schools of thought: Malthusian theory says population growth
decreases affluence and therefore slows technological progress; Boserupian
theory argues population growth drives technological growth and affluence;
the "modernization" argument says that increased affluence slows
population growth and increases technological growth. In contrast, the I=HAT
model allows "H" (number of houses) to act as a proxy for "P"
(population), because this study concludes that the number of houses will
increase faster than the population (in both developed and underdeveloped
countries).
Both models, I=PAT and I=HAT, provide good enough tools for exploring the
relationship between population growth and pollution growth. This study
illustrates that I=HAT and I=PAT models create a generally similar output
for less developed countries but significantly different outputs for more
developed countries. This is important because it suggests the following
explanation: as population growth declines, environmental degradation declines,
though leading to population aging, resulting in larger number of houses,
which in turn increases environmental degradation. What this study ends
up illustrating is that the relationship between fertility decline and environmental
impacts is not as clear as we thought and further research should explore
the possibility of these two models working together. For example, "I"
(Environmental Impact) is likely to be the result of one part I=HAT and
one part I=PAT formulas, as economic consumption choices are made by households
and individuals, so you need to measure the impact of both.
Is reducing the population in developing countries an economically feasible
solution to greenhouse gas reduction? One study (Birdsall, 1994) argues
it is (though there are exceptions). Developing countries contribute 95%
of the world's deforestation carbon emissions, where as they only contribute
20% of fossil fuel carbon emissions. Will fertility reductions reduce the
amount of emissions? Yes…but only marginally--a 9% to 15% reduction
in total fossil fuel emissions by 2050. Even if fertility rates fall, there
is still a larger population to have children and population levels will
not fall unless the mortality rate falls. Therefore, there is no clear answer
to how much growth rates will fall (even if some program were implemented),
and two models are used: standard growth reduction and rapid growth reduction.
When compared to the projected fossil fuel emission reduction correlated
to the growth rate reduction, the study finds that 9%-15% of emissions are
reduced in developing countries by 2050. In comparison, a similar model
projects the effect of population growth reduction on emission reductions
due to deforestation reductions. The study shows that for the period from
1995-2025 (35 years), a scheduled reduction in population growth will result
in a 6.4% reduction in carbon emissions due to deforestation and a 1.6%
reduction in total carbon emissions. The reduction due to slowed deforestation
is lower because of the large variation of forest cover throughout developing
countries (i.e. some developing countries do not have significant forest
cover and will not experience a great surge in emission reductions from
deforestation reductions). This study offers three ways to achieve the necessary
population growth rate reductions: carbon taxes, public spending on family
planning, and educating females on fertility. The cost of a carbon tax would
run approximately $20/ton of carbon emissions (up to 10% of total emissions).
However, family planning would cost between $4-$11/ton and female education
between $3-$9/ton. This study shows not only that population reductions
can help reduce carbon emissions but more importantly, that emissions can
be reduced more cost effectively (in developing countries) by population
growth reductions compared to a carbon emission tax. More importantly, these
population reduction programs in developing countries should be implemented
by developed countries that have the money to fund such a program.
The conclusions of the Birdsall (1994) study have been applied to more modern
issues, such as the Kyoto Protocol. A more recent study (Meyerson, 1998)
similarly argues that population growth reductions can help countries significantly
in reaching their Kyoto emissions standards. The Kyoto protocol requires
that ratifying developed countries must reduce their per capita emissions
to approximately equal their 1990 levels (by 2010). For EU members, this
goal is relatively attainable, as their population growth levels are not
too high and the necessary per capita reduction is generally under or around
10%. According to this study, this is the problem for the U.S. were they
(President Bush) to ratify the Kyoto Protocol at the time of publication
(1998). U.S. assumed population growth rates for the period of 1990-2010
are 17.6%, which is significantly higher than most other countries ratifying
Kyoto. If the protocol were ratified in 1999, the U.S. would have to reduce
its emissions per capita by 26% or greater (approx. 4-5.4 metric tons per
capita), which is an essentially impossible goal for a country whose economy
is tied to the fossil fuel industry. In addition, 33% of U.S. population
growth is attributed to immigration, which in turn drives emission levels.
This study suggests that the Kyoto protocol should reconsider how they penalize
countries that don't meet their reduction goals that suffer from high immigration
levels. In addition, this study points out that "developing" world
will exceed the advisable emissions level by 2000 and countries deemed as
"developing" should not be excluded if emissions stabilization
is truly a goal. However, this conclusion does not consider the cost incurred
by developing countries were they held to the same reduction standards.
Specifically, looking at the environmental Kuznets curve, developing countries
do not have the economic foundation to achieve reductions. The environmental
Kuznets curve argues that opportunity cost incurred by developing countries
to reduce emissions (in the form of foregone GDP growth) is greater than
the opportunity cost of emitting (by growing the economy). Therefore, without
a fuller explanation from the Meyerson study, I side with the Kuznets theory,
and conclude that developing countries should not be held to the standards
of developed countries.
In conclusion, it is clear that each of these studies agree that some percentage
of emissions is due to population growth. It seems that population reduction
is a cost-effective solution to reducing emissions, especially in developing
countries. As mentioned above, this conclusion competes with the theory
behind the environmental Kuznets curve-developing countries need to emit
pollutants to achieve a sustainable GDP level. Therefore, the most sensible
solution would be to have developed countries, with strong economies, fund
the emission reductions programs for developing countries (as suggested
in: Birdsall 1994). In theory this is a good plan, but how likely is this
to happen in the real world? Only time will tell.
Bongaarts, John (1992), "Population Growth and Global Warming"
in Population and Development Review, Vol. 18, No. 2, June 1992,
pp. 299-319.
Birdsall, Nancy (1994) "Another Look at Population and Global Warming",
in United Nations, Population, Environment and Development: Report of
an Expert Group Meeting on Population, Environment and Development,
20-24 January 1992, United Nations, New York, 1994. pp. 39-54.
MacKellar, F. Landis, W. Lutz, C. Prinz and A. Goujon, (1995) "Population
and Households, and CO2 Emissions", Population and Development Review,
Vol. 21, 1995, pp. 849-865.
Meyerson, Frederick A. B. (1998), "Population, Carbon Emissions, and
Global Warming: The Forgotten Relationship at Kyoto", in Population
and Development Review, Vol. 24, No. 1, March, pp. 115-130.