. >> tom coleman is an entomolgist with the u.s. forest service. >> there's a lot of dead trees right here. >> yeah, this is a nice little active spot for bark beetles. >> bark beetles kill more trees than any other kind of insect or disease in north america. when you look across the landscape and see this patch work of dead trees. the mortality is quite dramatic. >> so this tree here is full of thousands of bark beetles, does that mean all the trees around here are now susceptible? >> right now from what i've seen it's just basically across the entire landscape. >> have you ever seen it this bad? >> not here in california. >> so just 10 minutes away we were looking at the devastation caused by pine beetles and now we can see the damage done by forest fires, there's a lot going on here. so even though the wildfire's actually gone through an area and caused major mortality, we'll still see bark beetles coming in afterwards. >> scientists studying our forests are concerned about the impacts from drought -- not just in california, but