Increment and drain of growing stock 

Updated: 1.12.2017 - Next update: 2.10.2018

Timber reserves increasing each year

Finland’s timber reserves have increased every year for the past 40 years, and measurements in 2009 to 2013 indicate that reserves totalled 2,356 million cubic metres. The annual average increment of the current growing stock is 105.5 million cubic metres (representing a growth rate of 4.5%), and the drain in the period in question averaged 72 million cubic metres (a drain rate of 3.0%). These are overall figures that also include forests in nature conservation areas.

For decades, Finland’s growing stock increment stayed at approximately 55 million cubic metres, but in the 1970s it began to rise rapidly. There have been many reasons for this. One of the key factors is that the age structure of Finland’s forests has changed as the growing stock has become younger due to widespread forest regeneration. Furthermore, extensive peatland drainage affecting tree stands was carried out in the 1960s and 1970s, significantly increasing the area of productive forest land and its potential yield. The greater the growing stock, the greater the annual increment. The main trend in the drain of Finland’s growing stock has also been upwards. The forest industry has cut its production capacity in recent years, but at the same time, the use of energy wood in heating and power plants has increased. In recent years, the use of forest chippings has made a downturn, however.

Natural Resources Institute Finland

Description of indicator

The difference between the increment and the drain of the growing stock (a kind of simplified forest balance sheet) reveals whether or not the reserves of stemwood are increasing, decreasing or remaining unchanged. Timber volumes are expressed as solid cubic metres with bark.

The estimates of the growing stock increment are based on the comprehensive inventories of forest reserves made by the Finnish Forest Research Institute (1.1.2015 Natural Resources Institute Finland) since the 1920s. The growth in diameter and height of sample trees is measured over the preceding five years. In 2005-2008, the inventory of Finnish forests was conducted for the tenth time. For the eleventh inventory the results were calculated on the basis of 2009-2013 measurement years.

The estimates of the growing stock drain are based on comprehensive statistics; up to 1984 these were on timber use, and have since been on fellings and timber use. The drain is calculated by taking the timber volume for use and adding to it an estimate of the stemwood parts left in the forest from fellings and an estimate of the naturally expired trees.