Question

1. What type of population growth has the human population experienced over the last 10,000 years?  Explain how the human population has grown, and what factors are likely responsible for this growth.  What will happen when we reach the carrying capacity for humans?  What factors that limit population growth are likely to result in a slow-down of this growth?

Answer 1

1. Models of Human Population Growth. The logistic equation is a model of population growth where the size of the population exerts negative feedback on its growth rate. As population size increases, the rate of increase declines, leading eventually to an equilibrium population size known as the carrying capacity.

What factors contributed to the world's overall population growth in the last 150 years? advances in medicine, sanitation and nutrition and increased food production has contributed as factors of growth.

The world's human population is growing at an exponential rate. Humans have increased the world's carrying capacity through migration, agriculture, medical advances, and communication. The age structure of a population allows us to predict population growth.

Human Population Growth

Concepts of animal population dynamics can be applied to human population growth. Humans are not unique in their ability to alter their environment. For example, beaver dams alter the stream environment where they are built. Humans, however, have the ability to alter their environment to increase its carrying capacity sometimes to the detriment of other species (e.g., via artificial selection for crops that have a higher yield). Earth’s human population is growing rapidly, to the extent that some worry about the ability of the earth’s environment to sustain this population, as long-term exponential growth carries the potential risks of famine, disease, and large-scale death.

Although humans have increased the carrying capacity of their environment, the technologies used to achieve this transformation have caused unprecedented changes to Earth’s environment, altering ecosystems to the point where some may be in danger of collapse. The depletion of the ozone layer, erosion due to acid rain, and damage from global climate change are caused by human activities. The ultimate effect of these changes on our carrying capacity is unknown. As some point out, it is likely that the negative effects of increasing carrying capacity will outweigh the positive ones—the carrying capacity of the world for human beings might actually decrease.

The 4 factors that affect population growth Includes.

Population growth is based on four fundamental factors: birth rate, death rate,immigration, and emigration.

The main causes of population growth is

Overpopulation is caused by number of factors. Reduced mortality rate, better medical facilities, depletion of precious resources are few of the causes which results in overpopulation. ... In the past fifty or so years, the growth of population has boomed and has turned into overpopulation.

THE CAUSES OF RAPID POPULATION GROWTH

Until recently, birth rates and death rates were about the same, keeping the population stable. People had many children, but a large number of them died before age five.6 During the Industrial Revolution, a period of history in Europe and North America where there were great advances in science and technology, the success in reducing death rates was attributable to several factors: (1) in-creases in food production and distribution, (2) improvement in public health (water and sanitation), and (3) medical technology (vaccines and antibiotics), along with gains in education and standards of living within many developing nations.7 Without these attributes present in many children's lives, they could not have survived common diseases like measles or the flu. People were able to fight and cure deadly germs that once killed them. In addition, because of the technology, people could produce more and different kinds of food. Gradually, over a period of time, these discoveries and inventions spread throughout the world, lowering death rates and improving the quality of life for most people.8

Food Production Distribution

The remarkable facts about the last 150 years has been the ability of farmers to increase food production geometrically in some places. Agricultural practices have improved in the United States in the last two centuries. Much of the world experi-enced agricultural success, especially in the last 50 years. Between 1950 and 1984, for example, the amount of grain harvested worldwide increased from 631 million tons to 1.65 billion tons. This represents a gain of 2.6 times at a time when the world population increased by only 1.9 times.9

In more recent years, the technology has produced a broader variety of techniques: new kinds of seed, chemical fertilizers, pesticides, and more sophisticated machinery. The use of technology has made possible the rapid expansion of agriculture in the United States and other MDCs and LDCs. The use of pesticides in LDCs, for example was expected to increased between 400 to 600% in the last 25 years of the twentieth century. 10

During the past 10 years, the world's food production has increased by 24 per cent, outpacing the rate of population growth.11 However, this increase was not evenly distributed throughout the world. For example, in Africa, food production decreased, while population increased. And world cereal production fell in 1993, according to the FAO, which predicted a food shortage in 20 countries during 1994. 12 However, most experts agree that there is no shortage of food, and that equitable distribution should be sufficient to meet all needs for the future. Lack of money to buy food is the problem of malnourishment. Poverty, in effect translates the world adequacy into national and local shortages. Within households, men and boys have priority for whatever food is available, while women and children, especially girl children are the first to suffer malnutrition. Few resources are available to women, even though they are often responsible the for food supply.13

Improvement in Public Health

People have concerns about surviving daily living, such as meeting basic needs: food, water, and housing. First, access to safe drinking water was related to the incidence of epidemic diseases such as cholera and child survival. Less than 50% of the population had access to safe drinking water before 1990. By 1990, access to safe drinking water had increased by 75 per cent. But between 1990 and 2000 the numbers of people without access to safe water are projected to increase. 14 An increasing number of countries both developed and developing are approaching the limits of sustainable water use based on their own renewable resources.15

Second, the pressure to provide adequate housing increases as the population grows. More than half of the developing world's population will be living in urban areas by the end of the century. This growth outstrips the capacity to provide housing and services for others. In some countries, finding a place to live is hard, especially for women. Some women and children are forced to live in the poorest community where they are open to exploitation and abuse.16

The priorities for getting rid of poverty, improving food supply, ending malnutrition, and providing adequate housing coincide at all points with those required for balanced population growth.

Conquest of Disease

The biggest population story of the last hundred years has been the conquest of disease. Scientists have learned a great deal about the ways to prevent and cure many types of disease. Thus, millions of people who would have died of disease a century ago are more likely to live to old age. The most effective tools in the con-quest of disease have been improved knowledge about nutrition, vaccinations, bet-ter public health practices and the development of new medicines17

In the late 80s, a baby born in Iceland was 32 times more likely to live to the age of one year as a baby born in Afghanistan.18 The major reason for this large difference in survival rate is nutrition. When young children get enough of the right kinds of food, they are likely to live to be adults. In many nations the people know about proper nutrition for young children and adults. Unfortunately, in many LCDs the people lack the money and skills that would allow them to use the knowledge about nutrition they already have. As a result, infant death rates and therefore, overall death rates, remain high in many LDCs. 19

The second most important factor is vaccinations. As far back as 1800, scientists knew how to use vaccines to protect people from infectious disease. Use of that knowledge has reduced the rate of diseases like influenza, smallpox, polio and rubella in MDCs. Again, lack of resources has prevented many LDCs from making similar use of vaccinations to reduce the rate of infectious disease and death rates in their countries. Moreover, vaccines are still not available for some dis-eases-malaria is the most obvious example and the greatest concern in LDCs.20

Third, better public health practices-- the germ theory of disease, discovered by Louis Pasteur in the 1870s clearly demonstrated that a person's health was also a community problem. Sewage dumped into a public water supply could cause dis-ease throughout the community. With this understanding, the science of public health was born. Today, public health measures like waste treatment, water purification, vaccination, and nutritional education are well developed in MDCs. How-ever, public health measures are still absent in many LDCs. As a result, disease continues to spread and cause high death rates.21

And finally, with the advent of new medicines, disease was less of a problem in MDCs because medical science has invented a whole range of new medicines with which to treat everything from infections to pneumonia. In many LDCs, new drugs and medicines are simply not available. 22

As stated earlier, death rates in MDCs have fallen largely because of improved health and medical knowledge and because of better health and medical practices based on that knowledge. Death rates in many LDCs remain high because the money, personnel and facilities needed to put that knowledge into practice are not available.23

Progress in medical science has, therefore, had a great effect on the population of most nations of the world. Nearly everywhere death rates have fallen. At the same time, birth rates, at least in the LDCs, have remained high. This combination of high birth rates and low death rates have led to the population explosion in many countries throughout the world.

The end of the population explosion worldwide will be determined by how much countries invest in family planning efforts to lower fertility and slow down population growth.

Different populations grow at different rates around the world. This depends on how many children families have and the number of years someone is expected to live. The population of many countries in Asia, Africa and Latin America are growing the fastest, especially where large families are still important. These poorer, less developed countries (LDCs) tend to have shorter lives and higher infant death rates. When couples know some of their children may die, they choose to have more. However, many couples wish to limit family size, but lack the information and means to make these choices.

If the Earth reaches its human carrying capacity then it will leads to Developing countries wouldn’t survive and just die out. Charities would try their hardest to save them and Developed countries would probably become Developing.

The human population would just decrease or people just try to increase the capacity.

The Eve of Destruction would probably be on the way too:

• Netherlands, Bangladesh, Polynesia and coastal cities vanished by floods
• Crops turning into deserts which causes world wide famine
• Biodiversity deteriorating; our favourite animals are in threat
• Most natural resources are already used up
• The North Pole becomes sea instead of ice
• More cyclones vanishing tropical places
• Some habited places rise up at least 40*C summer average
• Amazon Rainforest becomes Amazon Desert
• Important animals who once helped us are now gone
• Our greed becomes too much and we can no longer have anything
• Antarctica would be the only hope to live on

However, it’s not too late, you can try to save our environment so our carrying capacity would go up higher. Donating to charity also helps. Remember, the little things could make a big difference and the big things could change the world. And also,  greed is what’s ruining our planet the most, all you need is necessities. Happy planet saving!

Food Supply as Limiting Factor

If there are 12 hamburgers at a lunch table and 24 people sit down at a lunch table, will everyone be able to eat? At first, maybe you will split hamburgers in half, but if more and more people keep coming to sit at the lunch table, you will not be able to feed everyone. This is what happens in nature. But in nature, organisms that cannot get food will die or find a new place to live. It is possible for any resource to be a limiting factor, however, a resource such as food can have dramatic consequences on a population.

In nature, when the population size is small, there is usually plenty of food and other resources for each individual. When there is plenty of food and other resources, organisms can easily reproduce, so the birth rate is high. As the population increases, the food supply, or the supply of another necessary resource, may decrease. When necessary resources, such as food, decrease, some individuals will die. Overall, the population cannot reproduce at the same rate, so the birth rates drop. This will cause the population growth rate to decrease.

When the population decreases to a certain level where every individual can get enough food and other resources, and the birth and death rates become stable, the population has leveled off at its carrying capacity.

Other Limiting Factors

Other limiting factors include light, water, nutrients or minerals, oxygen, the ability of an ecosystem to recycle nutrients and/or waste, disease and/or parasites, temperature, space, and predation. Can you think of some other factors that limit populations?

Weather can also be a limiting factor. Whereas most plants like rain, an individual cactus-like Agave americana plant actually likes to grow when it is dry. Rainfall limits reproduction of this plant which, in turn, limits growth rate. Can you think of some other factors like this?

Human activities can also limit the growth of populations. Such activities include use of pesticides, such as DDT, use of herbicides, and habitat destruction.