Why there is so much population on earth??

Question

why it is

thanks alll in advance

Answer 1

simply because children as young as 12 are having babies and old folk are living to a greater age/only wars and natural disasters are said to keep the rise in check

Answer 2

Because people are reproducing a little too much, I thought it was pretty self explanatory, but I hope I helped a little.

Answer 3

Because people have kids and if they have more than 1 child then most of the time there kids will have kids and they kids will have kids. So there are 6 billion people on Earth now

40 years ago they where 3 billion people

in another few years there will be 9 billion people

Answer 4

well it is not to the point

Approximately 6.6 billion humans now inhabit the Earth. By comparison, there might be 20 million mallard ducks and, among a multitude of threatened and endangered species, perhaps 100,000 gorillas, 50,000 polar bears, and less than 10,000 tigers, 2,000 giant pandas and 200 California condors. Notably, the human population has grown nearly ten-fold over the past three centuries and has increased by a factor of four in the last century. This monumental historical development has profoundly changed the relationship of our species to its natural support systems and has greatly intensified our environmental impact. Equally amazing are the signs that, in our generation, the human population explosion has begun to abate (Figure 1; note that, here and below, many of the values given are estimates and, after the year 2005, projections). Our numbers are expected to rise by another 50% before reaching a peak late in this century; a decline is likely to follow. What caused this population surge; what caused its reversal; where are we headed; and how might the proliferation of our species affect its future well-being?

Some current demographic trends



Figure 2. Total fertility trajectories of the world and major development groups, 1950-2050 (medium variant). (Source: United Nations Population Division, ''World Population Prospects: The 2004 Revision. Highlights'')Until recently, the growth of our numbers was slow and variable. A pronounced expansion began with the advent of the Industrial Revolution, about two centuries ago. Whereas tens of thousands of years passed before our species reached the one billion mark, around 1800 C.E., it took only 130, 33, 15, 13 and 12 years to add each succeeding billion. This accelerating rate of increase is what is meant by the term population explosion. Around year 1970, population growth reached a maximal rate of about 2% per year—perhaps a thousand times faster than growth in prehistoric times. The annual increment has since dropped from 2.0 to 1.1% (or, as demographers prefer, to 11 per thousand), and it is still going down. Whereas about 90 million individuals were added to the human population at the peak in 1995, our numbers grew by only around 76 million in 2004 (Figure 1). Despite this decline, the world presently takes on a cohort comparable to the population of Germany each year.



Figure 3. Life expectancy at birth for the world and major development groups, 1950-2050. (Source: United Nations Population Division, ''World Population Prospects: The 2004 Revision. Highlights'')Figure 2 shows that fertility is declining with time. It has already declined to below replacement level (i.e., below 2.1 children per woman) in most of the developed countries. World-wide, the average woman currently bears 2.6 live offspring. In some African nations, fertility still exceeds 7 live births. At the other extreme, the average woman in Japan and in much of Europe bears approximately 1.3 live babies.  Correspondingly, population growth rates vary with locale, from more than 3% per year in some African nations to a slightly negative rate (i.e., population loss) in some Eastern European states. Among industrialized nations, the U.S. has the highest rates of both procreation and immigration, giving it the greatest overall population growth rate of any industrialized nation—roughly 1% per year.

The average human life-span has risen from 30-40 years in pre-industrial times to about 65 years today (Figure 3). Longevity is still not much greater than 40 years in Angola but it is more than double that in Sweden and Japan. In developing nations, longevity has sometimes increased by more than half a year in a calendar year. At the same time, the average life-span has been deflected downward in parts of Africa by infectious diseases such as AIDS and by the sociopolitical upheaval that followed the end of communist rule in Eastern Europe.

The demographic transition

The aforementioned historic trends are well understood. Excluding migration, the rate of change of the number of individuals in a population is the difference between birth rate and death rate. The explosion in human population thus reflects the excess of births over deaths fostered by the Industrial Revolution. Until about two centuries ago, birth rates and death rates were both high. Because these two processes were about equal, the population grew slowly and unevenly. For example, human numbers grew at roughly 0.25% per year in 1700 C.E. Soon thereafter, as discussed below, institutional and technical advances caused death rates to fall in one nation after another around the globe. But because birth rates remained high, population growth rates soared, an unintended consequence of the alleviation of human hardship in the modern era. Then, after a few decades of declining death rates, families in those nations developed the inclination and found the means to dramatically limit procreation. As a result, fertility rates fell, often rapidly, to approach the low death rates, and population growth slowed.



Figure 4. The classic stages of the demographic transition. ''Population Bulletin, Transitions in World Population'')A theoretical model called the demographic transition describes the population grows determined by these stages. Figure 4 illustrates its four stages in an idealized fashion. In early times, birth and death rates are high (perhaps both near 5% per year), and there is little sustained growth in the population. In the second stage, death rates decline but birth rates remain high; consequently, the rate of net population growth increases, as indicated in the figure by the shaded area labeled natural increase. Third, birth rates decline to approach the low death rate, causing population growth to subside. Finally, low birth and death rates ensue (each perhaps 1% per year) and growth abates or even becomes negative. The outcome is not a return to the pre-transition state, since the size of the population will have expanded and longevity increased during the demographic transition.

The demographic transition paradigm can be applied both to individual nations and the world population as a whole. The historical prototype is 19th century England. In short order, the transition spread, along with industrialization, to Western Europe and then to the United States. As they modernized in the 20th century, Japan and then certain other Asian nations replicated this transformation. The decades following World War II and the end of the colonial era saw most developing nations embark on this path; now, their death rates are typically at low levels and their birth rates are on the way down. Thus, most nations are currently somewhere in the third stage of their demographic transition and some are in stage four. In fact, the growth rate of the world population in year 2006 was 1.1%, the difference between a birth rate of 2.0% and death rate of 0.9% per year.

In some [[developing nation]s], in which custom may outweigh modern alternatives, the demographic transition has stalled midstream. That is, low death rates (say, 1-2% per year or less) may have been achieved but birth rates linger at 3 to 5% per year. Thus, as in Niger, Mali and Uganda, population growth can exceed 3% per year, making the corresponding doubling time of the population less than 25 years. (Doubling time in years equals 70/growth rate in percent per year. In this example, the doubling time would be 70/3 or 23 years.) This situation can lead to a demographic trap where rapid growth undercuts the very technical, social and economic progress that might otherwise resolve it. The developing nations as a group now have 80% of the world’s population and generate 96% of its growth. The on-going increase of world population can therefore be understood to represent unfinished demographic transitions in diverse pre-industrial societies.

Why death rates have declined

Infectious disease has always been a major cause of human mortality. Over the years, these diseases have included malaria, influenza, tuberculosis, cholera, and a variety of parasitic infections. In particular, childhood diarrhea and respiratory diseases of bacterial or viral origin ravage the young in poor nations; infant mortality can amount to more than 10% of the live births in those settings, compared to less than 0.5% in many industrialized states. The battle against infectious diseases gained force early in the modern era through the development of public health regimes. Thus, long before the era of twentieth-century patient-directed medicine, we learned how to avoid the perils of contaminated drinking water, to drain swamps where mosquitoes harbor the malaria parasite, to immunize the young, to quarantine the infected and to teach public hygiene. (A classical example of an early public health intervention was the introduction of vaccination against smallpox by Edward Jenner more than two centuries ago; this scourge has now been entirely eradicated.) In addition, improved nutrition not only saved lives by itself but also strengthened resistance to infection. These simple preventive strategies were inexpensive and colonists brought them along to protect themselves and their workers. Even today, the transfer of readily-available technology and know-how from more developed countries (MDCs) continues to reduce mortality rates in less developed countries (LDCs).

Why birth rates have declined

Children are naturally loved and valued for themselves. But, especially in traditional (i.e., pre-modern) settings, children are also economic assets: a ready source of capital and security when alternatives are out of reach. Sons are of particular value, since it is they who typically inherit both the family plot and the responsibility for caring for aging parents. For practical reasons, daughters are often less desir

Answer 5

well as the world goes on we start finding new ways to stay alive sooner or later we are gonna live past 200...but the population might go down later because we need money for all ofthe medicines that we are makin for pple to stay alive and the value if the american dollar has gone down alot since the 1980's

but pleez answer my question

http://answers.yahoo.com/question/index;...

there might evn be 10 points in it for you

Answer 6

healthcare and amenities have improved and more people are being born than dying.