The Southwestern United States Face Unprecedented “Megadrought”


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By Grace Pooley

The western United States is no stranger to environmental woes such as seasonal wildfires and cyclical droughts. A new threat is on the horizon, however, one that is exacerbated by anthropogenic climate change—a reality that can no longer be denied. The megadrought—newly realized, not necessarily new—has descended upon the western U.S. over the past two decades. There has not been a megadrought in recent history; in fact, the only event even close to a megadrought in American recollection would be the Dust Bowl which lasted through the 1930s, a crisis that spanned just a decade instead of the current 20-year drought. 

According to the California Department of Food and Agriculture, California produces 13% of the United States’ food and the Southwest is home to a significant portion of grazing land in America— for context, 60% of Nevada is used for livestock grazing. The implications a drought this severe would have on food production is a significant concern. In the current global situation with the coronavirus, it is not unreasonable to link fear of food availability and resilience to sickness to the greater underlying threat of climate change. The Dust Bowl not only caused massive migrations of U.S. populations out of the affected states, but also tremendous economic hardship, food shortages, and irreparable land degradation. The worst megadrought in available history ravaged the southwest United States, known then as “New Spain” in the 16th century, likely aggravating the Spanish-brought fevers the indigenous population was already suffering from.

The current megadrought began in the early 2000s and has already surpassed the severity of the most recent droughts of the 1930s and 50s. Scientists are confidently linking the current drought to anthropogenic actions that have exacerbated climate change. A recent study published in Science magazine laid out this argument using sophisticated models based on variability in the moisture content of tree-ring records. The moisture content preserved in the tree-rings directly corresponds to the moisture content in that era’s soil. If there is a significant lack of moisture in these tree rings, the assumption can be made that there were drought conditions, such as lack of precipitation and subsequent excessive dryness. Their analysis of tree rings span 1,200 years and reveals that this current drought is the second-worst in recorded history. 

The lead author on the study, Dr. Park Williams with the Lamont-Doherty Earth Observatory at Columbia University, spoke with The New York Times, saying “We know that this drought has been encouraged by the global warming process, […] what appears to be a pretty strong long-term drying trend.” 

Dr. Williams and his collaborators on the study have corroborated that the greenhouse gas effect of our excessive emissions has contributed significantly—up to 50%—to this new drought. This evidence confirms that the megadrought is intensified by human actions. Arguably the scariest aspect of this new reality for the Southwest is that every human contribution so far has made it worse. Until the reality of climate change is faced head-on by actionable policies, this megadrought stands to be even more disruptive than the Dust Bowl was to Americans of the 1930s.

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