Geographic Perspectives on Sustainability and Human-Environment Systems

Natural Hazards Across Scale


We study natural hazards because they are interesting and important, but also because we hope to reduce the damages caused by extreme natural events. Damage and losses from natural hazards is a major obstacle to sustainable development. In some sense, a community that can buffer the impacts of natural hazards is sustainable. Human populations always face natural hazards. When the impacts of an extreme event overpower a population’s abilities to cope (i.e., its resilience), there can be many significant losses, including loss of life, property, infrastructure (buildings, roads, etc.), and business. Sometimes these losses are so severe as to exceed the human system’s resilience and send it into a completely different state. For example, after Hurricane Katrina, many people moved out of New Orleans, never to return.

The natural hazards that we’ve discussed in this module have been mostly at local or regional scales. For example, the 2010 Haiti earthquake caused destruction mainly within one region of Haiti, which is a small country, with about the same land area as Maryland. The response to the earthquake was global, but the disaster itself was not. The 2004 Indian Ocean tsunami caused destruction over a broader region, including parts of over ten countries. But neither these disasters nor any of the others discussed in the module were global in scale. Why, then, are natural hazards studied in a unit on global environmental change?

Perhaps the most important reason to study natural hazards in the context of global environmental change is to develop an appreciation for the subtle and specific ways in which humans prepare for and respond to environmental change in general. Natural hazards involve some of the most dramatic environmental changes at any scale and thus offer us important case studies for human-environment interaction. As we have seen throughout this module, extreme events challenge humanity to respond to environmental change, often by taking measures (such as medical triage) that we are usually uncomfortable doing. In many cases, if we do not try to respond, then people die, and often in large numbers. Such is the same with environmental change in general, including with global environmental change. As the environment changes, for any reason and at any spatial or temporal scale, we face the task of responding. The scenarios may not be as dramatic as the extreme events discussed in this module, but they are every bit as threatening.

Another important reason to study natural hazards in the context of global environmental change is that some natural hazards actually are of global scale. One is the hazard of objects from outer space: asteroids and comets. The largest of these can cause massive global destruction. Indeed, an asteroid impact is believed to have caused a global extinction event about 65 million years ago. The risk is sufficient that NASA maintains an active impact hazard monitoring program. Another global-scale hazard is the supervolcano: a massive volcanic eruption thousands of times larger than typical eruptions. Such an eruption would darken the skies for years, threatening the survival of many species, including humans. Fortunately, large asteroid and comet impacts and supervolcano eruptions are very rare and thus unlikely to happen anytime soon. But they could happen. Given the stakes involved, they may be worth at least some of our attention.

Finally, for any discussion of environmental change, it is important to remember the scales at which we as humans experience the environment. No matter how broad-scale an extreme event may be, we only experience it within our own portion of the world: our field of vision, our range of hearing, our places that we exist in. For people in Indonesia that were hit by the 2004 Indian Ocean tsunami, on some level it did not matter that the tsunami also hit India, Somalia, and other far-off places. Their experience of the tsunami was immediate and local, as were the experiences of people in India, Somalia, and the other affected countries.

As we turn our attention to more global-scale processes, in particular, global climate change, it is important to remember that we experience these processes at the local scales of our lives. This holds for both the ways in which we help cause these global processes and the ways in which we are impacted by them. For this reason, we should keep in mind that global change is commonly experienced and addressed at local scales. Indeed, it is for this reason that the Association of American Geographers (AAG) lead a team of leading geography researchers to write a book Global Change and Local Places. The ideas behind this book are central to the final sets of modules and further illustrate the value of studying natural hazards in the context of global environmental change.

With that in mind, we will turn to one of the biggest examples of global environmental change - climate change - in our next module.