This study describes the impact of a wildfire caused by a tourist at Torres del Paine Biosphere Reserve in 2005, which destroyed approximately 2,000 ha of forests. Changes on biodiversity attributes of Nothofagus pumilio stands including structure, floristic composition and regeneration, are shown. We compared three plot groups having similar site and structure: Cordón Masle burned plots (CMBP); Cordón Masle unburned plots (CMUP), adjacent to the first ones; and Cerro Paine unburned plots (CPUP), outside the fire perimeter. Data was analyzed using univariate (Mann-Whitney) and multivariate (MRPP and ISA) non-parametric analysis. In CMBP, the fire reduced in average 91.7 % of the tree density and 70.9 % of the basal area. In the unburned plots the average of seedling was 23,625 and 22,750 ha^-1 in CPUP and CMUP respectively, whereas in burned ones it was only 1,125 ha^-1 in CMBP. Canopy layer collapsed and species richness and cover on ground increased significantly in burned plots. The average of exotics increased from 1.5 and 0.6 in CPUP and CMUP respectively to 11.9 in CMBP. Tree mortality, lower regeneration, biological invasion and broken canopy-ground balance in burned stands, are altering the successional pathways of forests, making difficult the forest regeneration and restoration efforts. Based on this information, we propose managers to encourage efforts in fire prevention and to incorporate a database on biodiversity indicators for management plans, in order to know more about the ecological integrity of ecosystems and the impacts provoked by recreation.