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.