The Human Population

Scientists disagree on Earth’s carrying capacity Every 5 days the global human population increases by roughly 1 million lives 1.8 million infants born for every 800,000 death 400 years ago the human population started to grow (sanitation, and agricultural output) The pattern of growth is exponentially The limiting factor for population growth are:??

A theoritical model of food Thomas Malthus (1798) Human population grow exponentially Food supply growing linearly (increase by fixed amount each year) Concluded that eventually the human population size would exceed the food supply

Many Factors Drive Human Population Changes in population size Fertility Life expectancy Disease Age structure Migration Demographers project that the global human population will be between 8.1 -9.6 billion by 2050. By 2100, it is projected to be between 6.8 billion and 10.5 billion. The dashed lines estimated values.

Changes in population size When demographers look at population trends in individual countries, they take into account Immigration Emigration CBR (number of birth /1000) CDR (number of death /1000) When CBR & immigration are greater than CDR & Emigration growth rate is _?

Changes in population size Global population growth rate = ( CBR -CDR)/ 10 Population growth rate for single nation we need to take immigration and emigration into account. (CBR +Immig.)-(CDR +emigr.)/10 Doubling time =70/ growth arte

Fertility rate Total Fertility Rate (TFR)= estimate of the average number of children that each women in a poulation will bear throughout her childbearing years. e.g U.S. +2 Replacement level fertility . = The TFR requiredto offset the average number of death in a population so that current population size remains stable. Developed countries Replacement level fertility of 2.1 Developing countries (<$3 /person per day) Mortality among young is higher and aTFR of greater than 2.1 is needed to achieve replacement –level fertility. Unlike the CDR and CBR the TFR is not calculate per1000 people. Instead measure birth per woman. The replacement plan is typically is just over 2 children, with 2 being the number of offspring that will replace the parents. When TFR is equal to Rplacement level Fertility and immigration and emigration are equal population within the country are in equal

Life Expectancy Average number of years per life of a new born within particular country Life expectancy is Higher in developed countries. E.g in 2008 for U.S. the life expectancy was 78 years overall Infant mortality Number of death of children under 1 year of age/1000 live birth Child mortality Number of death of children under age of 5 /1000 live birth

Average life expectancies around the world

Infant mortality around the world

Aging & disease The more number of elderly within a country the higher CDR E.g U.S. CDR=8 death /1000 Mexico CDR=5 death /1000 That is due to higher standard of living and higher number of elderly (increase life expectancy) Disease such as HIV which causes AIDS 22 million death between 1990-2007 In Lesotho (South Africa) 23% of adult population are infected with HIV

Approximately 33 million people were living with HIV in 2009, 22 million in sub Saharan Africa

Age Structure Population momentum? The population pyramid illustrate that it takes time for actions that attempts to reduce birth to catch up with a growing population.

Migration Net migration rate= U.S. =3.3 immigrants/1000 people Is the difference between immigration and emigration in a given year /1000 people in a country Positive Net migration means ….? U.S. =3.3 immigrants/1000 people Canada= 7 immigrants/1000 people The movement of people around the world does not affect the total number of people on the planet.

Family Planning As family income increases, people have fewer children. There is a link between higher level education and affluence among females, in particular, and low birth rates. Family planning is regulation of the number or spacing of offspring through the use of birth control. With women option in family planning CBR tend to drop. Many countries such as Kenya and Thailand used family planning campaign to lower its growth rate and TFR As women education increase , more women independency, decrease fertility rate. Developed countries (with high TFR) women have few children than developing countries. Highere reproduction & access to Birth control and envolved in family planning with or without consent of their partner.

Total Fertility rate for educated and uneducated women in six countries. Fertility is strongly related to female education in many developing countries.

Population size and consumption interact to influence the environment. Population size is critical factor in the impact of humans on Earth. Eating, drinking, building homes, …..etc. requires energy resources. Population and economic development are not equally distributed around the world.

The 12 most populous countries in the world China and India are by far the largest nations in the world. Only 3 out of the 12 most populous countries are developed nations. Of Earth 6.8 billion human habitants 5.6 billion live in developing countries, and only 1.3 billion live in developed countries. Although only 1/5 of population live in developed countries they consume half of the world’s energy and resources.

Economic Development Of Earth 6.8 billion human habitants 5.6 billion live in developing countries, and only 1.3 billion live in developed countries. Although only 1/5 of population live in developed countries they consume half of the world’s energy and resources. The average ecological footprint for the world’s 30 wealthiest countries is 6.4 ha (15.8 acers) per capita. Contrast that figure with average ecological footprint for 50 poorest countries: 1.0 ha (2.5 acres) per capita.

Economic Development continue Per capita ecological footprints . Many countries exceed the global average footprint of 2.7 ha per capita. Calculating the per capita ecological footprint for a country provides a way to measure the effect of affluence-money,goods, or property –on the planet.

The IPAT Equation Some countries consume large amount of resources (negative impact on environmental system), while others live much lightly on the land. To estimate the impact of human life styles on Earth scientists developed IPAT equation Impact=Population x Affluence X Technology Impact is the overall environment Population hasd a straightforward effect on impact. 2 people consume twice an amount of 1 Affluence does not have as simple a relationship to impact as population does. One person in developed country has twice the amount impact as a person in developing country. The effect of technology is more complicated e.g CFCs, hybrid car

Material possession L = A typical Thai family R = A typical Japanese family

Last but least!! A relatively small population can have a high environmental impact if its affluence leads to high consumption and extensive use of destructive technology. However, an affluent nation can more easily take measures to reduce its environmental impact through the use of technology that counters pollution and increases the efficiency of resources use. Rural populations tend to have a high local environmental impact but a low global environmental impact.