Vulnerability to what?
Whereas the question "vulnerability of what?" refers to the system, function or group which is considered as vulnerable, the question "vulnerability to what?" refers to the drivers which determine vulnerability. In vulnerability research those physical events, phenomena or human activities which adversely affect a function of a system, cause loss and damage or environmental degradation are refered to as hazards. Usually those hazards are understood as something external to the system at risk. The conceptualization of a hazard as external is closely connected to the evolution of hazard research. Assuming a deterministic relationship between nature and disaster it seems plausible to consider a hazard as an external event. However during the last decades the paradigm of social catastrophes gained in importance, pointing to the fact that man-made structures (land use, political power, access to resources, development of technologies) create and enhance vulnerability. Especially the Pressure and release model opens up a new perpective and emphasizes the social, economic and political processes in which vulnerability is generated by spatially and temporally distant root causes, dynamic pressures and unsafe conditions. This paradigmatic shift led to a higher degree of complexity in understanding the causes of natural hazards and defines down the dichotomous conception of internal and external causes. In the ontology we refrain from describing a hazard as "internal" or "external" since this attribute does not add any analytical value and strongly depends on the theoretical background of the respective assessment. Instead several attributes as described below are used to characterize the hazard respectively the driver.
The image illustrates all kind of hazards and vulnerability drivers which are currently covered by our ontology.
Natural drivers are grouped in:
- geological drivers: earthquakes, volcanic eruptions, landslides, tsunamis
- hydrometeorological drivers: heavy rain, cyclones, droughts, (river-)floods, heat waves, snow storms, hail or climate change in general
- and biological drivers.
An adequate classification of social drivers seems much more complicated. So far we distinguish between four branches of social vulnerability drivers:
- Social inequality, which could also be described as uneven inclusion in society. Most vulnerability assessments label social drivers by abstract categories like poverty, inequality, lack of access to resources or political power,
- Governance which includes the political system, a certain policy or policy change,
- War and Conflict as triggering factors of vulnerability (e.g. Bohle XXXX),
- and last but not least anthropogenic impacts which refer to events or phenomena which one the concern the (tangible) environment but are a direct result of human behavior (e.g. technical accidents, inappropriate land use or environmental pollution).
Attributes of drivers
Whereas in engineering and natural sciences a strong focus is put on the description of the hazard according to its type, magnitude, probability of occurance and uncertainty, some vulnerability studies just in a very vague manner adress hazards as a triggering event of vulnerability. For the reader of an assessment and especially practitioners it might be crucial to know whether vulnerability is explicitely measured with regard to a certain event or class of events or whether no concrete assumptions concerning the hazard where made. In our ontology we refer to the latter case as "implicite". Besides the "physical" characteristics hazards differ according to their spatial extent which has strong implications for the exposure of certain regions or groups: e.g. whereas climate change in general describes a global phenomenon, concrete adverse impacts of global warming like extreme weather events or sea level-rise in particular affect people locally in coastal areas or low lying small island countries. Additionally for assessments and their comparison it might be helpful to describe hazards and other vulnerability drivers with regard to their temporal dimension. Turner et al. (2003) propose to distinguish between
- perturbations (in our terminology discrete shocks), which refer to a major spike in pressure going beyond the normal range of variability and are originated beyond the system or location under consideration
- and continuous stressors, which come along with increasing pressure but within the normal range of variability.
As the example above illustrates, hazards can hardly be considered as single, independent events but sometimes coincide with other hazards. Assessments often deal with several of them but it is important to know whether there is any interaction or systematic relationship between them or whether they occur just by incident at the same place. The interactions are of greatest importance in case of cascading events, following a cause-effect-chain (e.g. earthquakes causing tsunamis, fires and technical accidents).
Please note that our ontology separates scales of assessment and scales of driver! We decided on this analytical distinction because both scales are not necessarily congruent and assessments often investigate the vulnerability in a restricted area (e.g. based on administrative boundaries) or refer to a point of time although the perturbation itself is a long term process. To be aware about these different scales might let you think about the appropriate choice of study areas and research designs in general.