8.4 Human population Carrying Capacity

TOPIC 8.4 HUMAN POPULATION CARRYING CAPACITY

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.

In this unit we will look at how human populations 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.

This unit is a minimum of 4 hours.

Significant Ideas:

Human carrying capacity is difficult to quantify
The EF is a model that makes it possible to determine whether human populations are living withing carrying capacity.

Big Questions:

How useful are the systems approach and the use of models in the study of carrying capacity and ecological footprints?
To what extent are solutions directed at preventing environmental impacts, limiting the extent of the environmental impacts, or restoring systems likely to be most successful in the management of pollution?
Outline contrasting value systems in the development of population policies
How does your own value system compare with others you have encountered with regard to resource use?
Can human use of resources every lead to sustainable development?
How far is it possible for human society to live in balance with the biosphere>?
How do models and/or a systems approach help our understanding of carrying capacity?
Why are some carrying capacities larger than others?
What can be done to reduce carrying capacities?
How do environmental value systems influenced carrying capacities?
What are your views on how best to reduce carrying capacities?
Examine the relationship between carrying capacity and sustainability
How might carrying capacities change in the decades to come. Justify your answer.

Knowledge and Understanding

8.4.U1 Carrying capacity is the maximum number of species, or "load", that can be sustainability supported by a given area.

Explain the concept of carrying capacity.

For a given region, carrying capacity is the maximum number of individuals of a given species that an area's resources can sustain indefinitely without significantly depleting or degrading those resources. Determining the carrying capacities for most organisms is fairly straightforward. For humans carrying capacity is much more complicated. The definition is expanded to include not degrading our cultural and social environments and not harming the physical environment in ways that would adversely affect future generations.

Thomas Malthus believed that thee was finite optimum population size in relation to food supply and that an increase in population above this point would lead to a decline the the standard of living, war, famine and disease.

Esther Boserup believed that people have the resources to increase food production. The greatest resource is knowledge and technology.

8.4.U2 It is possible to estimate the carrying capacity of an environment for a given species; however, this is problematic in the case of human populations for a number of reasons
[Because carrying capacity for human populations is difficult to calculate, it is also difficult to estimate the extent to which they are approaching or exceeding carrying capacity, although environmental indications (Topic 1.4) may help in this respect]

Explain how carrying capacity can be calculated for non-human species.
Discuss why it is difficult to apply the concept of carrying capacity to human populations.

The range of resources used by humans is usually much greater than for any other species
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 Models of a Population Growing and Approaching Carrying Capacity

8.4.U3 EF is the area of land and water required to support a defined human population at a given standard of living. The measure of an EF takes into account the area required to provide all the resources needed by the population, and the assimilation of all wastes.

Define the ecological footprint (EF).

Human beings have an enormous impact on the natural environment, and ultimately on each other. The way we chose to house, clothe, shelter, and meet the needs for vital resources such as food, energy, and water, not only affect the long-term availability of those resources but well-functioning Earth systems such as climate systems, hydrological cycles, nutrient cycles in the atmosphere, hydrosphere, and lithosphere, and the maintenance of a diverse biosphere. But equally significant is the fact that some of our personal and collective choices have an enormous impact on the way human beings interact in cooperative and competitive modes, including the increasingly global search for renewable and non-renewal resources and global efforts to extract benefits from distant locations and in the process limit the extent of environmental degradation.

The Ecological Footprint accounts for the flows of energy and matter to and from any defined economy and converts these into the corresponding land/water area required for nature to support these flows.

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.

Ecological footprints are the hypothetical area of land required by a society, group or individual to fulfill all their resources needs and assimilation of 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 sustainability support given population rather than the population that a given area can sustainably support.

Ecological footprints can be increased by:

greater reliance on fossil fuels
increased use of technology and energy (but technology can also reduce the footprint)
high levels of imported resources (which have high transport costs)
large per capita production of carbon waste (high energy use, fossil fuel use)
large per capita consumption of food
a meat-rich diet

Ecological footprints can be reduced by:

reducing use of resources
recycling resources
reusing resources
improving efficiency of resource use
reducing amount of pollution produced
transporting waste to other countries to deal with
improving country to increase carrying capacity
importing resources from other countries
reducing population to reduce resource use
using technology to increase carrying capacity
using technology to intensify land

Standard of living is the result of the interaction between physical and human resources and can be expressed as:

Standard of living: (natural resources X technology) / population

8.3.U4 EF is a model used to estimate the demands that human populations place on the environment.

Explain how the EF is used to estimate the demands that human populations place on the environment.

The Environmental Footprint measures the types of products or services provided by the global hectares, for example, in terms of goods from crop lands, animal products, fish, forest products, built up areas, and energy and water use. Such analyses identify which areas are placing the greatest strains on ecosystems, and can help set policy priorities. Growth in animal products and energy use, especially of fossil fuels, are two areas that are rapidly increasing these strains.

The Ecological Footprint is not a precise measure of ecological sustainability. While it is perhaps the best estimate to date, it is important to recognize its limitations. In general, the Footprint underestimates the impact of human activities on the biosphere. Any applications of the Footprint methodology must keep this perspective in mind. Because it focuses on renewable resources, the Footprint provides limited information about most non-renewable resources and their impact on ecosystems (with the exception of fossil fuel impacts which it partially addresses)

Factors used to calculate ecological footprint

Bio-productive land: land used for food and materials
Bio-productive sea: sea area used for human consumption
Energy land: land required to support renewable energy instead of non-renewable energy
Built land: land that is used for development of roads and buildings
Biodiversity land: land required to support non-human species
Non-productive land: land: us and deserts, salt marshes, etc.

Factors ignored when calculating the ecological footprint which influence the amount of land a population needs to support itself:

the land or water required to provide and aquatic and atmospheric resources
land or water needed to assimilate wastes other than carbon dioxide
land used to produce materials imported into the country to subsidize arable land and increase yields
replacement of productive land lost through urbanization

If everyone on Earth had the same lifestyle as the ones in the MEDCs, many Earths would be needed to support the global population.

The EF is a model that provides a way round the dilemma of human carrying capacity. Instead of focusing on a given environment and trying to calculate the carrying capacity it provides, it focuses on a given population (with its current rate of resource consumption) and estimates the area of environment necessary to sustainability support that particular population. The size of this area is compared wit the area available to the population, then gives an indication of whether the population is living sustainable and within the carrying capacity provided.

click on the image to calculate your EF

8.4.U5 EFs may vary significantly by country and be individual and include aspects such as lifestyle choices (EVS), productivity of food production systems, land use and industry. If the EF of a human population is greater than the land area available to it, this indicates that the population is unsustainable and exceeds the carrying capacity of that area

Evaluate the link between the EF and EVS/lifestyle choices.

The average US ecological footprint is 50% larger than the average person in most European countries in part because the US has more suburban sprawl, less public transportation, and uses more energy and water per person than most other developed countries. However, the 50% larger footprint does not necessarily mean a 50% better quality of life. For example:

A person who walks or takes public transportation has a smaller footprint than someone who commutes alone fifty miles to and from work in a car (especially if that car only gets 15 miles to the gallon)
A vegetarian has a smaller footprint than someone who eats a lot of meat
A house or office park with a small amount of lawn has a smaller ecological footprint than a house or office park with acres of lawn treated weekly with chemicals and water.

When we look at the footprint of the average person in a MEDC, it is clear that we would exceed the carrying capacity of the earth if in the future, other populations adopted this average lifestyle. Even with the current world population count it is clear that patterns of consumption in MEDCs are not sustainable, and projected future populations make it dramatically less so.

8.4.U6 Degradation of the environment, together with the consumption of finite resources, is expected to limit human population growth

Discuss the link between the EF and sustainability

Clearly, human numbers can not continue to increase indefinitely. Natural resources are already severely limited, and there is emerging evidence that natural forces already starting to control human population numbers through malnutrition and other severe diseases. More than 3 billion people worldwide are already malnourished, and 3 billion are living in poverty; grain production per capita started declining in 1984 and continues to decline; irrigation per capita declined starting in 1978 and continues; arable land per capita declined starting in 1948 and continues; fish production per capita started declining in 1980 and continues; fertilizer supplies essential for food production started declining in 1989 and continues to do so; loss of food to pests has not decreased below 50% since 1990; and pollution of water, air, and land has increased, resulting in a rapid increase in the number of humans suffering from serious, pollution-related diseases

8.4.U7 If human populations do not live sustainable, they will exceed carrying capacity and risk collapse.

Explain how humans can cause the total collapse of environmental life support systems through environmental degradation and excessive consumption of resources.

One of the consequences of this explosive growth in human numbers is that human demands have outrun the carrying capacity of the economy’s natural support systems — its forests, fisheries, grasslands, aquifers, and soils. Once demand exceeds the sustainable yield of these natural systems, additional demand can only be satisfied by consuming the resource base itself. We call this overcutting, overfishing, overgrazing, overpumping, and overplowing. It is these overages that are undermining our global civilization.

World Overshoot Day

8.4.A1 Evaluate the application of carrying capacity to local and global human populations

Applying the concept of carrying capacity to local human populations can be very difficult.

Wide range of resource used
Lifestyle effect resource requirement
Technological development changes resources required and available for consumption
Resources can be imported or recycled

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.

8.4.A2 Compare and contrast the differences in the EF of two countries

The ecological footprint may vary between countries, particularly of different economic development. Explain why two countries of different economic by creating your own exam style resource booklet. This will help you to answer the any EF related question but also allow you to have a more holistic picture of the topic, better understand the resource booklet structure and prepare you for the exam.

Try to cover each of the areas of the EF: Cropland & Footprint, Grazing & Footprint, Forest & Footprint, Fishing Ground & Footprint, Carbon Footprint, and Built-up Land
Try to use a mixture of data, picture evidence, maps, charts and graphs.
Consolidate this by developing 5 questions that would correspond to the resource booklet.

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. 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 CO2 emissions. Fixation of CO2 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.

LEDCs have small ecological footprints as MEDCs have much greater rates of resource consumption. This is partly because MEDCs have higher incomes and the demands for energy resources is high. MEDCs consume a lot of resources as they are wasteful, they also have more waste and pollution. LEDCs are the opposite with lower consumption as people do not have too much to spend. The economy of the country forces them to recycle many resources, however they are developing and they’re ecological footprint is increasing.

Canada (5.4 ha/person) – low productivity from trees as located in high latitudes, large distances to cover by car, wealthy population, heating needed in cold winters and electricity in winter for dark evenings.

Peru (0.9ha/person) – fast growing trees (high NPP), largely vegetarian diet, low car ownership, warm all year round, poor population.

Global Footprint Country Case Studies

8.4.A3 Evaluate how environmental value systems impact the ecological footprint of individuals or populations

Obviously a person's attitude toward the environment is going to influence how they live their life.

Consider how difficult it can be to live sustainably in a country where the norm is to live unsustainably.

People do not want to lower their quality of living, this often outweighs the want to look after then environment.
Individuals in MEDCs generally have a technocentric worldview, which encourages continued high consumption of resources, in the expectation that technology will provide solutions to minimize the environmental impact

Individuals in LEDCs have not only had a historically low consumption of non-renewable resources, but have also adapted environmental value systems that have encouraged working in balance with nature.

Classroom Materials
Carrying Capacity as an Ethical Concept
Comparing Ecological Footprints
Ecological Footprint Project
How Big is your Footprint
Human Carrying Capacity Project Proposal
Population Theorists: Malthus and Boserup
The Human Population--Too Many People

Case Studies
Calgary, Canada
Peru vs Canada

Useful Links
Timeline of US Waste - Rotten Truth
Issues on Kleenex - Kleercut
Recycled Tissue - Greenpeace
Human Carrying Capacity is Dependent on Food Availability
Has The Earth Reached Its Capacity? - How Stuff Works
Reduce, Reuse, Recycle - EPA
10 Ways to Reuse and Recycle - Recycling Facts

In The News
Waste and Recycling News
Global biodiversity down 30 percent in 40 years - Today Tech 14 May 2012
Could Civilization Collapse? - CTC News May 17, 2014

International-mindedness

Sustainability is the responsible use and management of global resources that allows natural regeneration and minimizes environmental damage

TOK

Human carrying capacity is difficult to quantify and contains elements of subjective judgment. it has been claimed that historians cannot be unbiased-could the same be said of environmental scientists when making knowledge claims.

Video Clips

There are over seven billion people currently living on Earth, but with limited resources, when will we run out of room?

When the global population reaches 9 billion people, how will the Earth cope?

Can We Expand Our Carrying Capacity

David Suzuki speaks about world populations and how growth, is ultimately suicidal.

If being alive on Earth were a contest, humans would win it hands down. We're like the Michael Phelps of being alive, but with 250,000 times more gold medals. Today Hank is here to tell us the specifics of why and how human population growth has happened over the past hundred and fifty years or so, and how those specifics relate to ecology.

Our Ecological Footprint: Reducing Human Impact on the Earth

Resource Use (8.4)

How many people can the earth support?
Carrying Capacity of humans?- Live Science
What's your Ecological Footprint?
Explore EF Trends in data

See Topic 1.1 for more information