complex, that wildfire eviscerating 10% to 14% of the world's giant sequoia population. brigham says this means in just the last two years, up to a fifth of mature sequoias, trees that have stood for at least 1,000 years, if not more, have been lost to wildfire. >> that's not sustainable. that is not getting wildfire and climate change resilient for us. >> reporter: it's a conflux of concerns these scientists never thought they would see. the threat made worse by another year of drought, leaving the sequoias dry and vulnerable. >> that means its water source has been there for over 2,000 years. that that water's not there means that the climate, the world around it, has changed. >> reporter: but lessons learned last year helped save some sequoia this year. >> before the castle fire, we had never seen losses of large trees like we had in that fire. 7,500 to 10,600 large sequoias lost in a single fire event, and that really changed what we