Maureen Alan Heston [1991] purchasing-power-parity income measures) and improving

Maureen Cropper and Charles Griffiths paper explains the interaction
of population growth and environmental quality. They stated that the study of interactions between
population growth and the environment has a long history. According to Malthus,
a growing population exerts pressure on agricultural land, forcing the
cultivation of land of poorer and poorer quality. This environmental
degradation (broadly defined) lowers the marginal product of labor and, through
its effect on income, reduces the rate of population growth. The result is an
equilibrium population that enjoys low levels of both income and environmental
quality. In addition their argue is circle around how population growth lead to
an increase in deforestation. With that being stated they come up with an
important question for policy is whether, holding constant per capita in come
and other relevant factors, population pressures have a significant effect on
environmental degradation. Specifically, they examine the effect of population
pressures on deforestation in 64 developing countries. In order to answer these
questions they have used different model, equation and data to explain the
phenomena. First, they refer to the previous research in environmental
economics that has uncovered a relationship between environmental quality,
measured by ambient concentrations of SO2 or particulates, and per capita
income (Gene M. Grossman and Alan B. Krueger, 1991). This so-called
environmental Kuznets curve shows environmental quality worsening up until
about $5,000 of per capita income (using Robert Summers and Alan Heston 1991
purchasing-power-parity income measures) and improving thereafter. Using this
curve it enable them to find a similar relationship for the rate of
deforestation in Latin America and Africa. They estimate this relationship
using pooled cross-section and time-series data for each continent for the
period 1961-1988, including country dummies to capture factors that change
slowly over time, such as the proximity of forests to cities or rivers. Furthermore,
in order to capture the effects of population pressures they include rural
population density and the rate of population growth in the equation as well.
These variables thus shift the Kuznets curve for deforestation. It is thus possible
for a country that is beyond the level of per capita GDP at which environmental
quality begins to improve to have a higher rate of deforestation than a country
that has not yet reached this level of GDP but faces lower population
pressures. This is a simple point, but one that deserves emphasis: the vertical
intercept of environmental Kuznets curves is just as important as the level of
per capita GDP at which the curve peaks. Using the method above they have found
the cause of deforestation which rest on three reasons are highlighted for the
destruction of tropical forests: the desire to convert forest and woodland
areas to pasture and cropland, the harvesting of logs, and the gathering of
fuel wood. Population pressures are emphasized as an underlying cause of all
three sources of deforestation. Population growth, by increasing the demand for
arable land, encourages the conversion of forests to agriculture. Since it is
people living in rural areas who turn to agriculture as a livelihood, one would
expect deforestation to increase with rural population density. Population
growth also increases the demand for wood, both for timber and for fuelwood. Second,
they also use the United Nations Food and Agriculture Organization (FAO)
estimated deforestation rates using a model of population pressure to explain
the linkage between population pressures and deforestation are thought to be so
strong that, in a recent assessment of deforestation in tropical countries. To
conclude their paper they found out that population growth do lead to
environmental degradation and deforestation, but in spite of these grim
predictions, it would be inappropriate to conclude that reducing the rate of
population growth is necessarily the best method of reducing the rate of
deforestation. Deforestation in developing countries is very much a problem of
market failure. They believe that because of property rights are often not
defined or not enforced, the private cost of deforestation is effectively zero.
Put somewhat differently, because people have no right of ownership in the
land, they have no incentive to make efficient land-use decisions. It is this
problem that must be ad dressed, as well as the problems of poverty and
population growth.