Fig. 2

GFC harvested area estimate based on NFI plots with and without correction for an increase in GFC’s detection ability after 2015. The two top figures provide the uncorrected timeseries of GFC harvested area for A Finland and B Sweden along with their field-observed management outcomes (final fellings, other harvest, thinnings, no loss recorded in the field = commission error). The area with final fellings is relatively stable while the area with detected thinnings increases considerably after 2015. The two bottom figures provide the timeseries of GFC harvested area corrected for GFC’s increased detection ability after 2015 for C Finland and D Sweden. For the period 2016–2018, the area is estimated assuming the correct detection proportion would have stayed the same as before. Based on these corrected area estimates, there is no abrupt increase in the harvested area after 2015. See Tables 1 and 2 in the Appendix for standard errors of estimates