Vol. 1(2) SEP 2011 - SAVAP International

Academic Research International
ISSN: 2223-9553
Volume 1, Issue 2, September 2011
CO 2 and energy impacts. And nations in non-tropical regions had higher impacts than nations
in tropical regions, controlling for other factors.
York et al (2003b) again used a modified version of the IPAT equation to examine the
impacts of a whole array of variables on the ecological footprint across most nations. So the
ecological footprint is the dependent variable. They developed a series of analytical models in
which different groups of independent variables are incorporated.
The authors concluded that population size has a roughly proportional effect on the
ecological footprint. A 1% population increase caused a 0.98% increase in ecological
footprint with other factors held constant. Also, the larger the proportion of a nations
population of ages between 15 and 65, i.e. the working age groups, the larger the footprint.
Further, “impacts are higher in nations with more land area per capita, suggesting that
resource availability and/or density influences resource demand”. And, conforming a
conclusion of their other 2003 paper (2003a), impacts also increased the further a nation was
from the tropics.
The authors also draw attention to the fact that the various driving forces have a
multiplicative effect. Now since they also found that increases in GDP consistently lead to
increases in impacts, a key consequence of the multiplicative relationship “is that because of
high levels of consumption in affluent nations, even a slow rate of population growth in these
nations is at least as great a threat to the environment as is a rapid rate of population growth
in less developed nations”.
So quoting from other authors “if the Chinese try to eat as much meat and eggs and drive as
many cars (per capita) as the Americans the biosphere will fry”, the authors point out “that a
slow, but steady, growth in the American population, at current consumption levels, may
equally challenge the biosphere”.
I personally doubt this conclusion. My reason is this. People in developing countries aspire to
the same high standard of living as is presently enjoyed by people in developed, industrial
countries. They wish to attain to our level of affluence, and are moving in that direction in
countries like China. Since population growth is massive in most developing countries, you
have a big increase in both P and A in I=PAT and the multiplicative relationship holds there
as elsewhere.
Shi (2003) studied the impact of population pressure on global CO 2 emissions.
The data was a time-series for 93 countries for the period 1975-1996. For the 93 countries as
a whole, Shi found there was an overall upward trend in emissions during this period (total
increase during the period of 61.18%). Population during the same period grew by 42.82%.
So a 1% rise in population gave a bigger percentage increase in emissions (1.4%) (but see the
criticism of this high elasticity by Cole and Neumayer - the next paper we consider below).
Shi went on to see how country per capita income levels might affect the population - CO 2
emissions
relationship.
Dividing the 93 countries into four income categories, these were the findings in relation to a
one percent rise in population.
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