Course:CONS200/2026WT2/The Use of Prescribed Burning in Sweden for Conservation and Biodiversity Outcomes

Introduction

A prescribed conservation burn (naturvårdsbränning) in Sweden. Controlled fire is applied to restore natural disturbance conditions in boreal forests and promote fire-dependent biodiversity.

Prescribed burning refers to the controlled application of fire by land managers to achieve specific ecological or conservation goals, including the restoration of fire-dependent habitats and the promotion of biodiversity. In Sweden, boreal forest — dominated by Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) — covers approximately 60% of the country's land area and represents one of the most ecologically fire-shaped landscapes in Europe. Within these forests, prescribed burning has become one of the most important tools for ecological restoration, used to recreate the natural disturbance conditions that maintained structural complexity and species diversity across the boreal landscape for thousands of years.

Historically, wildfires occurred regularly across Sweden's boreal forest, driven by lightning strikes and, from the mid-17th century onward, increasingly by human activities such as burning to improve cattle grazing and facilitate slash-and-burn agriculture. Dendrochronological reconstructions using fire-scar records from living and dead Scots pine trees have shown that, before industrial fire suppression began in the 19th century, coniferous forests in northern Sweden burned at a mean return interval of approximately 80 years. These recurrent fires performed a foundational ecological role: they opened the forest canopy, released nutrients into the soil, generated large volumes of sun-exposed deadwood, and created the structural heterogeneity — including fire scars, charred snags, and post-fire early-successional patches — that supported a distinctive and diverse assemblage of fire-adapted organisms. The result was a dynamic mosaic of stands at varying stages of post-fire succession, which formed the ecological template in which boreal biodiversity evolved.

The aftermath of a forest fire in Sisjön, Gothenburg, Sweden, illustrating the structural legacy that fire creates: open canopy, exposed deadwood, and early-successional habitat — conditions that prescribed burning aims to replicate in managed conservation burns.

However, from the second half of the 19th century onwards, the rapid expansion of industrial timber production provided powerful economic incentives to suppress and prevent fires across Sweden. The expansion of road networks, firefighting infrastructure, and systematic forest management effectively led to the virtual eradication of fire from the Swedish forest landscape. By the mid-20th century, fire had ceased to function as a meaningful ecological process across most of Sweden's managed boreal zone. Over time, the resulting absence of fire produced denser, more structurally homogeneous forests characterised by reduced deadwood volumes, fewer open sunny habitats, and declining populations of fire-dependent species — a phenomenon widely documented as a "fire deficit" in the ecological literature. Sweden is estimated to harbour at least 100 fire-dependent species, many of which are now classified as threatened or red-listed, a direct consequence of this prolonged fire suppression.

In response to this ecological decline, Swedish forest managers and conservation authorities began reintroducing fire as a deliberate management strategy from the 1990s onward, initially through conservation burns in nature reserves and national parks. Today, prescribed burning is institutionalised through the Forest Stewardship Council (FSC) certification standard, which requires Swedish forestry companies to burn an area equivalent to at least 5% of their harvested forest area over every five-year certification period, for biodiversity conservation purposes. Burns are administered both on clearcuts and on standing forest, and are executed by a combination of forestry companies and county administrative boards. The EU-funded Life Taiga project (2015–2020) further expanded this effort, involving 14 regional county boards and aiming to conduct 120 controlled fires in boreal nature reserves across Sweden with the explicit goal of restoring fire-associated biodiversity.

While these initiatives have substantially increased the scale of prescribed burning across Sweden, conservation outcomes remain variable and are not yet consistently meeting restoration targets. A key limitation is that prescribed burns are typically conducted earlier in the summer and under less extreme weather conditions than natural wildfires, resulting in lower fire intensity, reduced tree mortality, and smaller volumes of fire-generated deadwood compared to natural fires. Since the conservation value of burning tends to increase with fire intensity and pre-fire standing tree volume, these relatively mild managed burns frequently fall short of fully replicating the ecological effects of wildfires. Additional challenges — including regulatory restrictions, risk management concerns, the spatial mismatch between burn locations and the habitat requirements of fire-dependent species, and limited coordination between actors — continue to constrain the effectiveness of prescribed burning as a long-term conservation strategy.

This page examines the use of prescribed burning in Sweden in detail, exploring its historical evolution, the ecological principles underlying its application, the biodiversity outcomes documented in the scientific literature, and the ongoing challenges faced by practitioners and policymakers when scaling up and optimising this practice for long-term conservation.

Historical Context

Wildfire is important to the development of Sweden's Boreal Forest Ecosystems. Prior to the establishment of modern forest management practices, wildfires regularly burned across much of the landscape due to both lightning and human activities. These wildfires created a mosaic of forests at varying stages of development and also created many habitat types that depended on the periodic disturbance created by fire.

Historical research suggests that fires occurred relatively frequently in many Swedish boreal forests, with intervals often ranging from several decades to about a century, depending on climate and forest conditions. In fire-prone regions of Sweden, Scots pine trees are naturally suited to these environments due to several characteristics. These characteristics include a thick bark that provides an insulation layer from low and moderate-intensity fires and their ability to regenerate well in open and prepared areas after a fire has occurred. As a result, historically, forest ecosystems dominated by pine have formed in many of these fire-prone habitats of Sweden.

Melanophila acuminata, a pyrophilous jewel beetle, uses specialized infrared receptors to detect forest fires from afar. It arrives at burn sites within hours to lay eggs beneath the charred bark of freshly killed conifers. Prescribed burning in Sweden aims to support this fire-dependent species, whose populations have declined sharply due to decades of fire suppression.

However, forest management practices began to change significantly in the 19th and 20th centuries. With the industrialization of forestry, firefighting became a top priority to protect timber resources. Improvements in transportation systems, organized fire monitoring, and modern firefighting techniques made it possible to prevent or quickly extinguish many wildfires.

Although fire suppression reduced economic losses from wildfire, it also changed the ecological dynamics of Swedish forests. Over time, the absence of natural fires led to denser and more homogeneous forests with fewer open habitats and lower amounts of deadwood. These structural changes negatively affected many species that depend on fire-created habitats. Consequently, both ecologists and forest managers gradually recognized that fire represents not only a disturbance but also an essential ecological process for maintaining biodiversity in boreal forests. Which this historical shift in fire regimes helps explain why prescribed burning has become an important conservation tool in Sweden today, as it aims to restore some of the ecological functions once provided by natural wildfires.

Prescribed Burning

The history of prescribed burning in Sweden is a tale of dramatic transformation: from a natural ecosystem process to an adversary of the industrial state, and ultimately to a mandated tool for biodiversity conservation. The modern practice "came to fruition" through two distinct waves: an early 20th-century silvicultural movement led by Joel Wretlind, and a late 20th-century conservation movement driven by FSC certification.

The Era of Fire Suppression (Mid-19th Century)

Historically, Swedish boreal forests experienced frequent fire, creating a mosaic of age classes, open sun-lit habitats, and standing and fallen deadwood essential for biodiversity. As the timber industry expanded in the mid-1800s, however, fire came to be viewed primarily as an economic threat to commercial timber stocks. By the 1860s, the Swedish state had organized state forests with a systematic fire suppression infrastructure, and deliberate burning by settlers for cattle grazing gradually ceased under increasing legal enforcement.

The ecological consequences of this suppression were severe. Fire-scar records across a 608 km² study area in northern Sweden reveal that the number of fires per unit area peaked at 1.17 fires per 10,000 hectares per year during 1840–1860, then dropped sharply after 1870 as suppression took hold. Pyrophilous species — those ecologically adapted to fire-disturbed conditions — began disappearing from the landscape as the fire return interval grew far beyond anything their life histories could accommodate. Species such as the beetle Stephanopachys substriatus and the herb Geranium lanuginosum, which require burned substrate to reproduce, became increasingly rare.

The First Wave: Joel Wretlind and Silvicultural Burning (1920s–1950s)

The specific technique of prescribed burning in Sweden is most closely associated with Joel Efraim Wretlind (1888–1965), forest manager for the Malå district of Västerbotten County from 1920 to 1952. Sometimes called "the father of prescribed burning" in Sweden, Wretlind arrived in Malå to find forests left in poor regenerative condition following decades of high-grade logging that had removed the largest commercially valuable trees while leaving the stands structurally degraded.

Through empirical observation and systematic field experiments, Wretlind concluded that the thick moss and raw-humus layers covering the ground in mesic boreal stands were the primary barrier to Pinus sylvestris regeneration, and that fire was the most effective way to clear them and expose mineral soil. His method involved carefully prepared firebreaks, protection of seed trees, and controlled strip head-fire ignition against the wind — techniques that became the foundation of modern prescribed burning practice in Scandinavia.

Between 1921 and 1970, at least 11,208 hectares of Malå state-owned forest were burned through prescribed burning under Wretlind's program and that of his successors, representing 18.7% of the district's total forest area. During peak years, the burned area approached historical fire regime levels documented for the pre-suppression era. His methods were initially met with significant institutional resistance — colleagues accused him of recklessness, and his academic application for a lectureship was rejected — but by the late 1940s Malå had become a destination for foresters across Sweden seeking a solution to widespread regeneration failures in the northern interior.

Wretlind's influence spread across all of northern Sweden during the 1950s–1960s, when prescribed burning (Swedish: hyggesbränning) was applied at a national scale for regeneration purposes, with an average of approximately 35,000 hectares burned per year between 1952 and 1955, representing around 17% of the national regeneration area. From the second half of the 1960s onward, however, the method was largely displaced by mechanical soil preparation and planting of monoculture pine, which were cheaper and weather-independent, and prescribed burning declined sharply once again.

The Second Wave: The "Green Resurrection" (1990s–Present)

The modern reintroduction of prescribed burning for conservation purposes — rather than timber regeneration — emerged in the 1990s, driven by a fundamental shift in ecological understanding and by the introduction of market-based certification standards. Since the 1990s, conservation burns have been conducted within Swedish nature reserves, and the Forest Stewardship Council (FSC) certification — required to sell timber to many international markets — mandates that certified forestry companies apply prescribed burning to at least 5% of their clear-cut area on dry-to-mesic forestland over a five-year period, for biodiversity conservation purposes.

Unlike Wretlind's burns, which were designed to maximize pine regeneration, modern conservation burns are often deliberately intended to produce standing deadwood, open post-fire habitats, and the structural heterogeneity that fire-dependent species require. Forestry companies and county administrative boards are the two main executing parties, though they operate with largely separate registration and evaluation systems and limited coordination between them.

Despite these efforts, the scale of burning remains far below historical levels. Data collected across Sweden from 2011 to 2015 show that only 0.006% of Swedish forest burns per year on average, with forestry companies responsible for 86% of all prescribed fires and 58% of those occurring on clearcut sites rather than standing forest. By comparison, the historical fire rate prior to industrial suppression was approximately 0.8% per year — more than 130 times greater.

The main conservation goals of prescribed burning are to promote multilayered Scots pine (Pinus sylvestris) forests, increase deadwood volumes, create fire-scarred trees, and improve soil conditions for deciduous regeneration.

A significant driver of prescribed burning in Sweden is the Forest Stewardship Council (FSC) certification standard, which mandates that larger forest owners burn approximately 5% of their annual clear-cut area on dry-mesic forestland. This policy, often referred to as the "Green Resurrection," institutionalized prescribed fire as a standard tool of sustainable forest management and significantly increased the scale of burning across the country. Between 2011 and 2015, prescribed fires accounted for about 65% of all forest burns in Sweden, with wildfires making up the remaining 35%.

The technique aims to benefit fire-dependent (pyrophilous) and deadwood-dependent (saproxylic) species, many of which are now red-listed due to the long absence of fire from managed landscapes. Research indicates that prescribed burning generally suppresses bark beetle pest populations while supporting higher abundances of their natural predators, suggesting ecosystem-level benefits beyond direct habitat creation. However, conservation outcomes vary considerably between sites, with drier weather conditions and higher proportions of Norway spruce in the stand both linked to better results in terms of deadwood production and deciduous tree regeneration.

A key limitation of prescribed burning compared to natural wildfire is fire intensity. Prescribed burns are typically conducted under safer, lower-intensity conditions, resulting in lower tree mortality and less structural heterogeneity than wildfires produce. To maximize effectiveness, research suggests that burn planning should better align conservation objectives with site characteristics, stand composition, and seasonal weather conditions.

Implications for Reindeer Habitat and Sámi Stewardship

We understand that prescribed burning can increase biodiversity in certain tree species, as noted earlier. Still, there's much more to understand about the reasoning for the controlled burning of Sweden's forests. One other key idea involved in prescribed burning is an increase in habitat. By controlling the amount to burn down, we are able to introduce new species and wildlife into the area. Species that originally couldn't survive in the previous environment are now able to move into these areas and live within the vicinity.

Sweden has been trying to increase habitat through prescribed burning since the 1900s. Between the 1920s and 1970s, Sarah Cogos investigated this procedure by viewing how fire management affects the Sami reindeer herders in Sápmi. Around this time, although the forest owners and the indigenous Sami both used the land in Sápmi, it was the foresters who were able to make the fire management decisions, whether it be fire suppression or prescribed burning. Because of this, the Sami reindeer herders had to deal with the consequences that others made for them. The Sami found it unjust that they had no say on what to do for the last and what was best, not only for the people, but also the reindeer, as stated: "Sami reindeer herders, being deprived of land property rights, are subject to the decisions of forest managers and private forest owners, including fire management strategies." (Cogos, P.295, 2022). If the Sami were able to have at least a say or even control the levels of prescribed burning, they would be able to affect the habitat of reindeer as "The Sami consider the effects of burning in terms of fodder availability, opportunities for reindeer to graze the fodder, and any impact on the reindeer's movement patterns and thus herd management." (Cogos, P295, 2022). This method differs from traditional land stewardship in that prescribed burning is much more intense than in traditionally slower-paced environments. This can help add a big shock to the system and can even result in swift changes in the environment. By the end of the investigation, people found out that the Sami's reindeer herding was involved and considered during the planning process, but foresters failed to follow through with the important conditions and effects that would come with reindeer herding and prescribed burning.

Without Collaboration, both sides were unfortunately unable to reach a common goal or consensus. If they were able to work together, they would both be able to leave with what they wanted. The good news is that this was nearly 60 years ago, and Sweden has been pushing for multiple solutions to make the environment better for everyone. They have been pushing for things such as an increased usage of prescribed burning, fire suppression and community involvement in decision making through the FSC. After many years to develop, Sweden now works with the community to help with prescribed burning to increase the biodiversity of species such as the saproxylic beetles and wood decay fungi in boreal forests.

Conclusion

Prescribed burning in Sweden represents a significant reorientation in boreal forest management, reflecting a broader scientific consensus that fire is an integral ecological process rather than solely a destructive force. Decades of fire suppression produced a measurable fire deficit across Scandinavian boreal landscapes, diminishing habitat heterogeneity, reducing deadwood accumulation, and placing numerous pyrophilous species under conservation pressure. Prescribed burning has since been adopted as the primary practical instrument for partially restoring the structural and biological conditions that natural wildfire regimes historically maintained.

A low-intensity surface fire moves through young Scots pine and Norway spruce trees in a Swedish boreal forest. This ground-level fire consumes surface vegetation while leaving taller trees standing, a characteristic of prescribed burns used for ecological restoration. Smoke billows into a partly cloudy sky as the flame front progresses slowly.

Nevertheless, prescribed burning operates within recognized limitations. Controlled burns typically generate less spatial heterogeneity than unmanaged wildfires, and ecological outcomes vary considerably depending on site conditions, fuel loads, and burn intensity. The practice also intersects with the land rights and seasonal herding patterns of the Sami people, necessitating consultation frameworks that have not always been consistently applied. These factors have prompted calls within the scientific and policy communities for more ecologically targeted burn planning and more substantive engagement with Indigenous stakeholders.

Within Sweden's broader nature conservation framework, prescribed burning has become one of the most consequential management tools available for boreal biodiversity. Its long-term effectiveness, however, is contingent on the rigor of ecological planning, the adequacy of institutional resources, and the degree to which land management decisions are developed in genuine partnership with affected communities.

References

This conservation resource was created by Course:CONS200.