See figure to right - the curve sweeping upwardsis the exponential growth curve.
Darwin used this information to helpdevelop his theory of natural selection by assuming that this situationoccurs for all living organisms, not just humans!!
So, does it work? Consider thatina typical day, 35,000 humans starve to death around the world.Most in developing countries.
What is the Current Population of the Earth?
The current population of the earthis about 6.2 Billion people! This ismore humans alive than at any time in human history.
To see how fast the world populationis growing, click onthis to see a clock of human population growth.
For interesting facts on worldwidepopulation growth, and the factors affecting it, clickhere. Recommended web site!!
For even more interesting facts, clickhere. The Population Reference Bureauhas some of the best information on human population growth of anywhere!
What is Current Net Reproductive Rate of Humans Worldwide?
The currentpercentage increase in the human population (as of 2000) is about 1.3%,or 0.013 per year.
If we multiply this, as shown above,by the current population, we get the increase in humans per year:
0.013 x 6.2 B = 80,600,000 new people per year, or 80.6 million new humanseach year!!
That is the equivalent of 2.5 California'sper year, or 1 new Germany per year. It is 1.6 million people perweek (one New Mexico per week), or 221,000 people per day (one Charlotte,NC added per day!).
An astounding growth rate, even thoughthe net reproductive rate is actually quite small. But growth isnot evenly distributed around the world. Certain countries are growingfaster than others, while some are actually losing growth (deaths and emigrationexceed births plus immigration - Albania is an example).
Why the Increase in Human Population Growth Rates ThisCentury?
Remember, only two things affect populationgrowth: births and deaths. So, have these changed?
Birth rates: have been constant for many years at about 22 babies/1000people/year
Death rates: have declined dramatically due to more food, less disease,more social structure
Death Rates in 1900: 20/1000/year NetReproductive Rate 1900: 22-20/1000 = 0.002 or 0.2%
Death Rates in 2000: 9/1000/yearNet Reproductive Rate 2000: 22-9/1000 = 0.013 or 0.13%
Due to decline in death rates, r for humans has risennearly 6 fold!!!
Some Representative Growth Ratesfor Countries Around the World
Consider this statistic: 90% of all world population growth occurs in developingcountries!!
Go to this website to see net reproductive rates for all countries:
Net ReproductiveRates
World1.3%
More DevelopedCountries0.1%
Less DevelopedCountries1.6%
Africa2.9% !!
Liberia3.1% !!!!!
Canada0.3%
United States0.6% (much of it immigration, about 1/3!)
Mexico1.9%
Europe-0.1% (population is declining!!)
England0.1
France0.4
Latvia-0.6%
You can determine the population doublingtimes for the world and countries by dividing 69.3 by the growth rate.For example, if the world growth rate is 1.3%, then the time it takes todouble the population is:
69.3/1.3 = 53 years
Thus, if things don't change, the worldpopulation could rise to 12.4 Billion in the year 2055!! When I wasborn, the population was about 2 Billion in 1952. It is now 50 yearslater, and the population is 6.2 Billion. That is nearly a tripling!!Why? The world population growth rate was much higher in the past50 years than it currently is. When I was born, the population growthrate was over 2% per year, and the doubling time was down to 42 years!!
Why Do Growth Rates Differ Between Countries?
Demographics!! If you have moreyoung people, then you have more opportunity to make babies!! Developingcountries have more young people than developed ones. Why?In developed countries, couples wait longer to have babies, and, they tendto have fewer per couple. In undeveloped countries, children areproduced sooner, and couples have larger families than in developed countries.
In Mexico, 50%of the population is age 15 or younger!
In the UnitedStates, only about 25% of the population is this young.
What Can Be Done to Control Population Growth?
There are two simple ways to lowerpopulation growth: increase the number of deaths, or, decrease the numberof births. I think for most of us, we would opt for the latter solution.How to do that?
1. Family Planning - have babies ata later age, use contraception (birth control), limit number of babiesper family
2. Education - the best correlateof lowering the number of babies per family is the educational status ofthe females
The more education the females have, the more control they have over theirreproductive lives
3. Better social security - in developingcountries, large families are a form of social security. If povertycan be reduced,
then the need for large families is lowered (hard to do though!)
The Future - How Large Will the Population Become?
In your lifetime, the population couldapproach or exceed 14 Billion people. Can we feed that many?Not likely. Is there enough water for that many? Probably not.Enough habitat? Probably not.
So, what will the population stabilizeat? Best guesses are between 7-10 Billion people. Will theworld still be a great place with that many people? Unlikely.
There is a great need to reduce populationgrowth, starting now!! You can help a great deal.
1. Have only 2 children per family.That way, population growth is reduced to essentially zero.
2. Wait till a later age to have children.
