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July 2012, Volume 18, Number 3

Global: Population, Climate

The world's population, 7.1 billion in 2012, is growing by 1.2 percent or 85 million a year. Poverty and population growth go together; most of the world's population growth occurs in the poorest countries.

The world's population was 1.6 billion in 1900 and 6.1 billion in 2000. There are several reasons for rapid 20th century population growth, including death rates falling faster than birth rates due to public health improvements. During the 1960s, population growth rates in Kenya and Pakistan topped four percent a year.

Fertility has declined only marginally in countries such as Uganda, where women had an average seven children in the 1970s. With 35 million people, Uganda has a million births a year, twice as many as Germany, which has 82 million residents.

The total fertility rate (TFR) is the average number of children a woman would have if fertility at a point in time remains constant over her lifetime. For example, if the TFR is 2.1, the population of a country will be stable. The UN used fertility levels between 2005 and 2010 as the base for making population projections. It assumed that TFR in developing countries would decline, so that their population would grow from about six billion today to eight billion in 2050 and 8.8 billion in 2100.

If, on the other hand, fertility rates in developing countries remain at today's levels, the population of today's developing countries would be almost 10 billion in 2050 and 26 billion in 2100, highlighting the importance of the declining fertility assumption. However, fertility remains high in many sub-Saharan countries, including population giants such as Nigeria, where women average almost six children.

Fertility has declined much faster in many developing countries recently than in today's industrial countries. For example, US women had an average seven children each in 1800, and it took until 1930 for fertility to decline to 2.1. In Bangladesh, by contrast, fertility declined from about seven children per woman in 1970 to less than three by 2005.

How many people have ever lived on earth? There is no way to answer this question, but demographer Carl Haub uses reasonable assumptions to suggest that the answer may be about 107 billion people born on earth, including 7.1 billion alive today. One reason for the large number of births is that many babies died; by some estimates, half of babies born died in Iron Age France.

There were perhaps 300 million people on earth in 1AD, including perhaps 45 million in the Roman Empire. By 1650, the world's population was about 500 million and by 1800 one billion. (

The demographic dividend combines population dynamics and economic development to argue that developing economies can achieve a powerful economic boost when fertility declines, reducing the number of children and thus dependency and freeing more women to work. If local and foreign investment creates jobs, the result can be an economic surge that pushes economic growth toward 10 percent a year, as in Asian Tiger economies.

The key age group includes those 15 to 29, the so-called youth bulge. If women in this age group have fewer children than their mothers, more can work for wages, providing a demographic dividend that can fuel economic growth. However, if the youth bulge cannot find jobs, and fertility remains high, there is the potential for conflict from frustrated youth.

South Korea provides an example of a demographic dividend. Per capita income rose about six percent a year between 1965 and 1990 as fertility declined from six children per woman to two. By 1980, half of the Korean work force was between 15 and 29, and the dependency ratio fell from 80 per 100 workers to 60.

Climate Change. The UN's Rio+20 meeting in Brazil in June 2012, formally the UN Conference on Sustainable Development (, refocused attention on global warming. The meeting, which attracted 50,000 participants and over 100 heads of state or government, concluded with a 283-paragraph statement that called for developing green energy to combat global warming in fast-growing developing countries.

Administration and waste services, construction, and professional, scientific, and technical services, accounted for almost half of the 855,000 US workers employed in green industries in 2011. The leading occupation of green-industry workers was janitors and cleaners, with 57,000 employees.

The first Rio summit in 1992 produced two landmark treaties, on climate change and biodiversity, that have so far failed to live up to their promises. The 1992 Rio meeting paved the way for the Kyoto Protocol in 1997 to slow global warming.

Critics argue that green energy is too expensive for fast-growing developing countries. They emphasize that 1.3 billion people lack electricity and three million rely on dirty fuels, including dried animal dung, crop residues and wood. They argue that more lives could be saved, and incomes in developing countries would rise faster, if such countries invested in traditional energy sources.

Nature published an article in June 2012 that concluded the earth is near a tipping point, where population growth, climate change and environmental damage will produce irreversible changes. Lead author UCB Professor Anthony Barnosky says that the earth will be hotter in 2070 than ever before in human history, as more carbon dioxide in the atmosphere from the burning of fossil fuels makes the ocean more acidic and less hospitable to sea life.

In the past, ice ages and volcanic activity had impacts including mass species extinction, altered food webs and the emergence of new dominant species. To avoid allowing human activities to produce a new geologic epoch, the so-called Anthropocene for human-influenced change, the paper calls for significant reductions in world population growth and reduced per-capita resource use, more efficient energy use, less reliance on fossil fuels, and stepped-up efforts to protect the parts of earth that have so far escaped human dominance.

The UN Framework Convention on Climate Change in Cancun in December 2010 formally agreed that migration can be an adaptation to climate change and that migrants displaced by climate change are eligible for support from the Green Climate Fund (GCF), which is to begin disbursing assistance in 2020. There is no UN definition of "climate refugee," and many UN organizations are reluctant to use the term "climate migrant." Most plans of action call for GCF funding to help those affected by climate change to adapt and to provide migration assistance.

Brazil. The Amazon rain forest is 55-55; it is 55 percent of the world's rain forest, and 55 percent of the Amazon rain forest is in Brazil. Congo and Indonesia have the next largest rain forests.

In April 2012, Brazil's Congress approved a Forest Code that would give amnesty to landowners who illegally deforested in protected forests in the Amazon before 2008 and allow landowners in the Amazon to reduce obligatory forest cover from 80 percent to 50 percent. Environmentalists say that the new code could lead to another round of deforestation in Brazil.

So-called ruralistas say that the new code is necessary to sustain Brazilian agriculture. Ruralistas also oppose a bill that allows the confiscation of land where internal migrants, usually from the northeast, are found working in slave-like conditions.

In 1965, Brazil had one national forest in the Amazon and one indigenous reserve for Indians. By 2012, half of the Amazon, which contains an estimated 12 percent of the earth's fresh water, has some form of government protection. The Amazon river, the world's second-longest, originates in the Peruvian Andes and carries about 20 percent of the fresh water flowing into the world's oceans, more than the next 10 rivers combined. During the wet season, the Amazon can expand to 120 miles wide, explaining why there are no bridges over the Amazon.

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