Mr Karrila, from Espoo in Finland, came out top in the 26th annual competition that tests 15- to 16-year-olds and their knowledge of forest biology, forestry and the forest industry and the environment in the country.
The final of the quiz saw 15 schoolchildren go head-to-head in a field exam, where they had to identify damage caused by snow, name a range of species and argue how to manage an area of forest.
Tomi Ellala and Maiji Vesterinen came second and third respectively in the competition, which is supported by UPM Forest, Stora Enso Forest, the Finnish Forest Association and a host of other firms.