Edexcel Specification focus:
‘The Pressure and Release (PAR) model and the complex inter-relationships between hazard and its wider context.’
Understanding how disasters unfold requires examining the root causes of vulnerability and how they interact with natural hazards to create risk.
The Pressure and Release (PAR) Model
The Pressure and Release (PAR) model is a conceptual framework developed to explain how vulnerability intersects with natural hazards to generate disasters. Rather than viewing a disaster purely as a result of a physical event, the PAR model highlights the complex socio-economic processes that increase the likelihood of serious impacts.
Structure of the PAR Model
The PAR model visualises a disaster as the release of pressure built up by two interacting forces:
Root causes, dynamic pressures and unsafe conditions (representing vulnerability)
A natural hazard event (such as an earthquake, volcano or tsunami)
Disaster occurs when these two opposing forces meet. Therefore, reducing disaster risk involves reducing the pressure from vulnerability as well as preparing for or mitigating the natural hazard.
Components of the Model
1. Root Causes
Root causes are deep-set and persistent factors within a society that create vulnerability.
Root causes: Fundamental political, economic, and cultural processes that shape the distribution of power, wealth, and resources in a society.
These root causes are usually linked to limited access to power, structures, and resources, including:
Poor governance and corruption
Unequal distribution of wealth and land ownership
Colonial legacy and global economic inequalities
Lack of access to education or political participation
Root causes form the base layer of vulnerability — difficult to address, but essential to understand.
2. Dynamic Pressures
These are processes and activities that channel root causes into more visible expressions of vulnerability.
Examples of dynamic pressures include:
Lack of investment in:
Healthcare
Education
Infrastructure
Rapid urbanisation without planning
Population growth and migration
Press freedom and access to information
Weak institutional capacity or disaster preparedness
Dynamic pressures often arise from national or regional decisions and policies, and they convert structural weaknesses into day-to-day unsafe realities for people.
3. Unsafe Conditions
Unsafe conditions are the direct expressions of vulnerability at the local scale, where people live and work.
Unsafe conditions might include:
Living in poorly built housing
High population density in hazard-prone zones
Proximity to a fault line or volcano
Poor sanitation and healthcare access
Livelihoods dependent on fragile environments
These conditions place people at high risk when a hazard strikes. They are the most visible and immediately changeable layer of vulnerability.
4. The Natural Hazard
On the opposite side of the PAR model lies the natural hazard itself. This could be a tectonic event such as:
An earthquake
A volcanic eruption
A tsunami
The hazard represents the physical trigger for a disaster. Its magnitude, duration, and predictability are important, but it only becomes a disaster when it impacts vulnerable people.
Natural hazard: A naturally occurring physical event that has the potential to cause loss of life or damage to property and the environment.
Therefore, without vulnerability, a hazard remains just that — a physical event.
Interrelationships Between Hazard and Wider Context
The PAR model is especially valuable because it shows the interconnectedness of different factors in disaster creation. It shifts the focus from just the hazard to the wider context of vulnerability, highlighting why some communities suffer more than others.
These interrelationships include:
Social inequalities (e.g. gender, class, ethnicity) affecting access to resources and decision-making.
Economic systems that prioritise certain regions or groups over others.
Political structures that may neglect disaster risk management in favour of economic growth or elite interests.
Cultural factors, such as mistrust of authorities or traditional beliefs, that influence how people prepare for or respond to hazards.
By addressing these wider contextual issues, societies can work to reduce vulnerability, making disasters less likely and less severe when hazards do occur.
Using the PAR Model in Hazard Analysis
The PAR model helps geographers, planners, and disaster risk managers analyse why some areas are more disaster-prone than others, even when exposed to similar hazards.
Key applications include:
Identifying intervention points to reduce disaster risk
Prioritising resource allocation for resilience-building
Analysing past disasters to understand vulnerability pathways
Informing policy for sustainable development and hazard mitigation
Summary of the Pressure Pathway
The progression of vulnerability in the PAR model typically follows this layered sequence:
Root causes → drive → Dynamic pressures → produce → Unsafe conditions
When these vulnerabilities are exposed to a natural hazard, the result is a disaster.
Bullet Recap of Key Concepts:
Root causes = deep societal structures (e.g. inequality, poor governance)
Dynamic pressures = translating forces (e.g. lack of training, rapid urbanisation)
Unsafe conditions = immediate local vulnerabilities (e.g. unsafe housing)
Natural hazard = tectonic event (earthquake, volcano, tsunami)
Disaster = outcome when vulnerability meets a hazard
The PAR model encourages proactive, not reactive, disaster management by showing that reducing vulnerability is just as vital as responding to hazards.
FAQ
The PAR model focuses on the underlying social and economic causes of vulnerability, showing how these build pressure that leads to disaster when combined with a hazard.
In contrast, the hazard risk equation is a more general formula used to express risk as a function of hazard, vulnerability, and capacity to cope. It doesn't explore the deeper causes of vulnerability, whereas the PAR model explains why certain groups are more exposed or less able to respond.
So, while both models deal with disaster risk, the PAR model offers a more detailed sociological perspective.
Yes, the PAR model's structure allows it to be applied to any disaster where vulnerability plays a role.
For example, during a pandemic:
Root causes may include poor healthcare infrastructure or systemic inequality.
Dynamic pressures could involve overcrowded living conditions or misinformation.
Unsafe conditions might include lack of sanitation or limited access to vaccines.
Although it was developed for natural hazards, its flexibility means it can be used for broader risk analysis.
Political systems shape how resources, power, and information are distributed, which directly influences vulnerability.
For instance:
Authoritarian regimes may restrict access to information or emergency support.
Corrupt governments might misallocate disaster preparedness funding.
Weak democracies may lack the institutional strength to enforce safety regulations.
Political decision-making also affects long-term investments in healthcare, education, and infrastructure — all vital in reducing vulnerability.
Dynamic pressures are the active processes that translate deeper structural issues into immediate, tangible risks.
For example:
A lack of education (root cause) becomes a dynamic pressure when people cannot read hazard warnings.
Economic inequality (root cause) can lead to rapid urbanisation (dynamic pressure), placing people in informal settlements.
Inadequate planning turns population growth into exposure to danger zones.
These pressures make unsafe conditions more likely to develop.
The PAR model breaks down vulnerability into identifiable layers, making it easier to analyse differences in disaster outcomes.
It helps highlight:
Why a low-magnitude earthquake can be devastating in one country but not in another.
How social and economic inequality increases hazard impacts.
The influence of governance and infrastructure quality on resilience.
This makes it a valuable tool for comparing disaster risk in developed, emerging, and developing countries.
Practice Questions
Question 1 (3 marks)
Outline one way in which root causes can contribute to disaster vulnerability, using the Pressure and Release (PAR) model.
Mark Scheme:
1 mark for identifying a valid root cause (e.g. lack of access to education, unequal land ownership).
1 mark for linking the root cause to increased vulnerability (e.g. unawareness of risks, inability to evacuate).
1 mark for explaining how this contributes to disaster impact when a hazard occurs (e.g. greater exposure or weaker resilience).
Example Answer:
Limited access to education (1) means people may not understand hazard warnings or how to prepare (1), increasing the likelihood of harm during a disaster (1).
Question 2 (6 marks)
Explain how the Pressure and Release (PAR) model helps to understand why the same hazard may have very different impacts in different locations.
Mark Scheme:
1–2 marks for describing the basic structure of the PAR model (e.g. root causes, dynamic pressures, unsafe conditions).
1–2 marks for identifying differences in vulnerability between locations (e.g. governance, infrastructure, poverty).
1–2 marks for explaining how those differences lead to different impacts from the same hazard (e.g. more deaths, damage, or slower recovery).
Example Answer:
The PAR model explains disasters as a combination of vulnerability and hazard. Vulnerability builds through root causes like poor governance, dynamic pressures like lack of planning, and unsafe conditions such as living in hazard-prone areas (1–2). A country with strong institutions and good infrastructure will have lower vulnerability than a country with widespread poverty and weak governance (1–2). As a result, the same earthquake may cause few deaths in one place but thousands in another due to these differing vulnerabilities (1–2).
