Perturbations and shocks are common in food systems and involve both the “natural system” components and the “human system” components in these systems. Throughout modules 11.1 and 11.2, we will use the word shocks and perturbations fairly interchangeably to refer to these negative events that challenge food systems and their proper function, although the word "shock" denotes a perturbation that is more sudden and potentially disastrous. Perturbations and shocks in “natural” components include dramatic changes in climate factors such as rainfall, as well as changes brought on by biological components such as disease and pest outbreaks that affect plants and livestock. Similarly, perturbations can occur within the “human system” components of a system. For instance, food prices are rarely entirely constant and farmers and consumers are said to face "price shocks" in the purchasing of food.
Figure 11.1.1.: A photo of an Andean agroecosystem during the long dry season shows how water limits food production in some parts of the Andes. This system is thus very vulnerable to drought shocks, and its vulnerability is compounded by shallow, eroded soils that result from cultivating sloped land. These soils store less water than under their original vegetation cover and are thus more vulnerable. Credit: Steven Vanek
Figure 11.1.2.: This photo of dramatic flooding in Wisconsin, United States shows conditions of near certain crop failure or damage to pastures for these fields, which is a strong negative shock to local food production and farmer livelihoods. Farmers may, however, be somewhat buffered from economic hardship if they have crop insurance, and food security for local inhabitants may be buffered by movement and sales of food from elsewhere in the regional and global food system. Credit: United States Federal Emergency Management Agency, used with permission through a Wikimedia Commons creative commons license.
Extreme conditions can result in major perturbations and shocks in agri-food systems. Major climate variation, such as severe or prolonged drought, is a common example with regard to major changes emanating from the natural system (see figure 11.1.1). Gary Paul Nabhan, the author of the required reading in this module, uses the example of the extreme "Dust Bowl" drought in the United States in the 1930s. Since it is already a region that receives little rainfall, the agri-food systems in the U.S. Southwest were considerably threatened by this drought. Extreme conditions endangering food-growing and availability can also arise in human systems. Examples include political and military instability as well as market failures and volatility (such as the sharp increase in prices).
The human-environment dynamics of major perturbations and shocks in agri-food systems are shown in figure 11.1.3. This figure uses the already familiar approach of Coupled Natural-Human Systems (CNHS) introduced in Module 1 and applied in module 10 and throughout the course. Here we apply it to interactions of the natural and human systems that result in reduced production and accessibility of food. The human response to perturbations and shocks can be understood by applying the CNHS framework to agri-food systems. Within this diagram, we also want to emphasize that because of the coupling and interactions within and among these systems, the human and natural systems are never just passive recipients of a shock. Both subsystems have mechanisms for responding that can either ameliorate or worsen the "crisis" effects of perturbation. These system properties and responses to shocks are considered through the concepts of resilience, adaptive capacity, and vulnerability (RACV), defined on the next page. In the next module (11.2) we will use the RACV and human-natural systems framework to understand shocks and system responses that result in famine and severe malnutrition.
Figure 11.1.3.: The framework of Coupled Natural-Human Systems (CNHS) applied to Perturbations and Shocks in Agri-Food Systems. For both the human and natural systems, the characteristics and internal interactions of each will determine properties of resilience versus vulnerability, which influences what the final effect of a shock or perturbation will be. The internal interaction arrow of the human System is given a larger size, at center left of the image, to describe human-generated shocks such as conflict or economic crises (as well as their human mitigating factors in the form of preparedness or food aid, e.g.) can have in improving or worsening the impacts of shocks. Natural to human coupling is conceived of both as drivers and feedbacks because shocks that may seem to originate purely in the natural system, such as droughts and flooding, are increasingly understood to be feedbacks or responses to the damaging effects of human systems on natural systems such as soil erosion or climate change. Credit: Karl Zimmerer, adapted from the National Science Foundation.