How Many People Can the Earth Support? En11ironmenta[Lmpact and Vulnerq Bility
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How Many People Can the Earth Support? En11ironmenta[lmpact and Vulnerq bility. In the minds of many, human Joel E. Cohen years in 1990-1995, an increase of 18 runs out, the price. of coal does not re years. The advantage in life expectancy flect the cost of the collapse of the action is linked to an unprecedented The question "How many people can of .. the more . developed regions over mining community left behind. litany of environmental problems; A the Earth support?" is useful, though the less developed regions fell .from Likewise, market prices need notre grim list prepared by the demographer it is seriously incomplete. It focuses · twenty-six years in 1950-1955 to twelve fleet future consequences of unwanted Paul Demeny in 1991 includes loss of attention on the present and future years in 1990:-1995. In developing re products such .as spent nuclear fuels, topsoil, desertification,. deforestation, numbers,. qualities, activities, and val gions, the absolute number (and the carbon dioxide fron:. power generation, toxic poisoning of drinking water, ues of humans in their relations with proportion) of people who were chron solid wastes from discarded packaging oceanic"pollution, shrinking wetlands, one another and with the Earth. To overgrazi11g, species loss, loss of ically undernourished fell from 941 mil and consumer goods, or ~sl:Jestos, chlor~ wil explain why people are interested in lion around 1970 to 786 million around ofluorocarbons; a)id persistent .pesti-' derness .areas, short(lge of .firewood, this question, I offer an overview of 1990. In Africa, . contrary to the world cides. Assessing ·the costs varies in siltation in rivers and estuaries, en global human population, economy, trend, the absolute number of chroni difficulty, from a relatively easy Gase ctOa€:hment on arable land, dropping environment, and culture.. I then re cally undernourished increq.sed by two like nontoxic solid waste, with a well water tables, erosion of the ozone view some answers to the question and. thirds between 1970 arid 1990. Africa . developed market in some countries, layer, global warming, rising sea lev describe what is involved in answering also had the highest population growth to a relatively hard case like chloroflu els, consumption ofmineral resources, it. Finally, I suggest actionstha:tcould rates during that period -and still does. orocarbon .disposal, apparently with nuclear wastes, anclacid rain. Demeny alleviate some of the problems of pop no present market. complained that ecologists rarely pro ulation, economics, environment, and Economic Growth and Growing third reason that prices are notal vide eno:ugh information to quantify culture. A Economic Disparities. II1 the aggregate ways indicators of human well-being is the relative importance. of these prob The Earth's capacity to support lems in specific locales. More informa people is determined both. by ·natural tion. is needed to evaluate the trade constraints, which some will emphasize, offs among thyse problems, For exam and by human choice, which others will ple; what are the trade-offs . among emphasize. Inthe coming half-century, burying municipal .wa.stes (soil and we ·and our children are less likely to groundwater contamination), incinerc face absolute limits than difficult trade ating them (air pollution), dumping offs-trade-offs among population size. them offshore (marine contamina and economic well-being and environ tion), and reducing them at the source mental quality and dearly .held. values,· (changes in manufacturing and pack~ Foresight and action now might· :qmke aging technology, consumer expecta some of the coming trade-offs easie:r. tfonsamthabits,la:ws·and prices)? I hope to offer a perspective that dif Environmental vulnerability in fers from the views .of those who say creases as humans make contact with that rapid population growth is no the :viruses and other pathogens of problem at all and those who say that previously remote forests and grass: population growth is the only prob lands. The number of people who live lem. A rounded view of·. the facts in coastal cities rapidly approaches should immunize us against both cor one billion. Vulnerability to a rise In nucopians and doomsayers. I give sea levels increases with the tide. ()f more details in my recent book How urbanization. Many People Can the Earth Support?* Past Human Population Culturallmplosion. In recent decades, Population Size and Growth. Two migration~ from rural to urban regions thousand years ago, the Earth had and between countries,as well as busi roughly one quarter of a billion people production of material wealth, the that J1larkets respond to effective~de ness travel, tourism,radio, television, (the population of the United States half-century since 1945. has been a mand, not to human need. Food wm telephones, faxes, the Internet, cas around 1990). By 1650 t~e Earth's·pop~ golden. era of technological·arid eco-. modity prices have dropped by half, settes,. newspapers, an:d magazines, ulation had doubled.· to half a. billion. nomic wonders. For example; .in con while three fourths of a billio.n people have shrunk theworld stage, bringing When the Old World and the New stantprices, with the price in 1990 set in developing countries chronically do cultures into contact and sometimes World began to exchange foods arid equal to 100, totalfood commodity not eat enough (;alories to gr()w nor· into conflict. other resources in a serious way, the prices fell from 196 in 1975 to 85 in mally and walk around, because the In 18QO roughly 1 in50 people lived time r.equired to double thepopulati<m 1992. The.price of petroleum fell froth bottom billion are so poor that they in cities; by 1995 alhtost .1 in 2 did. dropped from more than sixteen cen~ 113 in 1975 to 76 in 1992. Theprice of cannot exercise effective demand in In 195.0 the world had on.e city with turiesto less than .two centuries. The a basket .of thirty-three nonfuel com world commodity markets .. They have more than 10 million. people· (greater human · p0pulation passed one billion modities fell from 159 ·in 1975 to 86 no money to buy food, so they cannot New York). According to a Unitefi arouud1830. The second billion people in 1992. However, timber prices in drive up its price. The extremely poor Nations study, in 1994 the world had were added in only one century, by creased from 62 in 1975 to 112 in 1992. are economically invisible. fourteen cities with more than 10 mil 1930. The next doubling, to four billion, For many economists, the declining As the world's average economic lion people. Of those, only four were took only forty-four years. Until around prices mean that human welfare .isim~ well-being has risen, economic dispar: in. rich countries (in decreasing or 1965, the human population grew .like proving. Many participants in efficient ities between . the. rich and :the poor der: Tokyo, New )'ork, Los Angeles, an interest-bearing accou11t in which the market economies might agree. But have increased: In 19.60 the richest Osaka); the remaining ten were in rate of interestincreased with the bal globaJ ma.rket prices, while useful for countries .with 20 percent of world developing countries '(in decreasing ance in the account. Arourid 1965-1Q70, coordinating eco:qomic activity, are not population earned 70.2 percent of order: Sao Paulo, Mexico City, Shang the. global population growth .rate universally reliable signals of.changes global income, while the poorest coun hai,. Bombay, Beijing, Calcutta, Seoul, reached its all-time peak, then began to in human well-being for at least three tries with 20percent of world popula Jakarta, Buenos Aires; Tianjin). On fall gradually and erratically. Itstill re good reasons. tion eq.rned. 2.3. percent of global in e:very continent, people who vary in mains far above global growth rates ex First, global prices do not reflect the come.. Thus, the ratio of: i~come per culture, language; religion, . values, perienced prior to 1945. depletion of unowned stocks, such as person between the top fifth and the ethnicity, and race-and who share In the lifetime of anyone who is over marine fisheries, the ozone layer, or bottom fifth was .30 to 1 in 1960, In the same space for social, political, and forty, world population .has doubled. water in internationally shared rivers 1970 that ratio was 32 to 1; in 1980, 45 economic activities-have increasingly Never before . the second half of the and aquifers. to 1; in 1991, 60 to 1. In constant.dol come into direct contact.The resulting tWentieth century had any person lived Second, prices need not reflect all lars, the absolute gap between the top frictions are evident in all parts of the through a doubling of world population. environmental and social costs unless fifth and the bottom fifth roughly done world. In· absolute numbers, putting the. first laws and practices bring thosy .costs bled during this period. Between 1970 and 1990 the number billion people on Earth took from the into the costs ofproduction. Environ While the global number and the of women who were economically ac beginning of time to apout1830. Adding mental and social costs may arise from global fraction of chronically under~ tive (that is, working for pay or look the .latest billion took twelve years. extracting natural resources or from nourished people fell over recent ing for paid work) rosefrom37 perlOO In spite of .this. rapid population disposing of :unwanted products .and decades, the share· of global income men to 62 per ·100 men, while the growth, by demographic q.nd nutri~ may be felt locally or globally,.imme earned by the poorest 20 percent of world's population growth rate fell for tional standards average human well diately ot in the future.