The big picture

This video hints at the fact that it is very difficult to measure the carrying capacity for the human population.

On the surface carrying capacity is a very simple concept: the maximum number of species that an environment can support in a given area. All you have to know is what resources the organisms needs and how much of them are in the area. That is pretty straightforward when you are talking about a population of rabbits. You can calculate how much each rabbit needs to eat and drink and how much space they need for a rabbit warren. Then you can assess how much grass, water and space there is and you have the carrying capacity of the area.

Now stop a minute and think about the resources you use in just one day. Start from when you wake up and make a list of everything that you use – the food you eat, the clothes you wear, the drinks you take, the transport you use etc etc. Will that list be the same today as it is tomorrow? Probably not. Could you even begin to calculate your resource needs?

Now look at Figures 1 and 2. Figure 1 shows a poor family dwelling in Kathmandu, Nepal whilst Figure 2 shows a suburban house in the USA. Consider the differences in carrying capacity for an area if everyone in it lived like the people in Kathmandu as compared to everyone living like the people in the USA do. Based on just this fact - the earth could support a lot more Nepalese than Americans.

The human carrying capacity is therefore a bone of contention and it is often calculated for the whole earth not just a region or country. That then presents the problem of “whose living standard do we use to make that calculation?” There are plenty of other reasons human carrying capacity is difficult to calculate too.

Another measure we use to assess human impact and sustainability is the ecological footprint (EF). The EF is a kind of reverse of the carrying capacity. Instead of looking at how many people the land can support the EF looks at how much land is needed to support a particular population.

The EF is a model that is used to determine whether or not we are living within the carrying capacity. Considering we do not know what the carrying capacity is for humans it may seem inappropriate to try and decide whether or not we are living within it.

Carrying capacity

Carrying capacity is a way to assess whether or not a population or species is living sustainably in an area. Does the environment have enough of the necessities of life (food, space and water) to support the population indefinitely without causing environmental damage?

Population numbers vary over time but if the mean population size can be supported then it is within carrying capacity. If population numbers are below carrying capacity will show one of two trends. Certain species (r-strategists) will follow a J-shaped growth curve, they will exceed carrying capacity and there will be a crash that brings numbers back to sustainable levels. Alternatively there are (k-strategists) that follow the s-shaped curve and population growth slows down and stays just below carrying capacity.

Figure 1. How do you define carrying capacity?

International-mindedness

Different countries have different carrying capacities. Have some countries reached theirs?

What determines human carrying capacity?

Compared to other species it is it is much harder to assess carrying capacity for the human population due to the fact that:

• We produce non-biodegradable waste which can cause environmental degradation and reduce the ability of an area to provide resources.
• The resources we use are far more varied and there are necessities and luxuries to take into account.
• Human populations have the capacity to move goods around the world – we can import food from another region if there isn’t enough where we live.
• We employ technology to change the environment.

Waste assimilation

Humans produce waste at a rate above that at which the local environment can assimilate it. Therefore, this becomes an additional factors that must be considered when calculating the carrying capacity for humans. If the environment can not deal with the waste it will cause damage to the complex natural systems and their ability to function effectively. So carrying capacity is linked to the idea that the organisms will not harm the area.

For example the carrying capacity of a plane is directly linked to the number of seats it has, the food and drinks it can carry and its ability to handle the waste that is produced. It is also dependent on the planes ability to function normally. If someone on the plane removed an engine then the plane's function would be compromised. Although this is highly unlikely, the fact remains that the planes ability to support all its passengers is dependent on all its parts working effectively.

Topic 7 looks at global climate change – just one example of how our activities (waste production) are impacting the complex global systems that sustain us. Many people believe that global climate change is clear evidence that we are living above our carrying capacity.

"Climate change, demographics, water, food, energy, global health, women's empowerment - these issues are all intertwined. We cannot look at one strand in isolation. Instead, we must examine how these strands are woven together." - Ban Ki-moon (South Korean statesman and politician; current Secretary-General of the United Nations.)

Subtopic 8.3 deals in more depth with the matter of waste. It is true we are producing more waste and that it is causing a number of problems. However, we are also solving some of those problems with the use of technology.

Range of resources

The range of resources humans use is far more varied than those of other species and that is largely due to the fact that we have necessities and luxuries. Consider everything you use in a day. Make a list of what you consider to be a luxury and what is a necessity. Compare your list with someone else and you are sure to have differences. Food, water and shelter are the necessities used to calculate the carrying capacity for other organisms. But in view of the last section we have to consider sanitation and waste disposal as an integral part of the human carrying capacity. What else is essential – cars, books, computers? Many people would argue that with our current lifestyle all these things are essential.

The amount and range of resources varies enormously between regions too. A subsistence farmer in Amazonia consumes a much smaller amount and range of resources than a commercial farmer in Europe. Therefore a given place can support different human populations depending on the lifestyle of the people that life there. This is seen in the animal kingdom too for instance lions and wildebeest have different lifestyles. Lions are predators and wildebeest are herbivores so a given area has a lower carrying capacity for lions than wildebeest. However, we can still calculate the carrying capacity for both organisms as the range of resources is lower.

Figure 2. One lion to several wildebeest.

Imports

Humans have the ability to move goods around the world. Thus the carrying capacity of a given country is not a simple thing to establish. To get some idea of the scale of global trade check out this website - The Observatory of Economic Complexity - this link is for the UK but you can check out any country you like. According to this site in 2013 the UK imported US$ 615 billion worth of goods. That certainly makes calculating the carrying capacity of the UK very difficult.

It is not only goods and resources that we move around the planet – we move waste around too. For instance, Sweden is now so good at recycling that it no longer has enough trash to keep its waste to energy programme running. It therefore imports 800,000 tons of trash a year. That certainly changes the carrying capacity calculations for Sweden and the countries it imports its waste from. There are numerous MEDCs that export their toxic waste to LEDCs for processing.

Technology

Humans have employed technology to change carrying capacity for many centuries. Do not restrict your view of technology to modern day electronics – it is a much broader concept. Some technological developments have increased the carrying capacity, whereas other developments have reduced it.

Local or global?

Due to the fact that many of these factors vary so much between regions and within regions it is generally accepted that the carrying capacity for the human population is calculated globally. In many cases it is very difficult to decide which area is supporting a particular population.

Is waste disposal a local or global carrying capacity factor? Surely that is a local matter - we produce waste where we are and therefore waste is a local matter. Stop and think a minute. When a plane flies from Italy to Australia – whose problem is the pollution it produces, Italy, Australia or the other countries it passes over? When you eat food imported from halfway across the world whose carrying capacity is being used?

Table 1 highlights some of the impacts of technological advances. Some of the uses of technology are local and the benefits they impart are certainly local. The impacts however are also global. So the actions of one country may impact the carrying capacity of others.

Figure 3. The world is your market place.

What is the Earth’s carrying capacity?

As you can see from the previous sections human carrying capacity is a difficult thing to assess but there have been many attempts made to do so. In 2001 a UN report said the two-thirds of all estimates fell between 4 and 16 billion with a median around 10 billion people. These estimates are dropping as resource depletion and consumption rates continue to rise. The size of the estimate varies depending on the lifestyle chosen to represent the entire human population. Carrying capacity would be lower for a world of people living the middle-class lifestyle. The higher estimates are only possible with much lower resources consumption rates.

Many of the arguments revolve around the models put forward by Malthus and his opponents. Many feel the carrying capacity cannot be applied to the human population because we have the ability to “outwit” environmental constraints e.g. the Green Revolution, high rise living and renewable energy. On the other hand there has to come a point at which the earth can no longer sustain any more people.

Theory of Knowledge

What evidence is there to suggest that humans have reached their carrying capacity?

Ecological footprint (EF)

This video is a very brief introduction to the concept of the EF:

The EF is a model that can be used to estimate the demands that a human population places on the environment. It is the opposite of the carrying capacity in that it is a measure of the amount of land that is needed to support a population. As human populations grow it is becoming increasingly more important to measure the environments capacity to meet our ever-increasing demands.

The EF considers two aspects:

• Biocapacity – this is the earth’s bioproductive land and sea which includes forests, cropland, pastures and fisheries. These areas not only provide food, but they also absorb waste.
• Demand – considers the amount of bioproductive land we need to provide our resources and space for infrastructure and absorb the waste.

Definition

Biocapacity is the boiological capacity of an area/region/country to generate the resources and absorb the wastes of a given population.

International-mindedness

Consider the variation in biocapacity around the world. How do different cultures view this concept?

Before we move on to some facts and figures it is useful for you to know what a hectare (ha) is - 100 m by 100 m or the size of an international rugby field. Rugby may not be familiar to all of you so Figure 1 shows a 400 m running track, something more of you may be familiar with. As you can see the inside of the running track is just over 1ha. You do not have to remember all this but it should help you visualise the size of the area being discussed. For a really good idea of what a hectare looks like go out and measure one out on the ground - 100 m by 100 m.

Figure 1. What is a hectare?

According to WWF’s Living Planet Report 2014 in 2010 the global EF was 18.1 billion global hectares (gha). Big numbers like that are hard to deal with so in more manageable terms than means 2.6 gha/person. That doesn’t sound too much until you consider what is actually available. The amount of productive land available on earth (biocapacity) is only 1.7 gha/person. This is a shortfall of 0.9 gha/person (almost a whole rugby field).

Be Aware

Some of you will notice that these figures are slightly different to the ones given in section 1.4.1. It is not uncommon for figures such as these to vary between authorities, as they are dependent on different methods of calculation. So long as you can remember approximate numbers that is fine.

Aspects of the EF

The EF is made up of different aspects – things that are measured to assess the EF of a person, city, business, country or the planet. Different websites and authorities look at the EF differently and use different categories. If you go to WWF Footprint calculator you will see they assess an individuals footprint using food, home, travel, goods. Earth Day Network uses Global Footprint Network calculator and that looks at food, goods, shelter and mobility. There are many calculators out there - try some for yourself and see what your EF is.

Figure 2. The Ecological footprint.

The EF is very diverse and as with all systems it is best to break it down into its component parts. This is not the only way to breakdown the EF but the next section will use the categories given in Figure 2 as a basis for looking at the demand side of the EF.

Energy, travel and goods

This is a really mixed group of factors and many are interrelated.

• The main issues with energy are to do with what energy source is used to generate electricity, what emissions controls are in place, the use of energy efficient devices and energy saving measures.
• Travel includes public vs. private transport, type fuel used, emissions controls and air travel.
• Goods is very diverse but it includes how many gadgets do people have, built in obsolescence of industry, how often do they replace the devises, etc.

Table 1 shows some of the ways in which energy travel and goods can impact the EF. Make your own table and add more if you can think of more.

Figure 3. Energy saving light bulb.

Settlement & Infrastructure

Settlements and infrastructure takes up large amounts of space. The space taken up by infrastructure and settlements means less space for:

• Natural ecosystems and that can impact biodiversity negatively.
• Crops, pasture and forests – less food can be grown, also less biofuel and other useful crops such as cotton and flax.
• The natural environment to deal with waste products. Forests and other green plants remove carbon from the air during photosynthesis thus countering some of the carbon emissions by the combustion of fossil fuels.

The more space that our settlements and infrastructure takes up the bigger the EF. High-density living saves space as compared to low density. High density can either mean high rise living when there are lots of families living on top of each other or it can mean lots of families living in the same house.

If a single family lives in a detached house then they take up a lot of space and use proportionally more resources (low-density living). If an extended family (parents, grandparents and children) live in the same house they would have a lower EF as a similar amount of resources are being used by more people. The latter is not high-density but it is ecologically more sound than the former.

Food and fiber

Most of our food and some of our fibers come for cropland and pastures. Cropland is used to grow plants, and pastures are for grazing animals. Many animals are no longer fed on pastures; crops are grown and then fed to animals that are kept inside. Think about that in terms of an EF.

Cropland is used for non-food items:

• Corn, sugarcane and sweet sorghum are grown for the production of bioethanol – an alternative to petrol for cars.
• Cotton, flax (linen) and silk (silk-worms) are grown for textiles.
• Pharmaceuticals – many plants have medicinal qualities.
• Tobacco – economic crop in many LEDC’s.
• Tea and coffee – also an economic crop.

So in our lives we use a lot of cropland for our daily needs. However, everybody has to eat so everybody has a food footprint. That can vary considerably depending on your diet – see Table 2.

* Food miles attempts to measure how far food has travelled before you eat it. Calculation of food miles takes in to consideration - ALL the ingredient in the food item - how much energy it takes to get the food to you, how much carbon that generates and removing the waste. Check out your own food miles at foodmiles.com.

As with everything else in ESS this concept has generated a great deal of debate. Many people argue that the following are far worse for your EF.

• Using hot houses and other technology.
• Growing foods out of season.
• Growing foods that are non-native.

For more details check out Shrink That Footprint.

Seafood

Seafood is a slightly narrow term as we eat fish and other items from the sea and freshwater. Some of our intake is from wild catches (many of which are now facing serious problems) and some is from farmed fish. There is a great deal of debate over the relative benefits of wild catch vs. farmed fish. If you are interested the Washington’s Top News (29 September 2015) gives a good overview of the differences between wild and farmed catches.

A major issue with wild catch is that we are eating higher up the food chain. Most of the fish we eat are from the higher trophic levels e.g. Tuna is at T5 (the top of the food chain). That represents a lot of lost energy.

Figure 4. Bluefin tuna - top of the food chain.

Different footprints

The EF is made up of different aspects and you can take any one aspect of the overall EF and look at it separately. In each case the footprint is looking at the portion of the overall footprint that is caused by a particular aspect. The commonest ones are:

• Carbon footprint is the total amount of greenhouse gas (GHG) emissions caused by an individual, city, event, flight, country etc. GHG are emitted through transport, land clearance production and consumption of everything (food, fuel, manufactured goods etc.).
• Water footprint is the amount is water in your EF. This includes the water you use directly (washing and drinking) and indirectly such as the amount of water it takes to grow your food. Some estimates suggest that it takes 800 liters of water to produce one liter of milk.
• Food footprint – you guessed it, a measure the way our food intake impacts the EF. This takes into account the land used in food production (crops, grass, animal feed), the land needed to absorb carbon emissions produced during food production and the sea area for fishing.

There are a number of footprint calculators on the web for all the different aspects of the EF. You could use them as a base to produce a questionnaire about ecological footprints.

Theory of Knowledge

The EF is a model and there are many different types of footprints - carbon, water, food etc. How do we know which model is the best for assessing human impact?

Ecological footprints compared

This video looks at some of the differences in ecological footprints (EF).

The EF can be assessed on a variety of scales from the individual to the country or even the entire global population. There is a considerable amount of variation in the EF of different regions, countries and individuals. EF of a population can be compared to the land area it has available to support (biocapacity). If the EF of a human population is larger than the its biocapacity it indicates that the population is living unsustainably and has exceeded the carrying capacity.

Figure 1. EF against ecological remainder/deficit for 20 selected countries.

Theory of Knowledge

Is it ethically acceptable for some countries to live above their biocapacity by exploiting other countries?

Figure 1 shows the EF plotted against the remainder/deficit of biocapacity. The countries in red are the LEDCs of the world, many of them in Africa. Notice most of these countries are above the zero line – meaning they are living below their biocapacity, they have a remainder. That means they are living below the carrying capacity of the country and living sustainably.

On the other hand the countries in blue are the MEDC and the vast majority of them are well below the zero line meaning they are living in deficit and well beyond the biocapacity of the country. The worst offenders are United Arab Emirates (UAE), Qatar and Bahrain - all of these countries have a biocapacity deficit of a least eight gha/person. That means they need eight gha/person more than they have to support their population. Give this some thought and see if you can work out why these countries are living so far above their environmental means. The MEDCs with a high remainder (+8 gha/person) on their biocapacity are Australia and Canada.

EF and EVS's

Section 8.4.2 dealt with the various aspects of the EF and looked at some of the causes of high and low EFs. It could be argued that a single overarching factor determines the size of the EF of a country and a person - and that it their environmental vale system (EVS). How we view and value the environment effects our life style choices, the food production systems in place, the perceived value of land and how it is used as well as how industry functions.

In subtopic 1.1 we considered three main EVSs ecocentric, anthropocentric and technocentric. Read these sections before continuing, as you need to consider the link between EF and EVS.

Examiner Tip

Questions about the link between EF and EVS can be difficult. There really is no definitive answer and this is one of those areas where you can argue both sides of the case. The use of renewable energy could be seen as ecocentric because they are against any exploitation of fossil fuels but it is also technocentric because renewable energies are a technological solution to the energy supply crisis.

Theory of Knowledge

To what extent does a persons EVS determine their attitude towards their EF?

As you read this next section consider your opinion as to whether the countries are ecocentric, anthropocentric, technocentric or more likely a mix of all of them. Make sure you can use evidence to justify your opinion.

Countries EF compared

As can be seen from Figure 1 there is a wide range in the size of the ecological footprint from the UAE with an EF of 10.68 gha/person to Puerto Rico with an EF of 0.04 gha/person. The reasons for the size of a countries footprint will vary as discussed in section 8.4.2. The following case study looks at why Peru has a low EF.

International-mindedness

Why do different countries have such different cultural attitudes to the impact their population has on the planet?

Do we have a problem?

"The phenomena of human population growth and its impacts are all too apparent; is the ecological community willing to ignore the most pressing social and scientific issue of all time?" - H.R. Pulliam and N M Haddad, 1994 (Professors of ecology).

Theory of Knowledge

Human population growth is a regional problem not a global one. Therefore the social and scientific issues are also regional. To what extend is this statement true?

This video is a great summary of a number of parts of the course and a good introduction to the question – do we have a problem? The quick answer to this question is probably yes. Is there hope for the future? Also, probably yes!

By this stage you have probably worked out that the human population has issues with sustainability. Thesustainability indicators point to problems. We are degrading the environment and consuming finite resources at such a rate that we will exceed the planets carrying capacity. Once we do exceed this carrying capacity (many scientists think we already have) we risk population and social collapse.

The bottom line is this:

• We are using ecosystems un-sustainably.
• We are pushing ecosystems so hard that they are going past the point where we can predict what will happen next (tipping point).
• The poor countries are hardest hit.

Malthusian, Neo-Malthusian and Anti Malthusian theories discuss the consequences of human population growth. The scientific community is well aware of the problem of human overpopulation and there is a great deal on the Internet to raise awareness.

Earth Overshoot Day is the day each year when humans have used all the resources for that year. Earth overshot day is like going to the supermarket to buy a weeks food and eating it all by Wednesday – not a happy situation to be in. It is calculated thus:

(Global biocapacity/world EF) × 365

The worrying thing is that the day is creeping forwards. In 1987 it was December 19, by 2000 it had made it to November 1 and by 2015 (the time of writing this) it was August 13. What this means is that humanity is falling deeper and deeper into ecological debt. Earth Overshoot Day is often depicted as the globe sliding through an hour glass (Figure 1). This image implies that time is running out.

Figure 1. Earth Overshoot Day.

Earth Day is celebrated in April 22 every year. The idea is to raise awareness of the need for environmental protection. Earth Day started in 1970, is celebrated in over 190 countries and is now coordinated by the Earth Day Network.

ESA 100 years (Ecological Society of America) gives an extensive overview of the problems we will face if we are not able to find solutions to our over consumption.

However, amid the doom and gloom there is some optimism as to our future on the planet for example Agenda 21.

Agenda 21

Agenda 21 came out of the 1992 Earth Summit in Rio do Janeiro, Brazil where 178 governments voted to adopt the programme. It is a UN initiative for multilateral organisations, and governments to be executed at local, national and global levels. It has been modified at subsequent UN conferences.

Agenda 21 has four sections, it is a 700 page report so these are just the highlights:

• Section I: Social and economic dimensions to deal with poverty, consumption patterns and health promotion.
• Section II: Conservation and management of resources for development – control of pollution and deforestation, protection of fragile environments, and biodiversity and managing biotechnology and radioactive wastes.
• Section III: Strengthening the role of major group including children, women, NGO’s local authorities and indigenous people and their communities.
• Section IV: Means of implementation – how goods gets done through science technology, education and international institutions.

In terms of ESS Agenda 21 is one of the main initiatives aimed at achieving sustainable development through the involvement of everyone concerned e.g. Governments, NGO's and the people.

Development and evolution of Agenda 21

Since the first Earth Summit in Rio do Janeiro Agenda 21 has evolved. The subsequent developments have been named after the initial location (Rio) and the + indicates how many years have passed since that first initiative.

International-mindedness

Agenda 21 is a global initiative but different countries have different strategies for implementation. What influences the strategies used in different countries?

Examiner Tip

A good local or national case study on an Agenda 21 initiative is good to have. Find one that interests you - preferably local to you but it doesn't have to be.

Is there hope for the future?

Although things look bleak there is hope for the future:

• There is a lot of progress being made towards a more sustainable future. E.g renewable energy.
• We all need to be a little more ecocentric and make better choices for the planet.

Check out the following links:

• Conservation international
• 100 ways you can improve the environment
• EPA

There are many websites that talk about saving the planet. Put together a list of things that you could do to help.