National Forest Inventory

The National Forest Inventory (abbreviated to WISL in Polish) is a monitoring system which provides information on structure, resources (timber volume, increment, and use), and health status of forests.

Our forest management specialists go into the field regularly, measuring and surveying thousands of forest plots in order to assess their condition. We use this knowledge to indicate the direction of change of this condition on a large-area scale. These inventories are designed to provide reliable, up-to-date information about the forest, in particular on species and age structure of stands, their health, and the occurrence of forest damage.

Measurements and observations of the National Forest Inventory have been carried out by the Bureau for Forest Management and Geodesy continuously since 2005. Every year, around 70 teams go into the field to collect data on nearly 7,000 sample plots, distributed in forests across the whole country in a regular network of 4 by 4 km. In each successive five-year inventory cycle of WISL, the number of sample plots increases (from about 29,000 in the first to over 33,000 in the last inventory cycle) as a result of both still increasing Poland's forest cover and the inclusion in WISL the inventory of forest areas that are not taken into account in any other national or international statistics.


The data coming from WISL is controlled at both the fieldwork and laboratory stages. Software used in the fieldwork has control mechanisms to detect potential errors, allowing for ongoing correction of data input on the spot. The quality of work is verified by the Bureau's internal auditors as well as external audits of the State Forests and the Forest Research Institute. The Institute also provides scientific support for WISL.

By carrying out inventories in successive cycles, an extensive base of reliable data on forests of all forms of ownership in Poland has been collected. These data and generated on its basis information about forests are used to shape the state's forest policy, as research material for science, as a source of data for Polish state statistics and international statistics, as well as in forest management planning. Thorough reports and data compilations are made available to the public on the National Forest Inventory website and in the Forest Data Bank.