The reading notes record thoughts from things I read. 這網誌是我的一些閱讀後的思考和摘要記錄。My website 我的網頁:


The September issue of Scientific American raised an important issue: Crossroads for Planet Earth. The entire issue is dedicated to this theme. The important message is that we have come to a point where what we do in the next 50 years will drastically affect the future of mankind. The significance is that most of us will witness the change within our lifetime. The topics covered were: population, extreme poverty, sustainability of variety of life, energy with less carbon, agriculture, public health and global economy. Every one of them is a well talked about subject affected by short-sighted politics.

While all these subjects are important, I think they all stem from one problem: too many people. Thus I find the article by Joel Cohen on human population most interesting. There are some facts on demographic.
– By 2000, old people outnumbered young people.
– By 2007, urban people will outnumber rural people.
– Since 2003, the median woman had too few or just enough children to replace herself and the father.

In the 21st century, there will be three unique transitions in human history. First, we are the only generation that lived through a doubling of the human population: from 3 billion in 1960 to 6.5 billion in 2005. The peak annual growth rate was 2.1% occurred between 1965 and 1970. Second, the annual growth rate dropped to 1.2% since 1970. This is the first time in history that the population growth rate was resulted from choices by billions of couples to limit the number of children born. Third, there will be an enormous shift in the demographic balance between the more developed regions and the less developed ones. In 1950, the less developed regions had twice the population of the more developed regions, by 2050 the ratio will exceed 6 to 1.

Joel Cohen mentioned four major underlying trends expected to dominate changes in the human population in the next 50 year: that the population will be bigger, slower-growing, more urban and older.

Scientists estimated that our planet could only provide room and food for about 10 billion people. We now have 6.5 billion people. Assuming that fertility will continue its downward trend, the median projection is 9.1 billion people in 2050. If women had on average just one-half child more than assumed, the 2050 population would be 10.6.billion. Furthermore, if 2005 fertility rates remained constant to 2050, population would reach 11.7 billion. Most of us will witness within our lifetime whether there will be a catastrophe in 2050.

Our problems are not just numbers. The urbanization trend means more people will live in cities which are mainly located in arable, fertile lands or coastal lands which are centres of food production. Urbanization of the population will erode the capability of the planet to produce food.

Another problem is the aging of the population. See this projection of the world population by age group. The change is quite obvious.

Urbanization will interact with the transformation of human society by aging. The mobility of younger and better educated workers often weakens traditional kin networks that provide familial support to elderly people. After 2010, most countries will experience a sharp acceleration in the rate of increase of elderly dependency ratio, i.e. the number of people aged 65 and older to the number aged 15 to 64. This will first occur more acutely in the more developed countries, whereas the least developed countries will experience a slow increase in elderly dependency after 2020.

The economic burden imposed by elderly people will depend on their health, on the economic institutions available to offer them work, and on the social institutions on hand to support their care. Because an older person relies first on his or her spouse in case of difficulty, marital status is also a key influence on living conditions among the elderly. Married elderly people are more likely to be maintained at home rather than institutionalized.

The sustainability of the elderly population depends in complex ways not only on age, gender and marital status, but also on the availability of supportive offspring and on socioeconomic status, notably education attainment. Better education in youth is associated with better health in old age. The strategy to improve the sustainability of the coming wave of older people is to invest in educating youth today, including education in those behaviours that preserve health and promote the stability of marriage. Another strategy is to invest in the economic and social institutions that facilitate economic productivity and social engagement among elderly people.

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