According to the U.S. Drought Monitor, 39% of the U.S. land area is currently experiencing moderate to exceptional drought that is affecting more than 74 million people, particularly across the West and Northeast. Recently, NOAA’s Climate Prediction Center predicted that southern parts of the U.S. may experience expanded and intensifying drought during the winter months ahead, due to the La Nina climate pattern.
Rising temperatures increase the rate of evaporation, drying out soils as well as adding moisture to the atmosphere and changing precipitation patterns. This gives rise to an intensification of the water cycle which, simply put, is making wet places wetter and dry places drier. Drought is one of the costliest disasters in the U.S., causing an average of 94 deaths and an inflation-adjusted $6.2 billion in losses per year since 1980.
There are different ways to think about vulnerability to weather and climate events. A recent study considered drought vulnerability as being driven by three factors: exposure, sensitivity and adaptive capacity. The study defined:
- Exposure – the frequency of drought, the state’s population, and the freshwater ecosystems that could be affected
- Sensitivity – a state’s likelihood of being negatively impacted by drought, taking into account industries such as agriculture, water recreation and hydropower
- Adaptive capacity – a state’s preparedness for drought and ability to recover, looking at the state’s drought plan, irrigation infrastructure and economic strength
In this study, researchers found that states ranking highest in overall vulnerability often had less to do with how frequently drought occurs, and more with how prepared the state is for drought impacts. For instance, Oklahoma was ranked as the most vulnerable state due largely to its extensive cattle ranching and other agricultural enterprises, as well as limited possibilities for irrigation. Two other midwestern states, Iowa and South Dakota, made the top five most vulnerable list, in addition to Montana and Arizona.
A low vulnerability score does not mean a state is not (or will not) experience drought conditions. California, often one of the first states that comes to peoples’ minds when they think of drought, has one of the lowest vulnerability scores. This is due to California’s relatively strong economy and robust adaptation measures, which make it more resilient than other states with more limited adaptive capacity.
The Northeast was considered a less vulnerable region as a whole, with a few notable exceptions. High population densities and an abundance of protected freshwater ecosystems contributed to high exposure scores for New Jersey and New York. In addition to protected waters, Maine’s hydropower and water recreation industries make the state more susceptible to adverse economic impacts in the event of a drought.
By assessing these three categories, this study helps states identify what makes their state vulnerable to drought, to help inform addressing drought in the future.
You can find more information and resources on drought and climate change here:
Drought vulnerability index data for the contiguous United States was obtained from Engström, Jafarzadegan, and Moradkhani, 2020.