Page 11 - Green knowledge 2025

Photo: Arne Steffenrem
Old-growth forest mapped
New nationwide maps provide better knowledge of old-growth forest.
In February 2024, the Norwegian Environment
Agency was tasked with producing the first version of
a publicly available map of existing old-growth
forest, defined as forest that has not been clear-cut
since around 1940. The work resulted in three maps,
each representing a different approach to mapping
old-growth forest.
The first map follows the definition of old-growth
forest given in the mandate. It shows an overview of
forest established before 1940 that has not been
clear-cut since.
The second map shows forest areas established
before 1940 where no interventions or management
have been recorded since around 1965. The map
indicates the likelihood that the forest meets these
criteria.
The third map shows the degree of old-growth forest
characteristics across seven classes, from the least
old-growth-like to the most. The classification is
based on old-growth indicators described using a set
of variables from Nature in Norway 3.0: proportion
of dead wood, variation in dead wood, and forest
development.
The new old-growth forest maps were developed
using remote sensing data, i.e., satellite imagery and
airborne LiDAR, combined with machine learning
and computer modelling. The maps are raster-based
with a pixel size of 16 × 16 metres, making them
compatible with the SR16 Forest Resource Map.
According to the National Forest Inventory, approxi-
mately 2.5 per cent of Norway’s forest is highly old-
growth-like, while around 40 per cent has a low
degree of old-growth characteristics. In addition, the
inventory has increased plot density in protected
areas to better monitor development there.
Data from the National Forest Inventory have great
potential for mapping biodiversity, ecological condi-
tion or old-growth characteristics. This will also
enable projections of future forest development.
Purpose: Collaboration: New nationwide maps provide better knowledge of old-growth forest.
Norwegian University of Life Sciences, Norwegian Institute for Nature Research, Natural History
Museum, University of Oslo
Funding: Norwegian Environment Agency
Contact: Research Scientist Marius Hauglin, Division of Forest and Forest Resources.
Email: marius.hauglin@nibio.no | Phone: +47 994 59 839
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