Regional tree die-​​off events gen­er­ate large quan­ti­ties of stand­ing dead wood, rais­ing con­cern over

cat­a­strophic wild­fire and other haz­ards. Gov­ern­men­tal responses to tree die-​​off have often focused on

incen­tiviz­ing bio­mass energy pro­duc­tion that uti­lizes stand­ing dead trees removed for safety concerns.

How­ever, the full dis­tri­b­u­tion of poten­tial woody bioen­ergy feed­stock after tree die-​​off has not been

eval­u­ated due to the com­plex­i­ties of sur­vey­ing and pre­cisely mea­sur­ing large forested areas. In this

paper, we present a novel method for esti­mat­ing stand­ing dead bio­mass at a fine spa­tial resolution

that com­bines aer­ial sur­vey data with for­est struc­ture maps. Using this method, we quan­tify biomass

gen­er­ated by the unprece­dented tree die-​​off that occurred in Cal­i­for­nia fol­low­ing a 4-​​year drought and

wide­spread pest out­breaks. The results are used to esti­mate fea­si­bly recov­er­able feed­stock for energy

pro­duc­tion. We find that approx­i­mately 95.1 mil­lion bone-​​dry tons (BDT) of dead bio­mass resulted from

2012–2017 mor­tal­ity, with a lower bound of 26.2 mil­lion BDT. In other words, of the above­ground live

tree bio­mass in 2012, ~1.3–4.8% died by 2017. Of the stand­ing dead bio­mass, 29% meets minimum

con­straints for poten­tial cost-​​effective bioen­ergy feed­stock. This pro­por­tion drops to as low as 15%

in the most affected areas due to ter­rain slope, wilder­ness sta­tus, and other fac­tors, high­light­ing the

need to com­ple­ment dis­posal via bio­mass energy with other strate­gies to mit­i­gate the risks of the tree

mor­tal­ity cri­sis, which is likely to only become more severe over time due to cli­mate change.