Unit+3+-+Human+population,+carrying+capacity+and+resource+use

World population clock: [|http://math.berkeley.edu/~galen/popclk.html]

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The multiple choice section of the paper below is a good comprehension activity based on the writing which is very relevant to this unit of ESS, complete the 30 questions as introductory revision for topic 3



The crossword below was made by students as a revision aid for this unit, could you improve the clues and answers? Have a go at compiling your own crossword for this unit - there are some very good crossword building websites, perhaps you could make a crossword for a friend and they could make you one, you could then benefit from the process and the completion of a crossword, pick an area that you feel you need to revise!



Topic 3: Human population, carrying capacity and resource use (39 hours) **TOK:** What do the models of “natural capital/income” and the “ecological footprint” add to the earlier concepts of “resources” and “carrying capacity”? Is one model any more objective than the other? Is this a good thing? With regard to the terms used, how does the **language** affect our understanding of the concepts? (For example, there is perhaps a sense that “natural capital” is something to be preserved, while “resources” are specifically there for human utilization. Similarly, “ecological footprint” conjures an image of environmental threat from any growing population, whereas “carrying capacity” focuses on the maximum number that a population can reach.)

**3.1 Population dynamics**

3.1.1 Describe the nature and explain the implications of exponential growth in human populations.

3.1.2 Calculate and explain, from given data, the values of crude birth rate, crude death rate, fertility, doubling time and natural increase rate. Crude birth rate: The number of births per 1000 of population born each year Crude death rate: The number of deaths per 1000 of pupulation that dies each year Fertility: Is the number of births per thousand women of child bearing age. Natural increase rate: __ Crude birth rate – crude death rate __ 10 3.1.3 Analyse age/sex pyramids and diagrams showing demographic transition models.
 * Doubling time: ** [[image:DT.png]]



While many of the more economically developed countries (MEDCs) have a declining population size, that of many of the less economically developed countries (LEDCs) is rising rapidly. The position of various countries on the demographic transition model reflects their development stages

3.1.4 Discuss the use of models in predicting the growth of human populations.

This might include computer simulations, statistical and/or demographic tables for LEDCs and MEDCs, age/sex pyramids and graphical extrapolation of population curves.

**3.2 Resources—natural capital**

3.2.1 Explain the concept of resources in terms of natural income.

Ecologically minded economists describe resources as “natural capital”. If properly managed, renewable and replenishable resources are forms of wealth that can produce “natural income” indefinitely in the form of valuable goods and services. This income may consist of marketable commodities such as timber and grain (goods) or may be in the form of ecological services such as the flood and erosion protection provided by forests (services). Similarly, non-renewable resources can be considered in parallel to those forms of economic capital that cannot generate wealth without liquidation of the estate.

3.2.2 Define the terms //renewable//, //replenishable// and //non-renewable natural capital//. 3.2.3 Explain the dynamic nature of the concept of a resource.
 * RENEWABLE NATURAL CAPITAL: ** such as living species and ecosystems, is self-producing and self-maintaining and uses solar energy and photosynthesis. This natural capital can yield marketable goods such as wood fibre, but may also provide unaccounted essential services when left in place, for example, climate regulation.
 * REPLENISHABLE NATURAL CAPITAL ** : such as groundwater and the ozone layer, is non- living but is also often dependent on the solar “engine” for renewal.
 * NON-RENEWABLE ** (except in a geological timescale) forms of natural capital, such as fossil fuel and minerals, are analogous to inventories: any use implies liquidating part of the stock.

Consider how cultural, economic, technological and other factors influence the status of a resource over time and space. For example, uranium, due to the development of nuclear technology, has only recently become a valuable resource.

3.2.4 Discuss the view that the environment can have its own intrinsic value.

Organisms or ecosystems that are valued on aesthetic or intrinsic grounds may not provide commodities identifiable as either goods or services, and so remain unpriced or undervalued from an economic viewpoint. Organisms or ecosystems regarded as having intrinsic value, for instance from an ethical, spiritual or philosophical perspective, are valued regardless of their potential use to humans. Therefore, diverse perspectives may underlie the evaluation of natural capital. Attempts are being made to acknowledge diverse valuations of nature (for example, biodiversity, rate of depletion of natural resources) so that they may be weighed more rigorously against more common economic values (for example, gross national product (GNP)). However, some argue that these valuations are impossible to quantify and price realistically. Not surprisingly, much of the sustainability debate centres on the problem of how to weigh conflicting values in our treatment of natural capital. **TOK:** How can we quantify values such as aesthetic value, which are inherently qualitative?

3.2.5 Explain the concept of sustainability in terms of natural capital and natural income.

The term “sustainability” has been given a precise meaning in this syllabus. Students should understand that any society that supports itself in part by depleting essential forms of natural capital is unsustainable. If human well-being is dependent on the goods and services provided by certain forms of natural capital, then long- term harvest (or pollution) rates should not exceed rates of capital renewal. Sustainability means living, within the means of nature, on the “interest” or sustainable income generated by natural capital. 26 Environmental systems and societies guide

3.2.6Discuss the concept of sustainable development.

The term “sustainable development” was first used in 1987 in //Our Common Future// (The Brundtland Report) and was defined as “development that meets current needs without compromising the ability of future generations to meet their own needs.” The value of this approach is a matter of considerable debate and there is now no single definition for sustainable development. For example, some economists may view sustainable development as a stable annual return on investment regardless of the environmental impact, whereas some environmentalists may view it as a stable return without environmental degradation. Consider the development of changing attitudes to sustainability and economic growth, since the Rio Earth Summit (1992) leading to Agenda 21. **Int:** International summits on sustainable development have highlighted the issues involved in economic development across the globe, yet the viewpoints of environmentalists and economists may be very different.

3.2.7 Calculate and explain sustainable yield from given data.

Sustainable yield (SY) may be calculated as the rate of increase in natural capital, that is, that which can be exploited without depleting the original stock or its potential for replenishment. For example, the annual sustainable yield for a given crop may be estimated simply as the annual gain in biomass or energy through growth and recruitment. See figures 1 and 2.

**Figure 1** total biomass total biomass SY = energy at time //t// + 1 – energy at time //t// **Figure 2** SY = (annual growth and recruitment) – (annual death and emigration) Environmental systems and societies guide 27 Syllabus content

**3.3 Energy resources** ** 4 hours **

3.3.1 Outline the range of energy resources available to society.

3.3.2 Evaluate the advantages and disadvantages of two contrasting energy sources.

Consider one non-renewable (fossil fuels or nuclear) and one renewable energy source.

3.3.3 Discuss the factors that affect the choice of energy sources adopted by different societies.

** This may include availability, economic, cultural, environmental and technological factors. **

**3.4 The soil system**

**4 hours**

3.4.1 Outline how soil systems integrate aspects of living systems.

Emphasize a systems approach. Students should draw diagrams that show links between the soil, lithosphere, atmosphere and living organisms. The soil as a living system should be considered with reference to a generalized soil profile. Studies of specific soil profiles, for example, podsol, are not required. Transfers of material (including deposition) result in reorganization of the soil. There are inputs of organic and parent material, precipitation, infiltration and energy. Outputs include leaching, uptake by plants and mass movement. Transformations include decomposition, weathering and nutrient cycling.

3.4.2 Compare and contrast the structure and properties of sand, clay and loam soils, including their effect on primary productivity. http://pedosphere.ca/resources/bulkdensity/triangle_us.cfm?198,162 Consider mineral content, drainage, water- holding capacity, air spaces, biota and potential to hold organic matter, and link these to primary productivity.

3.4.3 Outline the processes and consequences of soil degradation.

Human activities such as overgrazing, deforestation, unsustainable agriculture and irrigation cause processes of degradation. These include soil erosion, toxification and salinization. Desertification (enlargement of deserts through human activities) can be associated with this degradation.

3.4.4 Outline soil conservation measures.

3.4.5 Evaluate soil management strategies in a named commercial farming system and in a named subsistence farming system.

**3.5 Food resources** **6 hours**

3.5.1 Outline the issues involved in the imbalance in global food supply.

Students should appreciate the differences in food production and distribution around the world, including the socio-political, economic and ecological influences on these.

3.5.2 Compare and contrast the efficiency of terrestrial and aquatic food production systems.

Compare and contrast these in terms of their trophic levels and efficiency of energy conversion. There is no need to consider individual production systems in detail. In terrestrial systems, most food is harvested from relatively low trophic levels (producers and herbivores). However, in aquatic systems, perhaps largely due to human tastes, most food is harvested from higher trophic levels where the total storages are much smaller. Although energy conversions along the food chain may be more efficient in aquatic systems, the initial fixing of available solar energy by primary producers tends to be less efficient due to the absorption and reflection of light by water.

3.5.3 Compare and contrast the inputs and outputs of materials and energy (energy efficiency), the system characteristics, and evaluate the relative environmental impacts for two named food production systems.

The systems selected should be both terrestrial or both aquatic. In addition, the inputs and outputs of the two systems should differ qualitatively and quantitatively (not all systems will be different in all aspects). The pair of examples could be North American cereal farming and subsistence farming in some parts of South-East Asia, intensive beef production in the developed world and the Maasai tribal use of livestock, or commercial salmon farming in Norway/Scotland and rice-fish farming in Thailand. Other local or global examples are equally valid. Factors to be considered should include: see guide

3.5.4 Discuss the links that exist between social systems and food production systems. This could be illustrated through the use of examples, such as: see guide []

**3.6 Water resources** **3 hours** 3.6.1 Describe the Earth’s water budget.

Only a small fraction (2.6% by volume) of the Earth’s water supply is fresh water. Of this, over 80% is in the form of ice caps and glaciers, 0.6% is groundwater and the rest is made up of lakes, soil water, atmospheric water vapour, rivers and biota in decreasing order of storage size. Precise figures are not required.

3.6.2 Describe and evaluate the sustainability of freshwater resource usage with reference to a case study.

Irrigation, industrialization and population increase all make demands on the supplies of fresh water. Global warming may disrupt rainfall patterns and water supplies. The hydrological cycle supplies humans with fresh water but ** we are withdrawing water from underground aquifers and degrading it with wastes at a greater rate than it can be replenished. Consider the increased demand for fresh water, inequity of usage and political consequences, methods of reducing use and increasing supplies. A case study must be explored that covers some of these issues and demonstrates either sustainable or unsustainable water use. **

3.6.1 Describe the Earth’s water budget.

Only a small fraction (2.6% by volume) of the Earth’s water supply is fresh water. Of this, over 80% is in the form of ice caps and glaciers, 0.6% is groundwater and the rest is made up of lakes, soil water, atmospheric water vapour, rivers and biota in decreasing order of storage size. Precise figures are not required.

3.6.2 Describe and evaluate the sustainability of freshwater resource usage with reference to a case study.

Irrigation, industrialization and population increase all make demands on the supplies of fresh water. Global warming may disrupt rainfall patterns and water supplies. The hydrological cycle supplies humans with fresh water but we are withdrawing water from underground aquifers and degrading it with wastes at a greater rate than it can be replenished. Consider the increased demand for fresh water, inequity of usage and political consequences, methods of reducing use and increasing supplies. A case study must be explored that covers some of these issues and demonstrates either sustainable or unsustainable water use.

3.7.1 Explain the difficulties in applying the concept of carrying capacity to local human populations.
 * 3.7 Limits to growth**

By examining carefully the requirements of a given species and the resources available, it might be possible to estimate the carrying capacity of that environment for the species. This is problematic in the case of human populations for a number of reasons. The range of resources used by humans is usually much greater than for any other species. Furthermore, when one resource becomes limiting, humans show great ingenuity in substituting one resource for another. Resource requirements vary according to lifestyles, which differ from time to time and from population to population. Technological developments give rise to continual changes in the resources required and available for consumption.

Human populations also regularly import resources from outside their immediate environment, which enables them to grow beyond the boundaries set by their local resources and increases their carrying capacity. While importing resources in this way increases the carrying capacity for the local population, it has no influence on global carrying capacity. All these variables make it practically impossible to make reliable estimates of carrying capacities for human populations.

3.7.2 Explain how absolute reductions in energy and material use, reuse and recycling can affect human carrying capacity.

Human carrying capacity is determined by the rate of energy and material consumption, the level of pollution and the extent of human interference in global life-support systems. While reuse and recycling reduce these impacts, they can also increase human carrying capacity.

**3.8 Environmental demands of human populations** **6.5 hours**

3.8.1 Explain the concept of an ecological footprint as a model for assessing the demands that human populations make on their environment.

The ecological footprint of a population is the area of land, in the same vicinity as the population, that would be required to provide all the population’s resources and assimilate all its wastes. As a model, it is able to provide a quantitative estimate of human carrying capacity. It is, in fact, the inverse of carrying capacity. It refers to the area required to sustainably support a given population rather than the population that a given area can sustainably support.

3.8.2 Calculate from appropriate data the ecological footprint of a given population, stating the approximations and assumptions involved.

Although the accurate calculation of an ecological footprint might be very complex, an approximation can be achieved through the steps outlined in figures 3 and 4. The total land requirement (ecological footprint) can then be calculated as the sum of these two //per capita// requirements, multiplied by the total population. This calculation clearly ignores the land or water required to provide any aquatic and atmospheric resources, assimilate wastes other than carbon dioxide (CO 2 ), produce the energy and material subsidies imported to the arable land for increasing yields, replace loss of productive land through urbanization, and so on.

**Figure 3** //per capita// land requirement for food production (ha) **Figure 4** //per capita// land requirement for absorbing waste CO 2 from fossil fuels (ha) //=// //= see guide p 33//

3.8.3 Describe and explain the differences between the ecological footprints of two human populations, one from an LEDC and one from an MEDC.

Data for food consumption are often given in grain equivalents, so that a population with a meat-rich diet would tend to consume a higher grain equivalent than a population that feeds directly on grain. Students should be aware that in MEDCs, about twice as much energy in the diet is provided by animal products than in LEDCs. Grain production will be higher with intensive farming strategies. Populations more dependent on fossil fuels will have higher CO 2 emissions. Fixation of CO 2 is clearly dependent on climatic region and vegetation type. These and other factors will often explain the differences in the ecological footprints of populations in LEDCs and MEDCs.

3.8.4 Discuss how national and international development policies and cultural influences can affect human population dynamics and growth.

Many policy factors influence human population growth. Domestic and international development policies (which target the death rate through agricultural development, improved public health and sanitation, and better service infrastructure) may stimulate rapid population growth by lowering mortality without significantly affecting fertility. Some analysts believe that birth rates will come down by themselves as economic welfare improves and that the population problem is therefore better solved through policies to stimulate economic growth. Education about birth control encourages family planning. Parents may be dependent on their children for support in their later years and this may create an incentive to have many children.

Urbanization may also be a factor in reducing crude birth rates. Policies directed towards the education of women, enabling women to have greater personal and economic independence, may be the most effective method for reducing population pressure.

3.8.5 Describe and explain the relationship between population, resource consumption and technological development, and their influence on carrying capacity and material economic growth.

Because technology plays such a large role in human life, many economists argue that human carrying capacity can be expanded continuously through technological innovation. For example, if we learn to use energy and material twice as efficiently, we can double the population or the use of energy without necessarily increasing the impact (load) imposed on the environment. However, to compensate for foreseeable population growth and the economic growth that is deemed necessary, especially in developing countries, it is suggested that efficiency would have to be raised by a factor of 4 to 10 to remain within global carrying capacity.