reporter: the valea cernei national park in romania's southern carpathians.this is a nature preserve. cutting down trees here is strictly prohibited. but on hikes, biologist gabriel paun increasingly comes across logging sites that have left massive scars on the landscape. >> look at the way they've felled trees here. it looks like they must really hate this forest. this is a crime. it's a criminal offence. reporter: to stop it, paun founded the environmentalist organization "agent green". the biologist distrusts the country's environmental most forest rangers are corrupt, he says, and work hand-in-hand with the illegal loggers. that distrust comes to the fore when paun presents his findings to the park's local director. >> what you're telling me isn't true. when were you there? >> just now. i came straight here. >> it'll grow back. this is part of our regeneration program. >> what's going to grow there? it's been clear-cut! right in the middle of a national park! >> there's been no clear-cutting. i have to go now. reporter: not long ago, the environmentalist