Population Growth, Ecology, and Poverty

The world’s population of nearly one billion in 1800 has grown to approximately 6.9 billion today, and population projections suggest that the world population will fall somewhere between 8 and 10.5 billion by 2050, depending on changes in national level fertility and mortality rates ( UNPD 2010). Nearly all of the world’s net population growth over the coming 40 years will occur in cities in less developed countries. At the same time, the ecosystems that support people’s livelihoods and wellbeing are being rapidly degraded. The Millennium Ecosystem Assessment examined 24 critical ecosystem services upon which humans depend for their well-being and found that 60% were being degraded or used unsustainably (2005). The impacts of degraded ecosystem services are being disproportionately borne by the poor, are a principal factor contributing to poverty, and are a barrier to achieving the Millennium Development Goals (MEA 2005 ) . Population growth is identifi ed as one of the key indirect drivers of the degradation of these ecosystem services. Population growth itself, however, remains an insuffi cient explanation of relations between population, ecosystems, and poverty. Changes in population composition and population distribution also have important impacts on ecosystems. For example, models show that the aging of populations over the next several decades could result in signifi cant changes in carbon dioxide emissions even in the absence of any technological change (Dalton et al. 2008 ) . In some contexts, the number of households in a society is as important as population size in determining a population’s impact on ecosystems (Liu et al. 2003 ) .