• Introduction

    In 2011, the world’s population will surpass 7 billion. While the rate of population growth has slowed in most parts of the world, it still increases by nearly 80 million people every year - the equivalent of adding another U.S. to the world every four years. The number of people on the planet has doubled since 1960, and demographers predict a world population of 9 billion by 2043. (http://www.populationaction.org/Topics/7_Billion/Index.php accessed 27.10.11). However, this figure is based on questionable assumptions about falling fertility rates and the availability of contraception. Nearly half the world’s population - some 3 billion people - is under the age of 25 and entering their childbearing years. Their childbearing choices, and the information and services available to them, will determine how human population growth will look by mid-century. Most countries in the developing world have high fertility rates and are getting younger; some developed countries have low fertility rates and are aging.

    A common argument is that the earth simply cannot sustain 7 billion people. The issue however is complex and is less about the total number, but about how much they consume and where they are concentrated. In monetary terms, most consumption occurs in industrialized nations and globally the worlds richest 20% of people account for 80-90% of total private consumption expenditure. In 2004 the United States accounted for 4.6% of the world's population and 33% of global consumption (http://earthtrends.wri.org/updates/node/236 accessed 12.10.11). Consumption in developing countries is also increasing at a fast pace, particularly in rapidly industrializing economies such as China and India. Refer to the threat section on global resource demand for more information.

    The relationship between biodiversity and human population growth is complex and human interactions with the environment are heavily influenced by economics and culture (Cohen, 1997). For example, when human population growth is high but the Human Development Index (HDI is a measure of development calculated by UNDP on life expectancy, literacy, education and standards of living worldwide) is low, there is a high rate of deforestation, whereas when HDI is high, rate of deforestation has been found to be low despite high population growth (Jha & Bawa, 2006). Surprisingly, high levels of total species number have been found to coincide with high numbers of people (Gaston, 2005), and there is substantially higher human population growth in biodiversity hotspots than other parts of the world (Cincotta et al., 2001). Explanations for this congruence include energy availability and elevation (Luck, 1997), and whilst with appropriate management it may offer an opportunity to facilitate interactions between people and nature, it is also a threat to species conservation (Luck, 1997).

    Human population growth and high density can result in increasing land transformation and influence biodiversity status, and species sensitive anthropogenic change may be lost or decline in abundance. The number of threatened species is predicted to increase on the basis of human population growth alone (McKee et al., 2003). The size of protected areas decreases as human population density increases (Luck, 2007). Average population growth on the borders of protected areas is nearly double the average rural population growth meaning that they attract rather than repel human settlement for the economic opportunities (real or perceived) they provide. Whilst this highlights the value of protected areas for local people, it also highlights a looming threat to protected area effectiveness and biodiversity conservation (Wittemyer et al., 2008).

    Furthermore, research has shown that demographics can have a significant impact on countries’ stability, governance, economic development and the well-being of its people. Countries that lack the means to provide for basic needs of their people face greater risk of instability and conflict. When limited access to family planning contributes to high fertility, it creates a high percentage of young people with fewer economic opportunities. While there is not a direct causal relationship between age structure and conflict, eighty percent of all outbreaks of civil conflict between 1970 and 1999 occurred in countries in which at least 60 percent of the population was under the age of 30 (PPI, 2011). Most countries in the developing world have high fertility rates and are getting younger; some developed countries have low fertility rates and are aging. Since 1946 all great ape range states (except Tanzania) have experienced internal conflicts, lasting years and in some cases decades. Refer to the threat section on war for more information.

  • How important is this threat compared to others?

  • Why is it a threat to great apes?

  • Is human population growth dangerous for all species in the same way?

Compiled and edited 2011 by Kay H. Farmer
Reviewed by Hjalmar Kuehl, Josephine Head and Neba Funwi-Gabga

  • References