“Atmospheric Thirst”, Drought, and the HCP

Local ecologist and wildfire expert George Wuerthner alerted me to a new report publish by the American Geophysical Union with the unwieldy title “Projected Changes in Reference Evapotranspiration in California and Nevada: Implications for Drought and Wildland Fire Danger“. While Central Oregon is not specifically covered, it is obvious from the report that it applies to us as well. The bottom line is that global warming is going to increase and strengthen the extended state of drought we have been experiencing as well as increase and strengthen local wildfire danger. George asks how will this impact the HCP and our management of local rivers? What breaks when there is not enough water to meet all the defined needs?

Here’s the “plain language” executive summary:

Since the start of the 21st century, California and Nevada have observed extreme wildland fires and droughts that have caused devastating impacts to ecosystems and society. A common feature of these events has been very high atmospheric evaporative demand—the “thirst” of the atmosphere—which has largely been driven by increased air temperatures caused by anthropogenic climate change. This study examines projected changes in evaporative demand, which of the input variables are causing those changes and how the frequency of extreme wildfire potential and multiyear droughts will change. Evaporative demand is found to increase during all seasons, and increased temperatures drive most of that change. The likelihood of extreme wildfire potential based on 2‐week periods of elevated evaporative demand during summer and autumn increases substantially. A climatic water balance based on precipitation and evaporative demand indicates extreme 3‐year droughts that hold potential to deplete regional‐scale water supply also become much more likely. Future adaptation planning efforts for wildfire management agencies, forest management, and water resource managers should account for a greater likelihood of more extreme events.