Determinants of human population growth

Abstract

The 20th century has seen unprecedented growth of the human population on this planet. While at the beginning of the century the Earth had an estimated 1.6 billion inhabitants, this number grew to 6.1 billion by the end of the century, and further significant growth is a near certainty. This paper tries to summarize what factors lie behind this extraordinary expansion of the human population and what population growth we can expect for the future. It discusses the concept of demographic transition and the preconditions for a lasting secular fertility decline. Recent fertility declines in all parts of the world now make it likely that human population growth will come to an end over the course of this century, but in parts of the developing world significant population growth is still to be expected over the coming decades. The slowing of population growth through declining birth rates, together with still increasing life expectancy, will result in a strong ageing of population age structure. Finally, this paper presents a global level systematic analysis of the relationship between population density on the one hand, and growth and fertility rates on the other. This analysis indicates that in addition to the well-studied social and economic determinants, population density also presents a significant factor for the levels and trends of human birth rates.

Tropical forests and the changing earth system

“…Such increases are obviously important, but can only be proximate causes, as human fertility and survival rates are not deterministic, but are greatly influenced by social and economic factors (Collins et al 2001;Lutz & Qiang 2002). Furthermore, the peak growth rate was in the 1960s, and has been declining since, while absolute population increments peaked in the mid-1980s, and have declined since (Lutz & Qiang 2002). Yet the late twentieth and early twenty-first centuries have witnessed the greatest impacts on the Earth system (Crutzen & Steffen 2003;Reid et al 2005).…”

“…Some emphasize the unprecedented expansion of the number of humans, while others emphasize the emergence and spread of particular forms of human social organization. Human numbers have increased at unprecedented rates: globally there has been a tenfold rise over 300 years and a fourfold increase in the twentieth century, to over 6 billion in 2005 (Lutz & Qiang 2002). Such increases are obviously important, but can only be proximate causes, as human fertility and survival rates are not deterministic, but are greatly influenced by social and economic factors (Collins et al 2001;Lutz & Qiang 2002).…”

“…Human numbers have increased at unprecedented rates: globally there has been a tenfold rise over 300 years and a fourfold increase in the twentieth century, to over 6 billion in 2005 (Lutz & Qiang 2002). Such increases are obviously important, but can only be proximate causes, as human fertility and survival rates are not deterministic, but are greatly influenced by social and economic factors (Collins et al 2001;Lutz & Qiang 2002). Furthermore, the peak growth rate was in the 1960s, and has been declining since, while absolute population increments peaked in the mid-1980s, and have declined since (Lutz & Qiang 2002).…”

Identifying the role of conservation biology for solving the environmental crisis

“…Even without direct implementation of these strategies, human population growth is declining and the world population is predicted to stabilize within the next 100 years ( Fig. 3b; Lutz and Qiang 2002). However, projections of human population growth are uncertain, and even the predicted asymptotic population size of 9-10 billion people could be difficult to sustain within biogeophysical limits.…”

“…3a). The causes for this growth are manifold, but related to a shift to sedentary life styles, and increased survival and fertility caused by a combination of increased nutrition and medical expertise (Lutz and Qiang 2002). The world population passed 7 billion people in 2011 and is projected to reach approximately 10 billion people by 2050 (United Nations 2011).…”