CHAPTER 9

Modelling Sustainable Development

Keywords

System (dynamics) Modelling Post-normal science (Human) behaviour

Summary
Study Questions

Summary

Several modelling techniques are available and relevant in sustainability science, amongst others because they are inherently integrating. The construction and use of such models is as much an art as a science.

System dynamics is an important modelling approach. An important first step is establishing a system boundary, as is illustrated with the car system. In natural systems, notions of stocks, flows, positive and negative feedback loops, delays and inertia are key in understanding the dynamic evolution and responses in socio-ecological systems (SES). Also in the social sciences, sustainability issues, it helps to discipline thinking and share and communicate understanding.
Preceding mathematical-formal modelling is the construction of causal loop diagrams (CLDs), which represent the presumed, important cause-effect relationships. Elementary models which can serve as a template to understand dynamic processes, are exponential growth and decline and logistic growth. Particularly in management and social science, some archetypical models of behaviour are useful, such as escalation and eroding goals.
In what has become known as complex system science (CSS), modelling (human) behaviour have become part of understanding dynamics of and interventions in SES. Prominent methodologies, software packages and applications are Cellular Automata (CA)(spatial dynamics), network analysis (interaction) and agent-based models (ABM)(behaviour). In particular in combination with interactive modeling and simulation games, they are helpful in designing policies for sustainable pathways in SES.

Study Questions

Test your understanding of this chapter by reviewing the study questions below.

Question 1. When did the stock of cars in the world start to grow exponentially? What do you call the growth process before this?

Answer:

There are various stocks in the car system that can be distinguished:
car fleet (number of cars); car production/sales and car depreciation
capital stock of car manufacturers; investment in new factories and demolition of old ones
total road network; construction of new roads and demolition of old ones
labourers employed by car manufacturers; hiring new labourers and laying-off of present labourers
amount of pollutants (from car driving) in the air; emission into the air and breakdown (natural, man-made) of pollutants.

The world stock of cars (Figure 9.1a) started to grow exponentially around the 1990s. Before, its increase varied around a linear increase.

Question 2. Discuss briefly two positive and two negative features of the car system as it has developed in the past century.

Answer:

The major positive growth features are the growth in population and in income (Figure 9.1b). Behind these are the perceived and marketized advantages of the car over other transport modes in combination with rapid technological advances.
Negative features are, notably, traffic accidents, air and noise pollution, impact on landscapes and spatial planning, oil depletion and resulting climate change and geopolitical tensions.

Question 3. Explain the difference between a positive and a negative feedback with help of causal loop diagrams. Supply an example for each.

Answer:

A positive loop exists when a variable directly or indirectly changes in proportion with its size. The larger the variable, the larger the change. Examples are population growth when birth rate exceeds death rate, money on a bank account when interest rate exceeds bank fees or a capital stock when investment rate exceeds depreciation rate.
A negative loop exists when a variable directly or indirectly changes in proportion with the distance between the variable and some constant (external or desired) level. The smaller the distance, the smaller the change. Examples are a population growing against external limits (carrying capacity – via outmigration or starvation), a capital stock when depreciation rate exceeds investment rate or decline in pollutant stock or traffic casualties towards some policy target (via policies and technologies).

Question 4. A cup of coffee is cooling down. How would you describe this process, with which stock variable?

Answer:

Cooling down means that energy (heat) flows out into the environment, according to Fourier’s law (flow rate proportional to temperature difference between coffee and environment). This is a process of exponential decline with the amount of heat in the coffee (and the temperature as a proxy indicator of it, provided there is no mass exchange) as the stock variable.

Question 5. Why is the growth of a population sometimes compared with the steering of an oil tanker? What is the characteristic aspect of such a system, given a relevant timescale?

Answer:

System behaviour exhibits inertia because stock levels can usually only be influenced or managed by changing inflows and/or outflows, not directly. The resulting momentum, for instance in a growing population, makes it difficult to rapidly change course – hence the comparison with a large oil tanker. What matters are the relevant time-scales: in driverless cars, even the tiniest inertia can be fatal, whereas climate change policies have to become effective on the scale of decades to prevent grave negative impacts.

Regarding (human) populations: if a population has, as part of the demographic transition, a high net growth rate, it implies that a large part of the population reaches 15-30 years later the age at which they wish to start a family. Thus, one can expect a ‘momentum’ and a new wave of births that cannot easily be prevented.

Question 6. What kind of growth of a variable occurs when the growth rate is dependent on the distance from a certain system state? How do you call such a system state?

Answer:

See previous question. Such a growth process is called a negative or stabilizing feedback process and the system state to which it tends to go is called an attractor (or more specifically for populations a carrying capacity).

Question 7. Mention two positive and two negative loops in the penetration of solar panels in Europe’s electricity systems.

Answer:

Two positive loops are: declining costs with increasing installation (direct) and an expected growth in electricity use (indirect). Two negative loops are: depletion of adequate locations (less solar radiation and/or farther away from users) and storage problems due to a mismatch between (intermittent) supply from PV-installations and demand.

Question 8. What is NIMBY? Which factors play a role with NIMBY in case of renewable energy (Figure 9.8)?

Answer:

NIMBY is the acronym of Not In My BackYard. It denotes the phenomenon that many people are in favour of certain activities or plans unless it affects them directly in their immediate physical environment. It is a well-known phenomenon in planning on-shore wind turbines and (nuclear) power plants: people see the necessity in a larger context but resist the realization in their neighbourhood or region.

An example in the Netherlands is the opposition in Barendrecht, a town near Rotterdam, against an experiment with the storage of carbon-dioxide. A global problem, to which local people contribute a little and for the solution of which they do not wish to bear a disproportionate burden.

Question 9. It is argued that electricity meters should be installed visibly so people use less energy. Sketch the CLD for such an intervention.

Answer:

Appliance user -> sees electricity meter running faster -> becomes aware of use and costs -> switches off or lowers appliance use level -> lower energy use.

Question 10. Apply a possible eroding goal dynamic for the recycling targets of a city. Can you give other examples?

Answer:

The eroding goal archetype, a special case of shifting the burden archetype, describes a situation in which the response to a gap between an (individual or organizational) goal and the actual situation is more to lower the goals than to address the causes. The CLD below is a possible sketch for the eroding goal archetype in a city recycling policies and programs.

Question 11. Governments and corporations often use a comparison with another country, for instance in life expectancy, to motivate policies. Which archetype is this? Give an example in your own life.

Answer:

This is an example of the escalation archetype. A country (or institution or person) sets goals or targets for (the growth of) some variable on the basis of comparison and competition with another country (or institution or person). Behaviour is now determined by the (perceived) difference between the own situation and the situation of the other(s). Which indicator(s) are chosen in this cooperation-competition is of great importance and often part of worldview and negotiation.

Question 12. Why does preferential attachment in the growth of a network make the network more efficient and at the same time more vulnerable?

Answer:

The preferential attachment mechanism in networks is, that if you are rich, the opportunities to become richer e.g. through a strong position in influence and trade networks, are larger than for less rich/connected people. Hence, the neiwork will (start to) exhibit a form of centralization around certain ‘hubs’. For instance, In medieval Europe, such a mechanism gave certain towns an advantage over others because of geographic position, certain manufacturing skills or access to resources. This gave them in turn more resources to expand, in a reinforcing loop. However, it also means that such a network is more vulnerable for disturbances that hit one or more of the central ‘hubs’. This has become evident in e.g. epidemics and terrorist attacks.

Question 13. Which macro-phenomenon emerges in Sugarscape that resembles n observed statistical relationship in the real world (BOX 9.4)?

Answer:

A Pareto-like distribution of wealth, that is, a distribution in which a large portion of wealth is owned by a small fraction of the population. In many situations a distribution of 80% ‘poor’ and 20% ‘rich’ is found, which is called the 80-20 rule or Pareto principle after the Italian scientist Pareto.

Sustainability Science Textbook 2nd Edition

Bert J.M. de Vries

CHAPTER 9

Modelling Sustainable Development

Keywords

Summary

Study Questions

Summary

Study Questions

Question 1. When did the stock of cars in the world start to grow exponentially? What do you call the growth process before this?

Question 2. Discuss briefly two positive and two negative features of the car system as it has developed in the past century.

Question 3. Explain the difference between a positive and a negative feedback with help of causal loop diagrams. Supply an example for each.

Question 4. A cup of coffee is cooling down. How would you describe this process, with which stock variable?

Question 5. Why is the growth of a population sometimes compared with the steering of an oil tanker? What is the characteristic aspect of such a system, given a relevant timescale?

Question 6. What kind of growth of a variable occurs when the growth rate is dependent on the distance from a certain system state? How do you call such a system state?

Question 7. Mention two positive and two negative loops in the penetration of solar panels in Europe’s electricity systems.

Question 8. What is NIMBY? Which factors play a role with NIMBY in case of renewable energy (Figure 9.8)?

Question 9. It is argued that electricity meters should be installed visibly so people use less energy. Sketch the CLD for such an intervention.

Question 10. Apply a possible eroding goal dynamic for the recycling targets of a city. Can you give other examples?

Question 11. Governments and corporations often use a comparison with another country, for instance in life expectancy, to motivate policies. Which archetype is this? Give an example in your own life.

Question 12. Why does preferential attachment in the growth of a network make the network more efficient and at the same time more vulnerable?

Question 13. Which macro-phenomenon emerges in Sugarscape that resembles n observed statistical relationship in the real world (BOX 9.4)?

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