A risk framework
When estimating the impact of conflict, we will apply the framework utilized by impacts and risk assessments. This framework defines risks broadly, as a function of hazard, exposure and vulnerability:
Risk = Hazard ∗ Exposure ∗ V ulnerability (1)
This formulation is commonly used to estimate the impacts of climatic changes and has become the gold standard to assess populations’ and communities’ vulnerability to natural hazards and shocks [1, 2]. It is simple, flexible and generalizable, and enjoys wide consensus within the natural- science research community. An early application of this to the impact of conflict on humanitarian disasters is the INFORM Severity Index, in part based on research work by Eriksson et al. [3, 4]. The programme will build upon and expand this work to provide an integrated, cross-sectoral, detailed evaluation of communities’ vulnerability to adverse humanitarian impacts.
Risk is also formulated as the probability of war (the hazard) and the consequences when it occurs :
Risk = (probability of event) ∗ (severity of consequences) (2)
With hazard we mostly mean the probability of conflict of varying severity, although we will briefly also consider (in CC3) other hazards and treat conflicts as a source of vulnerability. We will refer to the consequence of conflict as observed as the impact.
Exposure refers to the inventory of elements in an area in which hazard events may occur and thus identifies the presence of people, livelihoods, infrastructure, economic, social, or cultural resources that could be adversely affected by the hazard . Exposure is a key dimension of risk: humanitarian disasters occur only when hazards affect where people live.
Vulnerability indicates the propensity or predisposition to be adversely affected– a lack of re- sources and capacity to cope, adapt and recover from shocks which enhance adverse effects on the exposed communities. Generally, vulnerability refers to the potential for loss; as the magnitude of losses changes over time and space, and among different groups, vulnerability equally varies . Vulnerabilities partly stem from social inequalities, which shape communities’ ability to respond and recover from shocks  and partly from place inequalities, including the level of urbanization, growth rates, and economic conditions .
Although often conflated, exposure and vulnerability are distinct. Exposure is a necessary, but not sufficient, condition for risk to materialize. Communities can be exposed but still avoid being vulnerable to hazards, at least partially, provided that they have means and tools to adapt and recover. For example, some can migrate out from the conflict area, others can not.
This risk framework enables us to provide a detailed assessment of humanitarian impacts of conflict in a broader sense than the one provided by only traditional formulations. For example, health status can be seen as a product of exposure to hazards, whereas vulnerability is a function of the financial and human resources and means available to address the risk-increasing conditions and the extent to which these resources are efficiently allocated .
We will link the estimate of conflict exposure to outcome-specific vulnerabilities. For instance, warfare itself exposes human populations through damages to power plants, water systems, and other infrastructure. Some socio-economic, gender, and age groups are likely to be disproportion- ately affected by these outcomes, as systemic discrimination increases their vulnerability to shocks . Other exposures come indirectly. For instance, population displacements expose both migrant populations and the residents of the locations they move into to infectious diseases puts social cohesion under pressure and stretches infrastructures to provide water and health services to the limits.
Complex systems: how impacts interact
For centuries, science has helped us understand the world around us by breaking systems into their components. Many important questions, however, can only be answered by looking at systems as units and observing the relationships across these units . ‘Complex Systems’ is a scientific approach to study how relationships between units give rise to the collective patterns of behaviors of a system . Complex systems are characterized by non-linearities, self-organization, and the ‘emergence’ of global properties and behaviors. These higher-order properties arise from the interactions among the system’s component, but cannot be understood when looking at each part in isolation .
According to this approach, social systems are complex adaptive systems, as they are open and able to adapt to their environment . Due to interlinkages between components and to their openness and exchanges with the external environment, complex systems can be more vulnerable to adverse outcomes than simpler ones . To gain a broad understanding of the impacts of armed conflict, we will adapt a complex systems approach, accounting for how six interlinked ‘systems’ interact with each other. These are public health, economics, water, social-psychological aspects, political institutions, and forced population movements. These effects of war are typically studied in isolation, but they clearly interact. To study the whole system in its complexity and understand the emergence of systemic patterns of behavior, the programme will be organized as a combination of ‘single-system’ work packages and a set of cross-cutting packages that bind these together.
The health system that is the focus of WP1, for instance, explores how individuals’ health responds to disease vectors and prevalence of diseases in their geographical proximity, but also to the provision of public health such as immunization programmes and maternal health care, nourishment, and access to water. As such, the health system critically depends on the economic system at the core of WP3 and WP4, as resources available for public health provision diminish due to destruction, diversion, dis-saving, and disruption . Likewise, health is related to the water system studied in WP5 [15, 16]. Access to clean water decreases early childhood mortality and waterborne infectious diseases [17–19].
We will also study indirect effects. Impacts of conflict on water provision, for instance, are detrimental for agricultural economics and fuel internal displacement (R1). Outside of combat zones, the lack of fuel for groundwater pumping, damaged water pipes, or dysfunctional waste- water treatment poses serious consequences for local populations, often forcing them to flee . The recent cholera outbreak in Yemen has been the worst such epidemic in modern history [21, 22] and further driven displacement. Armed conflict also diminishes vaccinations efforts and exacerbates the impact of Ebola [23, 24].
Armed conflict also affects psychological health and social cohesion, the topics of what we call the ‘social-psychological system’ (WP2). This system also interacts with the others. For instance, access to piped household water strengthens social integration and mental health . Trust and social cohesion are important to economic growth and to functioning political systems.
By studying the systems jointly, we will be better able to understand and anticipate when conse- quences of violence are particularly disastrous. For actors that seek to mitigate these consequences, an analysis of how the systems interact may suggest what actions are particularly effective.
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