The relationships between population dynamics, poverty, and climate change are now recognized. This paper summarizes the evidence currently available on these relationships, and their implications for the poorest countries.

The paper begins with a review of the literature on population and depletion of natural resources. This relationship has been hotly debated, with some arguing that human innovation can overcome any resource constraint. The consensus now is that while this may be true of resources that are more fully priced, it is much more difficult to manage environmental common property resources. Efforts to price the use of such resources, notably by imposing a carbon tax, have so far met with very limited success.

While the developed world generated most of the emissions that cause global warming, the brunt of the burden will be borne by the developing world. These burdens are reviewed in Section 2. Section 3 reviews the gains to the poorest countries from fertility decline − to facilitate economic growth and poverty reduction; help mitigate the burdens of climate change that they face; and reduce future increases in global warming that will impact disproportionately on them. Section 4 reviews the evidence on the effectiveness of family planning programs in helping reduce fertility. Natural experiments indicate that they are effective, and have a strong pro-poor impact.

The paper concludes that while the rest of the world wrestles with the political and technological problems of reducing per capita emissions, the poorest countries have at hand the simple and effective means of using family planning programs to improve their circumstances.

# **1.  Population and Natural Resources**

The publication of the study _Limits to Growth_ (Meadows et al 1972) caused much controversy. It summarized the historical trajectory from 1900-1970 of non-renewable natural resources; pollution; population size; food production; and industrial output, and simulated their trajectory from 1970 to 2100. It concluded that sustainable development could not be achieved without curtailing population growth and the use of natural resources.

Others argued that more rapid population growth may help drive economic growth, by spurring technological innovation that can potentially stretch resources indefinitely. Boserup (1965) had argued that rising population tends to induce agricultural innovation and lead to agricultural intensification, allowing greater productivity per unit of land to feed the larger population. Simon (1981, 1996) argued that people and markets innovate in response to potential resource shortages, and therefore the resource base is effectively infinite.<sup>1</sup> Simon’s arguments were supported by studies of the costs of some industrial resources, which were found to have fallen sharply between 1870 and 1957, a period during which there was rapid growth in both population and industrial output (Potter and Christy 1962; Barnett and Morse 1963). For such clearly-priced resources, there are strong private incentives to find innovative ways of managing their use to keep prices down.

The concerns raised by studies forecasting resource depletion receded quickly as technological innovation rapidly raised agricultural productivity and kept the prices of some 2