State of forests and scarcity of timber were largely discussed in Finland already in the 19th century. At the second half of the century there were several attempts to roughly assess the condition of forests. Even small scale surveys were conducted. In 1913 the first Finnish statistical sampling based inventory of forest resources was conducted in two municipalities, Sahalahti and Kuhmalahti. It took eight more years before the methodology and necessary budget funds for the whole country survey were available. The first national forest inventory (NFI) was started in 1921. The field work was completed in the whole country by 1924 and the preliminary results were published the very same year.
Globally, Norway was the first country to start NFI. Sweden started NFI in 1923. Finland was the first country to complete the survey. This was noticed internationally – even the president of United States of America, President Calvin Coolidge, invited professor Yrjö Ilvessalo for a visit to learn how such a nation-wide survey can be successfully implemented.
The first NFI was designed to estimate the amount of growing stock, increment and condition of forests. Funding was secured by a committee preparing new tax system on forest properties. From today’s perspective, the information collected in the forests can be regarded quite narrow. Yet, the value of the NFI was immediately recognized and ever since NFI’s have been repeated with a cycle of 10 years, and with a cycle of 5 years since 2004. The ongoing NFI cycle is 13th.
Planning of national forest policies has been the most important motivation for funding NFI’s. The collected information has been used to prepare forest sector Master Plans with an aim to increase production of timber. In recent decades, these Master Plans or forest strategies have recognized the need for sustainable development, considering economic, ecological, and social aspects, and in recent years increasingly the need for mitigating climate change. These aspects are reflected in the information content and design of the current NFI. In 1980’s assessment of forest damage was introduced in the NFI, in 1990’s measuring biodiversity elements became part of NFI, and since the beginning of this millennium the needs of green house gas inventory have changed the inventory design from a regional survey to a continuously rolling inventory. For each sampled forest stand, more than 100 variables are today recorded to describe the forests in a multi-dimensional way.
Even though the first NFI was designed for the information needs of those days, it is still possible to derive interesting time series all the way from 1920’s to 2020’s. These time series reveal some surprising facts on the influence of changes in land use and forest management. The increase of growing stock is well known, but e.g. the increase in the amount of deciduous trees, large aspens and dead trees, may be surprising for most of us.
Measurements and observations in the field have always been in the core of Finnish NFI. Today we can measure trees with airborne laser scanning. Full cover of satellite images can be acquired for the whole Europe several times a year. For these reasons the need for laborous field work is some times questioned. However, it is obvious that a multi-resource NFI can not solely base on parameters that laser scanning can produce – we would not get proper information on sites, damage, dead wood and many other important elements in sustainable forest management. And the research article published in Nature in summer 2020 is a warning example how biased data we might produce if we would rely on satellite images without ground truthing, field measurements.
The first Finnish NFI was designed according to the very national information need. Today, the economies are global. International commitments and processes have influence on our national forestry and environmental policies. The EU LULUCF regulation, fresh biodiversity strategy and forest strategy under preparation are examples of EU level decisions that have effect on forestry in Finland. It is very important that the also the international strategies base on solid data on forests. The EU Member States need to find solutions to fully utilize the European NFI’s also at international processes.