Danish forestry in numbers

Approximately 11% of Denmark is forested. Originally focus was mainly on the potential of conifers, but in recent years focus has changed towards indigenous, deciduous tree species as offering greater long-term production and nature potential. Unlike its Scandinavian neighbours, Denmark is not a country in which forestry plays an important role in the national economy. The ambition is to have about 25% of Denmark’s area forested by the end of the 21st century. A considerable increase in the forest area is therefore to be achieved (1).

Vulnerabilities in Denmark

Higher temperatures, changed precipitation and increased storm risks will have negative consequences for a number of tree species and forest types found in Denmark. Some of the non-native conifer species will be especially vulnerable. Climate change can therefore mean unstable forests and forest death. All things being equal, this will cause loss of production and loss of the natural, landscape and recreational value of forests (2).

Droughts and forest fires

A majority of existing tree species that thrive well today are expected to persist in Denmark. Norway spruce, however, may be the exception. Norway spruce occurs naturally in regions with cold winters, and the species has already shown signs of poorer health in periods with warmer winters and much precipitation. Summers characterised by drought may have a potentially larger effect on Norway spruce, because its roots do not reach as far into the ground as other species. Norway spruce makes up approx. 28% of the area covered by vegetation, and – often being grown in monoculture – there is also a large risk of forest fires, even if today this is not a major problem (2,32).

Pests and diseases

Beside its effects on the growth of trees, regeneration dynamics, and stability, a changed climate may also pave the way for introduction of new pests or for propagation of existing known pests, which, possibly in combination with weakened vegetation, may cause problems relating to forest health and stability (2,32).

Storms

With intervals of 15 to 20 years Denmark experiences devastating storms, which cause heavy damage to stands with heights above 15 to 18 m. During the last 40 years, in 3 storms (1967, 1981 and 1999) a total of 10 million m3 were blown down, which corresponds to an average wind throw of approximately 10% of the annual cut. Since storm at present is a very important damaging factor in Danish forestry, smaller changes in storm patterns might significantly affect forest stability (3).

The most vulnerable region is the western part of Jutland, due to the combination of sandy soils with a low water holding capacity, frequent sea spray and wind exposure, and the predominant use of the basically unadapted Picea abies in monoculture. These systems have a very low resistance and resilience, thus being very susceptible to environmental perturbations (3).

Under the assumption that the wind climate will not change, the risk of windstorms for forestry between now and 2100 will increase considerably in Denmark, due to higher exposure and higher vulnerability (33).

Vulnerabilities - Overview

The increased vulnerability of forests (and people) with respect to climate change refers to several impacts (24,30):

• Forest cover: conversion of forests to non-woody energy plantations; accelerated deforestation and forest degradation; increased use of wood for domestic energy.
• Biodiversity: alteration of plant and animal distributions; loss of biodiversity; habitat invasions by non-native species; alteration of pollination systems; changes in plant dispersal and regeneration.
• Productivity: changes in forest growth and ecosystem biomass; changes in species/site relations; changes in ecosystem nitrogen dynamics.
• Health: increased mortality due to climate stresses; decreased health and vitality of forest ecosystems due to the cumulative impacts of multiple stressors; deteriorating health of forest-dependent peoples.
• Soils and water: changes in the seasonality and intensity of precipitation, altering the flow regimes of streams; changes in the salinity of coastal forest ecosystems; increased probability of severe droughts; increased terrain instability and soil erosion due to increased precipitation and melting of permafrost; more/earlier snow melt resulting in changes in the timing of peak flow and volume in streams. The capacity of the forest ecosystem to purify water is an important service, obviating the cost of expensive filtration plants.
• Carbon cycles: alteration of forest sinks and increased CO2 emissions from forested ecosystems due to changes in forest growth and productivity.
• Tangible benefits of forests for people: changes in tree cover; changes in socio-economic resilience; changes in availability of specific forest products (timber, non-timber wood products and fuel wood, wild foods, medicines, and other non-wood forest products).
• Intangible services provided by forests: changes in the incidence of conflicts between humans and wildlife; changes in the livelihoods of forest-dependent peoples (also a tangible benefit); changes in socio-economic resilience; changes in the cultural, religious and spiritual values associated with particular forests.

Productivity

Increasing CO2 concentration can affect tree growth through increased photosynthetic rates and through improved water-use efficiency. There will be complex interactions, however: forest growth rates may well be increased in some cases by rising levels of atmospheric CO2, but rising temperatures, higher evaporation rates and lower rainfall may lower growth rates in other cases (15).

Non-timber products

Increasingly there are concerns about the productivity of non-timber products such as medicines and foods. Relatively little information is available in the scientific literature about the sustainable management of such products, and even less is known about their vulnerability to climate change (24).

Vulnerabilities – Temperate forests in Europe

Present situation

In parts of Europe with temperate forests, annual mean temperatures are below 17°C but above 6°C, and annual precipitation is at least 500 mm and there is a markedly cool winter period (4). Temperate forests are dominated by broad-leaf species with smaller amounts of evergreen broad-leaf and needle-leaf species (5). Common species include the oaks, eucalypts, acacias, beeches, pines, and birches.

Many of the major factors that influence these forests are due to human activities, including land-use and landscape fragmentation, pollution, soil nutrients and chemistry, fire suppression, alteration to herbivore populations, species loss, alien invasive species, and now climate change (6).

Forest productivity has been increasing in western Europe (7). This is thought to be from increasing CO2 in the atmosphere (8), anthropogenic nitrogen deposition (9), warming temperatures (10), and associated longer growing seasons (11).

Trends

Most models predict continuing trends of modestly increasing forest productivity in Western Europe over this century (12). Projections for the time near the end of the next century generally suggest decreasing growth and a reduction in primary productivity enhancement as temperatures warm, CO2 saturation is reached for photosynthetic enhancement, and reduced summer precipitation all interact to decrease temperate zone primary productivity (13). The projected increased occurrence of pests, particularly in drought-stressed regions, also contributes to decreased long-term primary productivity in some regions of temperate forests  (14).

Sensitivity to increasing air pollution loads, particularly nitrogen deposition and tropospheric ozone, will impact large areas of the northern temperate forest over the next century. In the temperate domain, air pollution is expected to interact with climate change; while the fertilization effects from nitrogen deposition are still highly uncertain, pollutants such as ozone are known to diminish primary productivity (15).

Migration

The ranges of northern temperate forests are predicted to extend into the boreal forest range in the north and upward on mountains (16). The distribution of temperate broadleaved tree species is typically limited by low winter temperatures (17). Since the latter are projected to rise more rapidly than summer temperatures in Europe and North America, temperate broad-leaved tree species may profit and invade currently boreal areas more rapidly than other temperate species.

Carbon sinks/sources

Temperate forest regions in the highly productive forests of western Europe (18) are known to be robust carbon sinks, although increased temperature may reduce this effect through loss of carbon from soils (19). Weaker carbon sinks or even carbon losses are seen for temperate forests in areas prone to periodic drought, such as southern Europe (20).

Models suggest that the greatest climate change threat to temperate forest ecosystems is reduced summer precipitation, leading to increased frequency and severity of drought (21). This will probably be most prominent in temperate forest regions that have already been characterized as prone to drought stress, such as southern Europe. Drought-stricken forests are also more susceptible to opportunistic pests and fire (22). Together, these related effects can potentially change large areas of temperate forest ecosystems from carbon sinks to sources.

Benefits from climate change

Globally, based on both satellite and ground-based data, climatic changes seemed to have a generally positive impact on forest productivity since the middle of the 20th century, when water was not limiting (31).

With the present climate change scenario wood production in Denmark tends to increase further, additionally promoted by the increasing atmospheric CO2-concentration. Furthermore, the Danish forested area grows by approximately 1% on an annual basis due to afforestation efforts aiming at doubling the forest area within 80 to 100 years. The expected changes in climate could increase forest production, particularly if clones, provenances and species are planted and managed that we have no doubts about in relation to health responses to these changes (3).

Timber production in Europe

Climate change will probably increase timber production and reduce prices for wood products in Europe. For 2000–2050 a change of timber production in Europe is expected of -4 to +5%. For 2050–2100 an increase is expected of +2 to +13% (23).

Adaptation strategies

Changes in forest management practices could be one way to adapt. Already today, the National Forest Programme, the Forest Act, and associated support schemes, are assisting in the development of more robust forests, making them more flexible and tolerant towards changing climate variables, for instance precipitation (1,32).

The Forest Act promotes sustainable forest management, in as much as it includes subsidy schemes aimed at private forestry, supporting the use of more robust hardwood species, well-suited provenances and cultivation of varied forests with subsidies for good, diversified forestry and afforestation, for example. Furthermore, in connection with granting support for afforestation after storm damage, provisions have been made that new forests must be cultivated with structures and species that can withstand high wind speeds (2).

Since 2005, the national forests have been undergoing a changeover to close-to-nature forestry, which includes greater use of better adapted tree species, assurance of genetic diversity and changing to stable forest cultivation methods. At the present rate, 50% of national forests will have converted to close-to-nature forestry by around 2050. The conversion will be reassessed within the next 10 years in light of new knowledge of climate developments, tree species, etc (2).

In general, management has to change from the classical mono-species and even-aged management of stands into close-to-nature management characterized by more single tree management incorporation and supporting the natural processes such as regeneration and differentiation and aiming at structural differentiation (3).

Adaptation strategies - Forest management measures in general

Near-nature forest management and a move away from monocultures toward mixed forest types, in terms of both species and age classes, are advocated. In addition, natural or imitated natural regeneration is indicated as a method of maintaining genetic diversity, and subsequently reducing vulnerability. For management against extreme disturbances, improvements in fire detection and suppression techniques are recommended, as well as methods for combating pests and diseases. It is reported that through stricter quarantine and sanitary management, the impact of insects and diseases can be minimized. The establishment of migration corridors between forest reserves may aid in the autonomous colonization and migration of species in response to climate change (28).

Adaptive management

The terms adaptation and adaptive management are often incorrectly used interchangeably. The former involves making adjustments in response to or in anticipation of climate change whereas the latter describes a management system that may be considered, in itself, to be an adaptation tactic (25). Adaptive management is a systematic process for continually improving management policies and practices by learning from the outcomes of operational programmes (26). It involves recognizing uncertainty and establishing methodologies to test hypotheses concerning those uncertainties; it uses management as a tool not only to change the system but to learn about the system (27).

Both the climate and forest ecosystems are constantly changing, and managers will need to adapt their strategies as the climate evolves over the long term. An option that might be appropriate today given expected changes over the next 20 years may no longer be appropriate in 20 years’ time. This will require a continuous programme of actions, monitoring and evaluation – the adaptive management approach described above (24).

There is a widespread assumption that the forest currently at a site is adapted to the current conditions, but this ignores the extent to which the climate has changed over the past 200–300 years, and the lag effects that occur in forests. As a result, replacement of a forest by one of the same composition may no longer be a suitable strategy (25).

Adaptation to climate change has started to be incorporated into all levels of governance, from forest management to international forest policy. Often these policies are not adopted solely in response to climate, and may occur in the absence of knowledge about longer-term climate change. They often serve more than one purpose, including food and fuel provision, shelter and minimizing erosion, as well as adapting to changing climatic conditions (28).

Socio-economic and political conditions have significant influences on vulnerability and adaptive capacity. Climate change projections are perceived by many forest managers as too uncertain to support long-term and potentially costly decisions that may be difficult to reverse. Similarly, uncertainty over future policy developments may also constrain action. Finance is a further barrier to implementing adaptation actions in the forest sector (29).

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Denmark.

1. Danish Ministry of the Environment (2005)
2. Danish Government (2008)
3. Kellomäki et al. (2000)
4. Walter (1979), in: Fischlin (ed.) (2009)
5. Melillo et al. (1993), in: Fischlin (ed.) (2009)
6. Reich and Frelich (2002), in: Fischlin (ed.) (2009)
7. Carrer and Urbinati (2006), in: Fischlin (ed.) (2009)
8. Field et al. (2007b), in: Fischlin (ed.) (2009)
9. Hyvönen et al. (2007); Magnani et al. (2007), both in: Fischlin (ed.) (2009)
10. Marshall et al. (2008), in: Fischlin (ed.) (2009)
11. Chmielewski and Rötzer (2001); Parmesan (2006), both in: Fischlin (ed.) (2009)
12. Alcamo et al. (2007); Field et al. (2007b); Alo and Wang (2008), all in: Fischlin (ed.) (2009)
13. Lucht et al. (2006); Scholze et al. (2006); Alo and Wang (2008), all in: Fischlin (ed.) (2009)
14. Williams et al. (2000); Williams and Liebhold (2002); Logan and Powell (2001); Tran et al. (2007); Friedenberg et al. (2008), all in: Fischlin (ed.) (2009)
15. Fischlin (ed.) (2009)
16. Iverson and Prasad (2001); Ohlemüller et al. (2006); Fischlin et al. (2007); Golubyatnikov and Denisenko (2007), all in: Fischlin (ed.) (2009)
17. Perry et al. (2008), in: Fischlin (ed.) (2009)
18. Liski et al. (2002), in: Fischlin (ed.) (2009)
19. Piao et al. (2008), in: Fischlin (ed.) (2009)
20. Morales et al. (2007), in: Fischlin (ed.) (2009)
21. Christensen et al. (2007); Fischlin et al. (2007); Meehl et al. (2007); Schneider et al. (2007), all in: Fischlin (ed.) (2009)
22. Hanson and Weltzin (2000), in: Fischlin (ed.) (2009)
23. Karjalainen et al. (2003); Nabuurs et al. (2002); Perez-Garcia et al. (2002); Sohngen et al. (2001), in: Osman-Elasha and Parrotta (2009)
24. Innes (ed.) (2009)
25. Ogden and Innes (2007), in: Innes (ed.) (2009)
26. BCMOF (2006a), in: Innes (ed.) (2009)
27. Holling (1978); Lee (1993, 2001), all in: Innes (ed.) (2009)
28. Roberts (ed.) (2009)
29. Keskitalo (2008), in: Roberts (ed.) (2009)
30. Kirilenko and Sedjo (2007)
31. Boisvenue et al. (2006)
32. Danish Ministry of Climate and Energy (2010)
33. Schelhaas et al. (2010)