Widespread Unquantified Conversion of Old Boreal Forests to Plantations

Across the boreal biome, clear-cutting of old, previously non clear-cut forests with high naturalness followed by tree planting or seeding is a major land use change. However, how much previously uncut forest has been converted to plantations remains unquantified. We combine Swedish national databases on clear-cuts and forest inventories to show that at least 19% of all clear-cuts since 2003 have occurred in old forests that were most likely not previously cut and planted or seeded. Old forests have been cut and lost at a steady rate of similar to 1.4% per year for the same period, and at this rate they will disappear by the 2070s. There is further evidence that this type of unreported forest conversion is occurring across much of the world's boreal forest. Plain Language Summary Natural ecosystems that have seen limited direct human impact are threatened by land use change. Land use in boreal regions is dominated by forestry but the rate at which older boreal forests with high naturalness are converted to planted and seeded forest for wood harvesting remains unquantified. We used a set of uniquely detailed databases and maps to estimate the share of old and previously uncut forests in annual harvests and at which rate these forests are being lost in Sweden. The results indicate that about a fifth of cut forest area since 2003 was cuts of previously uncut old forest. If the present trajectory continues, the remaining unprotected old and previously uncut forests will be converted to planted and seeded managed forests within a couple of decades. Given the slow development and distinct structural and ecological characteristics of these old forests, this loss may define the landscape for centuries.