Forestry vulnerabilities - Overview

The increased vulnerability of forests (and people) with respect to climate change refers to several impacts (26,32):

• 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.

Climate change in the Netherlands will not only affect growth (positive) of trees but also the competitiveness in mixed forests and thereby the species composition (shifts). The direction of change will depend heavily on locality. Thus, the effects of wetter winters and drier summers are very dependent on soil type. So far no doom scenarios are foreseen. However, it does seem certain that more frequently occurring storms will be at the expense of certain species (5).

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 (17).

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 (26).

Peatlands vulnerabilities - Overview

In the Netherlands land subsidence is a continuously ongoing process due to (1) drainage of peatlands and areas reclaimed from the sea, (2) expansion of built-up areas and the infrastructural network on soft soil, and (3) salt mining and gas extraction. This subsidence will continue up to several mm's and locally even cm's per year, depending on the location in The Netherlands (34).

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 (6). Temperate forests are dominated by broad-leaf species with smaller amounts of evergreen broad-leaf and needle-leaf species (7). 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 (8).

Forest productivity has been increasing in western Europe (9). This is thought to be from increasing CO2 in the atmosphere (10), anthropogenic nitrogen deposition (11), warming temperatures (12), and associated longer growing seasons (13).

Trends

Most models predict continuing trends of modestly increasing forest productivity in Western Europe over this century (14). 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 (15). 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  (16).

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 (17).

Migration

The ranges of northern temperate forests are predicted to extend into the boreal forest range in the north and upward on mountains (18). The distribution of temperate broadleaved tree species is typically limited by low winter temperatures (19). 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 (20) are known to be robust carbon sinks, although increased temperature may reduce this effect through loss of carbon from soils (21). Weaker carbon sinks or even carbon losses are seen for temperate forests in areas prone to periodic drought, such as southern Europe (22).

Models suggest that the greatest climate change threat to temperate forest ecosystems is reduced summer precipitation, leading to increased frequency and severity of drought (23). 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 (24). Together, these related effects can potentially change large areas of temperate forest ecosystems from carbon sinks to sources.

Benefits

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 (33).

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% (25).

Adaptation strategies

A number of measures and strategies can be implemented to adapt Dutch forests to the impact of climate change (1):

• Increasing genetic and species diversity in forests. Promoting broad genetic variation and diversified species composition in forests are appropriate strategies to spread the risk of extinction of species and to increase the resilience of production forests. Diverse forests are stable and less susceptible to storms and pest and diseases, and have a higher value for nature and recreation. Forests with higher species diversity have a higher recreational value. Effects of changing genetic and species diversity in production forests are expected on the nature and recreation sectors and on the industrial sector through the supply of different timber species.
• Introduction of southern provenances of tree species and drought resistant species. Examples of southern species are the walnut tree, Robinia, maple, hornbeam, plane tree and several species of lime tree (2). Introduction of new species will require investments in plant material. Moreover the processing industry may have to adapt to the new wood supply. It is unclear what the effect of new species on the pressure of pest and diseases will be.
• Limiting the import of timber. The northbound spread of pests and diseases from southern regions can be slowed by restricting import of fresh timber from areas with pests (2,3).
• Retention of winter precipitation in forests. Winter precipitation retained in forests may be used to relieve drought stress during dry summers (2,4).
• Acceptation of changes in species composition. The acceptation of changes in species composition with respect to the natural, recreational and production functions of forests seems an unavoidable strategy to adapt to climate and the change in species composition is also part of the natural process of forest development (4). More natural and better adapted forests require acceptance of a dynamic species composition and acceptance of associated costs with changed commercial value of production wood, as new timber species may not fit the demands of the timber processing industry.
• Afforestation and adjustment of mix of tree species. Afforestation can contribute to create new green areas and increase the robustness of existing forest ecosystems. New forest areas will also counteract the loss of forest caused by excessive drought in summer. When planting a forest, particular attention should be given to the selection of species. … Currently, each year between 500-1000 ha of new forest is being established. … New plantation forests provide various benefits: they can play an important role in maintaining and/or enhancing genetic variation in the forest, can provide space to several plants and animals living in the forest and can contribute to the expansion of ecological corridors. Moreover the new forest land can provide carbon sequestration and recreation opportunities and support the economy of the country by increasing the annual timber production.
• Adjustment of forest management. For example a switch from single-stand to mixed forests, a switch from drought sensitive species to more resistant species and the use of a more broad range of species will help to spread the risk of possible negative effects. Pest control measures should be taken into account in order to counteract the increase of pests and contain diseases. Trees under stress from drought are more likely to suffer from the attacks of pathogens. Management practices should take into account fire prevention measures (e.g. thinning, removal of leaves, firebreaks).

In the forestry and fishery sectors adaptation is currently not yet part of existing operational management, but it is becoming more important in long term visions. Changing from production forest to multi-functional forests offers opportunities to factor in climate change as a possible driver in decisions related to selection of tree species and definition of management regime (1).

Production forests in the Netherlands are of limited economic importance as far as timber production is concerned. Most adaptation strategies will have to integrate other functions, besides production, to be economically feasible in Dutch economic conditions (1).

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 (30).

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 (27). Adaptive management is a systematic process for continually improving management policies and practices by learning from the outcomes of operational programmes (28). 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 (29).

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 (26).

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 (26).

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 (30).

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 (31).

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 the Netherlands.

1. Nillesen and Van Ierland (2006)
2. Kramer (2001),in: Nillesen and Van Ierland (2006)
3. Parry et al. (2000),in: Nillesen and Van Ierland (2006)
4. Van Ierland et al. (2001),in: Nillesen and Van Ierland (2006)
5. Ministry of Housing, Spatial Planning and the Environment (2009)
6. Walter (1979), in: Fischlin (ed.) (2009)
7. Melillo et al. (1993), in: Fischlin (ed.) (2009)
8. Reich and Frelich (2002), in: Fischlin (ed.) (2009)
9. Carrer and Urbinati (2006), in: Fischlin (ed.) (2009)
10. Field et al. (2007b), in: Fischlin (ed.) (2009)
11. Hyvönen et al. (2007); Magnani et al. (2007), both in: Fischlin (ed.) (2009)
12. Marshall et al. (2008), in: Fischlin (ed.) (2009)
13. Chmielewski and Rötzer (2001); Parmesan (2006), both in: Fischlin (ed.) (2009)
14. Alcamo et al. (2007); Field et al. (2007b); Alo and Wang (2008), all in: Fischlin (ed.) (2009)
15. Lucht et al. (2006); Scholze et al. (2006); Alo and Wang (2008), all in: Fischlin (ed.) (2009)
16. 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)
17. Fischlin (ed.) (2009)
18. Iverson and Prasad (2001); Ohlemüller et al. (2006); Fischlin et al. (2007); Golubyatnikov and Denisenko (2007), all in: Fischlin (ed.) (2009)
19. Perry et al. (2008), in: Fischlin (ed.) (2009)
20. Liski et al. (2002), in: Fischlin (ed.) (2009)
21. Piao et al. (2008), in: Fischlin (ed.) (2009)
22. Morales et al. (2007), in: Fischlin (ed.) (2009)
23. Christensen et al. (2007); Fischlin et al. (2007); Meehl et al. (2007); Schneider et al. (2007), all in: Fischlin (ed.) (2009)
24. Hanson and Weltzin (2000), in: Fischlin (ed.) (2009)
25. Karjalainen et al. (2003); Nabuurs et al. (2002); Perez-Garcia et al. (2002); Sohngen et al. (2001), in: Osman-Elasha and Parrotta (2009)
26. Innes (ed.) (2009)
27. Ogden and Innes (2007), in: Innes (ed.) (2009)
28. BCMOF (2006a), in: Innes (ed.) (2009)
29. Holling (1978); Lee (1993, 2001), all in: Innes (ed.) (2009)
30. Roberts (ed.) (2009)
31. Keskitalo (2008), in: Roberts (ed.) (2009)
32. Kirilenko and Sedjo (2007)
33. Boisvenue et al. (2006)
34. Stouthamer et al. (2020)