Disaster Trees

The study guide for the course included an activity called the "disaster tree", in which we were instructed to classify the various disasters that impact humans into four categories: "natural", "man-made", "hybrid" and "intentional". The tree, like our knowledge about disaster, should evolve and change throughout the semester and as such, I will add a number of different versions to this post over time. The following is my first attempt at classifying all of the disasters that I can think of off of the top of my head.

My first attempt was not bad, however reading through the course material I have noticed that I was missing several disasters. Among them were landslides and avalanches, nuclear catastrophes, famines and epidemics, all of which I knew of but had not come to mind when I thought of disasters. I also had not included limnic eruptions, a disaster that I learned about by watching the SBS series "Countdown to Catastrophe". Limnic eruptions occur when lakes near volcanoes fill with carbon dioxide which then erupts and asphyxiates the living beings in the surrounding area.

After reading “Natural Disasters” by Redmond (2005), I also began to consider what constitutes natural and man-made disasters very differently, which led me to propose an alternate disaster tree including more of the events that I have been learning about. In the journal article, Redmond states that all disasters are essentially human made based on where and how people choose or are obligated to live. As a result, I removed the vast majority of the disasters that I had initially listed as natural and reclassified them under the “Hybrid” branch instead. The only two that I left in the “Natural” column were asteroids and tornadoes because they can occur anywhere and severely impact populations regardless of how they live. While it is widely accepted that anthropogenic (human made) climate change is increasing the frequency and severity of storms and other natural disasters, its impact (if any) on tornadoes is still unknown. However, I did ultimately add tornadoes to the hybrid branch as well, due to the fact that some populations of people have chosen to reside in areas that are frequently hit by tornadoes (i.e. “tornado alley” in the United States) despite the well-known risks associated with living there.

While I do understand Redmond’s point of view, I struggle with the idea that all natural disasters are fundamentally human made. After all, as a species humans do need to live somewhere and there is nowhere on Earth that is completely immune to all forms of natural disasters. Therefore, human beings would be responsible for all natural disasters that affect them simply by being alive and in my opinion that is not enough of a reason to deem a species culpable. It would be the equivalent of saying that the damage to animal populations caused by a lightning-generated forest fire is fundamentally the fault of the animals for living in the area. There are simply some consequences of disasters that cannot be entirely avoided or prevented.

However, I do recognise that human beings are contributing to climate change and an increase in the severity and frequency of many natural disasters (i.e. storms, earthquakes, etc), thereby making some of them and the aspects of their occurrences both natural and man-made. But, since some number of natural disasters would occur with or without human contributions because of the Earth’s systems, it is my belief that the disasters that I had re-classified as hybrids for the second version of my disaster tree should actually fall under both the natural and hybrid branches. I have therefore added the anthropogenically-driven increase in the frequency and severity of natural disasters under the hybrid branch instead of re-naming them all as that is the aspect of them that I consider to be man-made. I have also added some more disasters that I had not previously included such as technological accidents, transportation accidents, The following is the final version of my disaster tree that reflects my own views of how disasters should be classified.

Disasters can also be classified under different characteristics. The following tree classifies natural disasters based on where they occur: "above the Earth's surface" or "under the Earth's surface".

I decided that I would position a disaster under the heading of "below Earth's surface" if the process began under the Earth's crust, even if the ultimate impact with humans occurred on the Earth's surface. For example, a tsunami is considered a disaster when it makes landfall and destroys life and man-made structures by flooding areas. However, tsunamis are typically caused by earthquakes in the ocean floor and therefore the process begins under the Earth's surface. This is how I decided that I would proceed with completing my tree in this case, but I am sure it is not the only way that classification could take place. I have found that classifying disaster can in fact be quite subjective depending on the factors and perspectives that are being considered.

Disasters can also be classified based on the nature of the systems through which they occur in the environment. The following tree categorises the disasters based on whether they are "meteorological/hydrological" or "biological" disasters.

There are surely other ways to classify disasters, perhaps by their impacts on humans, the type of damage that they cause, or maybe even where they tend to occur. However, these trees would likely be more complicated and have a great deal more crossover between categories as several disasters have similar impacts on human populations. For example, crush injuries, trauma and hypothermia can occur in earthquakes, storms, mudslides and tsunamis alike. There are also many areas on Earth that suffer from a wide range of disasters because of their location and/or topography, etc. Examples include areas with both active volcanoes and lakes that can act as the site of limnic eruptions.

I will continue to consider the various ways in which disasters can be classified throughout the remainder of this course and how these classifications may or may not be subjective.

Eryn